diff --git a/drivers.xml b/drivers.xml index dc2f7471214..7085e54ae2c 100644 --- a/drivers.xml +++ b/drivers.xml @@ -2,10 +2,10 @@ - + - https://chromedriver.storage.googleapis.com/77.0.3865.40/chromedriver_win32.zip - c367947ec475e436e34f3f9c4864ae3659867c6e + https://chromedriver.storage.googleapis.com/78.0.3904.70/chromedriver_win32.zip + 26705e683632c6e1f9c62179b6143b409f4d7681 sha1 @@ -13,10 +13,10 @@ - + - https://chromedriver.storage.googleapis.com/77.0.3865.40/chromedriver_linux64.zip - 1776fe8449489fa98e4fe80255ed3874f94d0dee + https://chromedriver.storage.googleapis.com/78.0.3904.70/chromedriver_linux64.zip + 63e13e5f0df96af1cc3a2006c00b2f1871b62caf sha1 @@ -24,10 +24,10 @@ - + - https://chromedriver.storage.googleapis.com/77.0.3865.40/chromedriver_mac64.zip - bc5d502044c86fbba20614df317cc2194d19aa86 + https://chromedriver.storage.googleapis.com/78.0.3904.70/chromedriver_mac64.zip + ce06a7d3a9d18b3d054d3b4c3c32d2cd74e81a91 sha1 diff --git a/flow-bom/pom.xml b/flow-bom/pom.xml index 34490defb70..dd5e0a0fe55 100644 --- a/flow-bom/pom.xml +++ b/flow-bom/pom.xml @@ -38,6 +38,11 @@ flow-html-components ${project.version} + + com.vaadin + flow-server-production-mode + ${project.version} + com.vaadin flow-html-components-testbench diff --git a/flow-client/pom.xml b/flow-client/pom.xml index 2d8594ce46a..17010a1343c 100644 --- a/flow-client/pom.xml +++ b/flow-client/pom.xml @@ -194,6 +194,7 @@ FF38 300 + -Xmx512m -Dvaadin.enableDevServer=false diff --git a/flow-client/src/main/java/com/vaadin/client/ResourceLoader.java b/flow-client/src/main/java/com/vaadin/client/ResourceLoader.java index 365ad034a63..2248bc78a9b 100644 --- a/flow-client/src/main/java/com/vaadin/client/ResourceLoader.java +++ b/flow-client/src/main/java/com/vaadin/client/ResourceLoader.java @@ -771,13 +771,14 @@ private static native void runPromiseExpression(String expression, /*-{ try { var promise = promiseSupplier.@java.util.function.Supplier::get(*)(); - if ( !(promise instanceof Promise )){ + if ( !(promise instanceof $wnd.Promise )){ throw new Error('The expression "'+expression+'" result is not a Promise.'); } promise.then( function(result) { onSuccess.@java.lang.Runnable::run(*)(); } , - function(error) { onError.@java.lang.Runnable::run(*)(); } ); + function(error) { console.error(error); onError.@java.lang.Runnable::run(*)(); } ); } catch(error) { + console.error(error); onError.@java.lang.Runnable::run(*)(); } }-*/; diff --git a/flow-client/src/main/java/com/vaadin/client/communication/DefaultConnectionStateHandler.java b/flow-client/src/main/java/com/vaadin/client/communication/DefaultConnectionStateHandler.java index 36dd41e37f8..93d8a1d174c 100644 --- a/flow-client/src/main/java/com/vaadin/client/communication/DefaultConnectionStateHandler.java +++ b/flow-client/src/main/java/com/vaadin/client/communication/DefaultConnectionStateHandler.java @@ -24,6 +24,7 @@ import com.vaadin.client.Console; import com.vaadin.client.Registry; +import com.vaadin.client.UILifecycle; import com.vaadin.client.UILifecycle.UIState; import com.vaadin.client.WidgetUtil; import com.vaadin.client.communication.AtmospherePushConnection.AtmosphereResponse; @@ -297,7 +298,10 @@ protected void updateDialog() { */ protected final void giveUp() { reconnectionCause = null; - endRequest(); + + if (registry.getRequestResponseTracker().hasActiveRequest()) { + endRequest(); + } stopDialogTimer(); if (!isDialogVisible()) { @@ -468,7 +472,12 @@ protected void handleUnauthorized(XhrConnectionError xhrConnectionError) { private void stopApplication() { // Consider application not running any more and prevent all // future requests - registry.getUILifecycle().setState(UIState.TERMINATED); + + UILifecycle uiLifecycle = registry.getUILifecycle(); + + if (uiLifecycle.getState() != UIState.TERMINATED) { + uiLifecycle.setState(UIState.TERMINATED); + } } private void handleUnrecoverableCommunicationError(String details, diff --git a/flow-client/src/main/java/com/vaadin/client/communication/MessageHandler.java b/flow-client/src/main/java/com/vaadin/client/communication/MessageHandler.java index be0e0491102..15725cd1a82 100644 --- a/flow-client/src/main/java/com/vaadin/client/communication/MessageHandler.java +++ b/flow-client/src/main/java/com/vaadin/client/communication/MessageHandler.java @@ -18,6 +18,7 @@ import com.google.gwt.core.client.Duration; import com.google.gwt.core.client.Scheduler; import com.google.gwt.user.client.Timer; + import com.vaadin.client.Command; import com.vaadin.client.Console; import com.vaadin.client.DependencyLoader; @@ -190,8 +191,15 @@ public void handleMessage(final ValueMap json) { "The json to handle cannot be null"); } if (getServerId(json) == -1) { - Console.error("Response didn't contain a server id. " - + "Please verify that the server is up-to-date and that the response data has not been modified in transmission."); + + ValueMap meta = json.getValueMap("meta"); + + // Log the error only if session didn't expire. + if (meta == null + || !meta.containsKey(JsonConstants.META_SESSION_EXPIRED)) { + Console.error("Response didn't contain a server id. " + + "Please verify that the server is up-to-date and that the response data has not been modified in transmission."); + } } UIState state = registry.getUILifecycle().getState(); @@ -502,7 +510,7 @@ private boolean isResynchronize(ValueMap json) { private boolean isResponse(ValueMap json) { ValueMap meta = json.getValueMap("meta"); - if (meta == null || !meta.containsKey("async")) { + if (meta == null || !meta.containsKey(JsonConstants.META_ASYNC)) { return true; } return false; diff --git a/flow-client/src/main/java/com/vaadin/client/communication/ServerConnector.java b/flow-client/src/main/java/com/vaadin/client/communication/ServerConnector.java index f2ee8a09121..6b5032159c2 100644 --- a/flow-client/src/main/java/com/vaadin/client/communication/ServerConnector.java +++ b/flow-client/src/main/java/com/vaadin/client/communication/ServerConnector.java @@ -122,15 +122,21 @@ public void sendEventMessage(int nodeId, String eventType, * the event handler method name to execute on the server side * @param argsArray * the arguments array for the method + * @param promiseId + * the promise id to use for getting the result back, or -1 if no + * result is expected */ public void sendTemplateEventMessage(StateNode node, String methodName, - JsonArray argsArray) { + JsonArray argsArray, int promiseId) { JsonObject message = Json.createObject(); message.put(JsonConstants.RPC_TYPE, JsonConstants.RPC_PUBLISHED_SERVER_EVENT_HANDLER); message.put(JsonConstants.RPC_NODE, node.getId()); message.put(JsonConstants.RPC_TEMPLATE_EVENT_METHOD_NAME, methodName); message.put(JsonConstants.RPC_TEMPLATE_EVENT_ARGS, argsArray); + if (promiseId != -1) { + message.put(JsonConstants.RPC_TEMPLATE_EVENT_PROMISE, promiseId); + } sendMessage(message); } diff --git a/flow-client/src/main/java/com/vaadin/client/flow/StateTree.java b/flow-client/src/main/java/com/vaadin/client/flow/StateTree.java index 2b8c7b05f97..6f99e8592da 100644 --- a/flow-client/src/main/java/com/vaadin/client/flow/StateTree.java +++ b/flow-client/src/main/java/com/vaadin/client/flow/StateTree.java @@ -245,13 +245,16 @@ public void sendNodePropertySyncToServer(MapProperty property) { * the method name * @param argsArray * the arguments array for the method + * @param promiseId + * the promise id to use for getting the result back, or -1 if no + * result is expected */ public void sendTemplateEventToServer(StateNode node, String methodName, - JsArray argsArray) { + JsArray argsArray, int promiseId) { if (isValidNode(node)) { JsonArray array = WidgetUtil.crazyJsCast(argsArray); registry.getServerConnector().sendTemplateEventMessage(node, - methodName, array); + methodName, array, promiseId); } } diff --git a/flow-client/src/main/java/com/vaadin/client/flow/binding/ServerEventHandlerBinder.java b/flow-client/src/main/java/com/vaadin/client/flow/binding/ServerEventHandlerBinder.java index ca65292f96f..55dca50815a 100644 --- a/flow-client/src/main/java/com/vaadin/client/flow/binding/ServerEventHandlerBinder.java +++ b/flow-client/src/main/java/com/vaadin/client/flow/binding/ServerEventHandlerBinder.java @@ -52,7 +52,7 @@ private ServerEventHandlerBinder() { public static EventRemover bindServerEventHandlerNames(Element element, StateNode node) { return bindServerEventHandlerNames(() -> ServerEventObject.get(element), - node, NodeFeatures.CLIENT_DELEGATE_HANDLERS); + node, NodeFeatures.CLIENT_DELEGATE_HANDLERS, true); } /** @@ -67,11 +67,15 @@ public static EventRemover bindServerEventHandlerNames(Element element, * the state node containing the feature * @param featureId * the feature id which contains event handler methods + * @param returnValue + * true if the handler should return a promise that + * will reflect the server-side result; false to not + * return any value * @return a handle which can be used to remove the listener for the feature */ public static EventRemover bindServerEventHandlerNames( Supplier objectProvider, StateNode node, - int featureId) { + int featureId, boolean returnValue) { NodeList serverEventHandlerNamesList = node.getList(featureId); if (serverEventHandlerNamesList.length() > 0) { @@ -80,7 +84,7 @@ public static EventRemover bindServerEventHandlerNames( for (int i = 0; i < serverEventHandlerNamesList.length(); i++) { String serverEventHandlerName = (String) serverEventHandlerNamesList .get(i); - object.defineMethod(serverEventHandlerName, node); + object.defineMethod(serverEventHandlerName, node, returnValue); } } @@ -94,7 +98,8 @@ public static EventRemover bindServerEventHandlerNames( JsArray add = e.getAdd(); for (int i = 0; i < add.length(); i++) { - serverObject.defineMethod((String) add.get(i), node); + serverObject.defineMethod((String) add.get(i), node, + returnValue); } }); } diff --git a/flow-client/src/main/java/com/vaadin/client/flow/binding/ServerEventObject.java b/flow-client/src/main/java/com/vaadin/client/flow/binding/ServerEventObject.java index 4985d08c54d..e30cbe82d12 100644 --- a/flow-client/src/main/java/com/vaadin/client/flow/binding/ServerEventObject.java +++ b/flow-client/src/main/java/com/vaadin/client/flow/binding/ServerEventObject.java @@ -15,7 +15,6 @@ */ package com.vaadin.client.flow.binding; - import jsinterop.annotations.JsFunction; import com.google.gwt.core.client.JavaScriptObject; @@ -28,6 +27,7 @@ import com.vaadin.client.flow.collection.JsMap; import com.vaadin.client.flow.util.NativeFunction; import com.vaadin.flow.internal.nodefeature.NodeFeatures; +import com.vaadin.flow.shared.JsonConstants; import elemental.dom.Element; import elemental.dom.Node; @@ -46,6 +46,8 @@ public final class ServerEventObject extends JavaScriptObject { private static final String NODE_ID = "nodeId"; private static final String EVENT_PREFIX = "event"; + private static final String PROMISE_CALLBACK_NAME = JsonConstants.RPC_PROMISE_CALLBACK_NAME; + /** * Callback interface for an event data expression parsed using new * Function() in JavaScript. @@ -76,6 +78,31 @@ private interface ServerEventDataExpression { protected ServerEventObject() { } + private native void initPromiseHandler() + /*-{ + var name = @ServerEventObject::PROMISE_CALLBACK_NAME + // Use defineProperty to make it non-enumerable + Object.defineProperty(this, name, { + value: function(promiseId, success, value) { + var promise = this[name].promises[promiseId]; + + // undefined if client-side node was recreated after execution was scheduled + if (promise !== undefined) { + delete this[name].promises[promiseId]; + + if (success) { + // Resolve + promise[0](value); + } else { + // Reject + promise[1](Error("Something went wrong. Check server-side logs for more information.")); + } + } + } + }); + this[name].promises = []; + }-*/; + /** * Defines a method with the given name to be a callback to the server for * the given state node. @@ -88,8 +115,13 @@ protected ServerEventObject() { * @param node * the node to use as an identifier when sending an event to the * server + * @param returnPromise + * true if the handler should return a promise that + * will reflect the server-side result; false to not + * return any value */ - public native void defineMethod(String methodName, StateNode node) + public native void defineMethod(String methodName, StateNode node, + boolean returnPromise) /*-{ this[methodName] = $entry(function(eventParameter) { var prototype = Object.getPrototypeOf(this); @@ -102,7 +134,24 @@ public native void defineMethod(String methodName, StateNode node) if(args === null) { args = Array.prototype.slice.call(arguments); } - tree.@com.vaadin.client.flow.StateTree::sendTemplateEventToServer(*)(node, methodName, args); + + var returnValue; + var promiseId = -1; + + if (returnPromise) { + var promises = this[@ServerEventObject::PROMISE_CALLBACK_NAME].promises; + + promiseId = promises.length; + + returnValue = new Promise(function(resolve, reject) { + // Store each callback for later use + promises[promiseId] = [resolve, reject]; + }); + } + + tree.@com.vaadin.client.flow.StateTree::sendTemplateEventToServer(*)(node, methodName, args, promiseId); + + return returnValue; }); }-*/; @@ -230,6 +279,7 @@ public static ServerEventObject get(Element element) { .crazyJsoCast(WidgetUtil.getJsProperty(element, "$server")); if (serverObject == null) { serverObject = (ServerEventObject) JavaScriptObject.createObject(); + serverObject.initPromiseHandler(); WidgetUtil.setJsProperty(element, "$server", serverObject); } return serverObject; diff --git a/flow-client/src/main/java/com/vaadin/client/flow/binding/SimpleElementBindingStrategy.java b/flow-client/src/main/java/com/vaadin/client/flow/binding/SimpleElementBindingStrategy.java index 776a42ec72b..4eea8b15b8b 100644 --- a/flow-client/src/main/java/com/vaadin/client/flow/binding/SimpleElementBindingStrategy.java +++ b/flow-client/src/main/java/com/vaadin/client/flow/binding/SimpleElementBindingStrategy.java @@ -19,8 +19,11 @@ import java.util.function.Consumer; import java.util.function.Supplier; +import jsinterop.annotations.JsFunction; + import com.google.gwt.core.client.JavaScriptObject; import com.google.gwt.core.client.Scheduler; + import com.vaadin.client.Command; import com.vaadin.client.Console; import com.vaadin.client.ExistingElementMap; @@ -62,7 +65,6 @@ import elemental.json.JsonObject; import elemental.json.JsonType; import elemental.json.JsonValue; -import jsinterop.annotations.JsFunction; /** * Binding strategy for a simple (not template) {@link Element} node. @@ -257,8 +259,14 @@ private void scheduleInitialExecution(StateNode stateNode) { * command execution */ Reactive.addPostFlushListener( - () -> Scheduler.get().scheduleDeferred(() -> stateNode - .getNodeData(InitialPropertyUpdate.class).execute())); + () -> Scheduler.get().scheduleDeferred(() -> { + InitialPropertyUpdate propertyUpdate = stateNode + .getNodeData(InitialPropertyUpdate.class); + // cleared if handlePropertiesChanged has already happened + if (propertyUpdate != null) { + propertyUpdate.execute(); + } + })); } private native void bindPolymerModelProperties(StateNode node, @@ -284,9 +292,9 @@ private native void bindPolymerModelProperties(StateNode node, private native void hookUpPolymerElement(StateNode node, Element element) /*-{ var self = this; - + var originalPropertiesChanged = element._propertiesChanged; - + if (originalPropertiesChanged) { element._propertiesChanged = function (currentProps, changedProps, oldProps) { $entry(function () { @@ -295,16 +303,16 @@ private native void hookUpPolymerElement(StateNode node, Element element) originalPropertiesChanged.apply(this, arguments); }; } - - + + var tree = node.@com.vaadin.client.flow.StateNode::getTree()(); - + var originalReady = element.ready; - + element.ready = function (){ originalReady.apply(this, arguments); @com.vaadin.client.PolymerUtils::fireReadyEvent(*)(element); - + // The _propertiesChanged method which is replaced above for the element // doesn't do anything for items in dom-repeat. // Instead it's called with some meaningful info for the dom-repeat element. @@ -313,7 +321,7 @@ private native void hookUpPolymerElement(StateNode node, Element element) // which changes this method for any dom-repeat instance. var replaceDomRepeatPropertyChange = function(){ var domRepeat = element.root.querySelector('dom-repeat'); - + if ( domRepeat ){ // If the dom-repeat element is in the DOM then // this method should not be executed anymore. The logic below will replace @@ -327,12 +335,12 @@ private native void hookUpPolymerElement(StateNode node, Element element) // if dom-repeat is found => replace _propertiesChanged method in the prototype and mark it as replaced. if ( !domRepeat.constructor.prototype.$propChangedModified){ domRepeat.constructor.prototype.$propChangedModified = true; - + var changed = domRepeat.constructor.prototype._propertiesChanged; - + domRepeat.constructor.prototype._propertiesChanged = function(currentProps, changedProps, oldProps){ changed.apply(this, arguments); - + var props = Object.getOwnPropertyNames(changedProps); var items = "items."; var i; @@ -353,7 +361,7 @@ private native void hookUpPolymerElement(StateNode node, Element element) if( currentPropsItem && currentPropsItem.nodeId ){ var nodeId = currentPropsItem.nodeId; var value = currentPropsItem[propertyName]; - + // this is an attempt to find the template element // which is not available as a context in the protype method var host = this.__dataHost; @@ -364,7 +372,7 @@ private native void hookUpPolymerElement(StateNode node, Element element) while( !host.localName || host.__dataHost ){ host = host.__dataHost; } - + $entry(function () { @SimpleElementBindingStrategy::handleListItemPropertyChange(*)(nodeId, host, propertyName, value, tree); })(); @@ -375,7 +383,7 @@ private native void hookUpPolymerElement(StateNode node, Element element) }; } }; - + // dom-repeat doesn't have to be in DOM even if template has it // such situation happens if there is dom-if e.g. which evaluates to false initially. // in this case dom-repeat is not yet in the DOM tree until dom-if becomes true @@ -390,7 +398,7 @@ private native void hookUpPolymerElement(StateNode node, Element element) element.addEventListener('dom-change',replaceDomRepeatPropertyChange); } } - + }-*/; private static void handleListItemPropertyChange(double nodeId, @@ -1379,7 +1387,7 @@ private EventRemover bindClassList(Element element, StateNode node) { private EventRemover bindPolymerEventHandlerNames(BindingContext context) { return ServerEventHandlerBinder.bindServerEventHandlerNames( () -> WidgetUtil.crazyJsoCast(context.htmlNode), context.node, - NodeFeatures.POLYMER_SERVER_EVENT_HANDLERS); + NodeFeatures.POLYMER_SERVER_EVENT_HANDLERS, false); } private EventRemover bindClientCallableMethods(BindingContext context) { diff --git a/flow-client/src/test-gwt/java/com/vaadin/client/ClientEngineTestBase.java b/flow-client/src/test-gwt/java/com/vaadin/client/ClientEngineTestBase.java index 7f6d878801c..984c371c123 100644 --- a/flow-client/src/test-gwt/java/com/vaadin/client/ClientEngineTestBase.java +++ b/flow-client/src/test-gwt/java/com/vaadin/client/ClientEngineTestBase.java @@ -10,7 +10,7 @@ public abstract class ClientEngineTestBase extends GWTTestCase { @Override protected void gwtSetUp() throws Exception { - installCollectionsPolyfill(); + installPolyfills(); super.gwtSetUp(); } @@ -19,7 +19,7 @@ public String getModuleName() { return "com.vaadin.ClientEngineXSI"; } - private static native void installCollectionsPolyfill() + private static native void installPolyfills() /*-{ // Remove broken HtmlUnit versions (polyfill checks window, but installs to $wnd) delete window.Set; @@ -34,6 +34,13 @@ private static native void installCollectionsPolyfill() 0}function z(){return k(this._itp,this._keys)}function l(){return k(this._itp,this._values)}function A(){return k(this._itp,this._keys,this._values)}function B(){return k(this._itp,this._values,this._values)}function k(a,c,b){var g=[0],e=!1;a.push(g);return{next:function(){var f,d=g[0];!e&&dn;n++)r(e,e._deferreds[n]);e._deferreds=null}function c(e,n){var t=!1;try{e(function(e){t||(t=!0,i(n,e))},function(e){t||(t=!0,f(n,e))})}catch(o){if(t)return;t=!0,f(n,o)}}var a=setTimeout;o.prototype["catch"]=function(e){return this.then(null,e)},o.prototype.then=function(e,n){var o=new this.constructor(t);return r(this,new function(e,n,t){this.onFulfilled="function"==typeof e?e:null,this.onRejected="function"==typeof n?n:null,this.promise=t}(e,n,o)),o},o.prototype["finally"]=e,o.all=function(e){return new o(function(t,o){function r(e,n){try{if(n&&("object"==typeof n||"function"==typeof n)){var u=n.then;if("function"==typeof u)return void u.call(n,function(n){r(e,n)},o)}i[e]=n,0==--f&&t(i)}catch(c){o(c)}}if(!n(e))return o(new TypeError("Promise.all accepts an array"));var i=Array.prototype.slice.call(e);if(0===i.length)return t([]);for(var f=i.length,u=0;i.length>u;u++)r(u,i[u])})},o.resolve=function(e){return e&&"object"==typeof e&&e.constructor===o?e:new o(function(n){n(e)})},o.reject=function(e){return new o(function(n,t){t(e)})},o.race=function(e){return new o(function(t,r){if(!n(e))return r(new TypeError("Promise.race accepts an array"));for(var i=0,f=e.length;f>i;i++)o.resolve(e[i]).then(t,r)})},o._immediateFn="function"==typeof setImmediate&&function(e){setImmediate(e)}||function(e){a(e,0)},o._unhandledRejectionFn=function(e){void 0!==console&&console&&console.warn("Possible Unhandled Promise Rejection:",e)};var l=function(){if("undefined"!=typeof self)return self;if("undefined"!=typeof window)return window;if("undefined"!=typeof global)return global;throw Error("unable to locate global object")}();"Promise"in l?l.Promise.prototype["finally"]||(l.Promise.prototype["finally"]=e):l.Promise=o}); }-*/; } diff --git a/flow-client/src/test-gwt/java/com/vaadin/client/flow/GwtEventHandlerTest.java b/flow-client/src/test-gwt/java/com/vaadin/client/flow/GwtEventHandlerTest.java index 955f987e479..164fca9b702 100644 --- a/flow-client/src/test-gwt/java/com/vaadin/client/flow/GwtEventHandlerTest.java +++ b/flow-client/src/test-gwt/java/com/vaadin/client/flow/GwtEventHandlerTest.java @@ -56,6 +56,7 @@ public class GwtEventHandlerTest extends ClientEngineTestBase { private Map> serverMethods = new HashMap<>(); private Map serverRpcNodes = new HashMap<>(); + private Map serverPromiseIds = new HashMap<>(); @Override protected void gwtSetUp() throws Exception { @@ -72,9 +73,10 @@ protected void gwtSetUp() throws Exception { @Override public void sendTemplateEventToServer(StateNode node, - String methodName, JsArray argValues) { + String methodName, JsArray argValues, int promiseId) { serverMethods.put(methodName, argValues); serverRpcNodes.put(methodName, node); + serverPromiseIds.put(methodName, Integer.valueOf(promiseId)); } }; @@ -91,6 +93,77 @@ public void testNoServerEventHandler_nothingInDom() { assertNull(WidgetUtil.getJsProperty(element, "$server")); } + public void testClientCallablePromises() { + String methodName = "publishedMethod"; + + node.getList(NodeFeatures.CLIENT_DELEGATE_HANDLERS).add(0, methodName); + Binder.bind(node, element); + Reactive.flush(); + ServerEventObject serverObject = ServerEventObject.get(element); + + NativeFunction publishedMethod = new NativeFunction( + "return this." + methodName + "()"); + Object promise0 = publishedMethod.apply(serverObject, + JsCollections.array()); + + assertNotNull(promise0); + assertEquals(Integer.valueOf(0), serverPromiseIds.get(methodName)); + assertTrue(hasPromise(element, 0)); + + Object promise1 = publishedMethod.apply(serverObject, + JsCollections.array()); + assertEquals(Integer.valueOf(1), serverPromiseIds.get(methodName)); + assertTrue(hasPromise(element, 1)); + + addThen(promise0, value -> { + assertEquals("promise0", value); + assertFalse("Promise handlers should be cleared", + hasPromise(element, 0)); + + completePromise(element, 1, false, null); + }); + + addCatch(promise1, message -> { + assertEquals( + "Error: Something went wrong. Check server-side logs for more information.", + message); + assertFalse("Promise handlers should be cleared", + hasPromise(element, 1)); + + finishTest(); + }); + + completePromise(element, 0, true, "promise0"); + + delayTestFinish(100); + } + + private static native void addThen(Object promise, Consumer callback) + /*-{ + promise.then($entry(function(value) { + callback.@Consumer::accept(*)(value); + })); + }-*/; + + private static native void addCatch(Object promise, + Consumer callback) + /*-{ + promise['catch']($entry(function(value) { + callback.@Consumer::accept(*)(""+value); + })); + }-*/; + + private static native void completePromise(Element element, int promiseId, + boolean success, String value) + /*-{ + element.$server[@ServerEventObject::PROMISE_CALLBACK_NAME](promiseId, success, value); + }-*/; + + private static native boolean hasPromise(Element element, int promiseId) + /*-{ + return promiseId in element.$server[@ServerEventObject::PROMISE_CALLBACK_NAME].promises; + }-*/; + public void testClientCallableMethodInDom() { assertServerEventHandlerMethodInDom( NodeFeatures.CLIENT_DELEGATE_HANDLERS, @@ -145,6 +218,7 @@ public void testPolymerMockedEventHandler() { assertEquals(methodName, serverMethods.keySet().iterator().next()); assertEquals(0, serverMethods.get(methodName).length()); assertEquals(node, serverRpcNodes.get(methodName)); + assertEquals(Integer.valueOf(-1), serverPromiseIds.get(methodName)); } public void testPolymerMockedEventHandlerWithEventData() { @@ -219,7 +293,7 @@ public void testPolymerMockedEventHandlerWithDefaultImplementation() { * Add a function to the element prototype ("default" function) for * {@code methodName} that adds the second argument to the event (first * argument) as a result - * + * * @param element * Element to add "default" method to * @param methodName @@ -328,7 +402,7 @@ public void testEventHandlerModelItemSingleItem() { /** * Add get functionality to element if not defined. Add the key value pair * to property object or create object if not available. - * + * * @param node * Target node * @param property diff --git a/flow-client/src/test-gwt/java/com/vaadin/client/flow/GwtMultipleBindingTest.java b/flow-client/src/test-gwt/java/com/vaadin/client/flow/GwtMultipleBindingTest.java index 2a128056d73..0cfe8dca2a3 100644 --- a/flow-client/src/test-gwt/java/com/vaadin/client/flow/GwtMultipleBindingTest.java +++ b/flow-client/src/test-gwt/java/com/vaadin/client/flow/GwtMultipleBindingTest.java @@ -97,7 +97,7 @@ protected void gwtSetUp() throws Exception { tree = new StateTree(registry) { @Override public void sendTemplateEventToServer(StateNode node, - String methodName, JsArray argValues) { + String methodName, JsArray argValues, int promiseId) { } }; diff --git a/flow-client/src/test-gwt/java/com/vaadin/client/flow/GwtStateTreeTest.java b/flow-client/src/test-gwt/java/com/vaadin/client/flow/GwtStateTreeTest.java index b8c97eec824..400874fd9f8 100644 --- a/flow-client/src/test-gwt/java/com/vaadin/client/flow/GwtStateTreeTest.java +++ b/flow-client/src/test-gwt/java/com/vaadin/client/flow/GwtStateTreeTest.java @@ -16,6 +16,7 @@ package com.vaadin.client.flow; import com.google.gwt.core.client.JavaScriptObject; + import com.vaadin.client.ClientEngineTestBase; import com.vaadin.client.InitialPropertiesHandler; import com.vaadin.client.Registry; @@ -50,7 +51,7 @@ private TestServerConnector(Registry registry) { @Override public void sendTemplateEventMessage(StateNode node, String methodName, - JsonArray array) { + JsonArray array, int promiseId) { this.node = node; this.methodName = methodName; args = array; @@ -79,7 +80,7 @@ public void testSendTemplateEventToServer_delegateToServerConnector() { StateNode node = new StateNode(0, tree); tree.registerNode(node); JsArray array = getArgArray(); - tree.sendTemplateEventToServer(node, "foo", array); + tree.sendTemplateEventToServer(node, "foo", array, -1); JsonObject object = Json.createObject(); object.put("key", "value"); @@ -104,7 +105,7 @@ public void testDeferredTemplateMessage_isIgnored() { tree.registerNode(node); Reactive.addPostFlushListener(() -> { - tree.sendTemplateEventToServer(node, "click", null); + tree.sendTemplateEventToServer(node, "click", null, -1); TestServerConnector serverConnector = (TestServerConnector) registry .getServerConnector(); assertNull( diff --git a/flow-data/src/main/java/com/vaadin/flow/data/binder/Binder.java b/flow-data/src/main/java/com/vaadin/flow/data/binder/Binder.java index fbb325d0f02..6263c2a3378 100644 --- a/flow-data/src/main/java/com/vaadin/flow/data/binder/Binder.java +++ b/flow-data/src/main/java/com/vaadin/flow/data/binder/Binder.java @@ -566,9 +566,11 @@ default BindingBuilder withNullRepresentation( TARGET nullRepresentation) { return withConverter( fieldValue -> Objects.equals(fieldValue, nullRepresentation) - ? null : fieldValue, + ? null + : fieldValue, modelValue -> Objects.isNull(modelValue) - ? nullRepresentation : modelValue); + ? nullRepresentation + : modelValue); } /** @@ -2503,7 +2505,8 @@ private Converter createNullRepresentationA Converter nullRepresentationConverter = Converter .from(fieldValue -> fieldValue, modelValue -> Objects.isNull(modelValue) - ? field.getEmptyValue() : modelValue, + ? field.getEmptyValue() + : modelValue, Throwable::getMessage); ConverterDelegate converter = new ConverterDelegate<>( nullRepresentationConverter); @@ -2882,6 +2885,7 @@ protected void removeBindingInternal(Binding binding) { if (bindings.remove(binding)) { boundProperties.entrySet() .removeIf(entry -> entry.getValue().equals(binding)); + changedBindings.remove(binding); } } diff --git a/flow-data/src/main/java/com/vaadin/flow/data/provider/AbstractDataProvider.java b/flow-data/src/main/java/com/vaadin/flow/data/provider/AbstractDataProvider.java index 2b42f40ae55..93d66fe7e14 100644 --- a/flow-data/src/main/java/com/vaadin/flow/data/provider/AbstractDataProvider.java +++ b/flow-data/src/main/java/com/vaadin/flow/data/provider/AbstractDataProvider.java @@ -45,7 +45,16 @@ public abstract class AbstractDataProvider implements DataProvider { @Override public Registration addDataProviderListener( DataProviderListener listener) { - return addListener(DataChangeEvent.class, listener::onDataChange); + // Using an anonymous class instead of lambda or method reference to prevent potential + // self reference serialization issues when clients holds a reference + // to the Registration instance returned by this method + SerializableConsumer consumer = new SerializableConsumer() { + @Override + public void accept(DataChangeEvent dataChangeEvent) { + listener.onDataChange(dataChangeEvent); + } + }; + return addListener(DataChangeEvent.class, consumer); } @Override diff --git a/flow-data/src/test/java/com/vaadin/flow/data/binder/BinderTest.java b/flow-data/src/test/java/com/vaadin/flow/data/binder/BinderTest.java index 2c8258e015d..e953d78e729 100644 --- a/flow-data/src/test/java/com/vaadin/flow/data/binder/BinderTest.java +++ b/flow-data/src/test/java/com/vaadin/flow/data/binder/BinderTest.java @@ -121,6 +121,23 @@ public void bindNullBean_FieldsAreCleared() { assertEquals("Age field not empty", "", ageField.getValue()); } + @Test + public void removeInvalidBinding_validateDoesNotThrow() { + binder.forField(nameField).bind(Person::getFirstName, + Person::setFirstName); + Binding ageBinding = binder.forField(ageField) + .withConverter(new StringToIntegerConverter("")) + .bind(Person::getAge, Person::setAge); + binder.withValidator(bean -> true, ""); + binder.setBean(item); + + ageField.setValue("foo"); + + binder.removeBinding(ageBinding); + + binder.validate(); + } + @Test public void clearForReadBean_boundFieldsAreCleared() { binder.forField(nameField).bind(Person::getFirstName, @@ -451,8 +468,9 @@ public void beanBinder_withConverter_nullRepresentationIsNotDisabled() { String customNullPointerRepresentation = "foo"; Binder binder = new Binder<>(Person.class); binder.forField(nameField) - .withConverter(value -> value, value -> value == null - ? customNullPointerRepresentation : value) + .withConverter(value -> value, + value -> value == null ? customNullPointerRepresentation + : value) .bind("firstName"); Person person = new Person(); @@ -1345,7 +1363,6 @@ public void nullRejetingField_nullValue_wrappedExceptionMentionsNullRepresentati binder.readBean(new AtomicReference<>()); } - @Test public void nullRejetingField_otherRejectedValue_originalExceptionIsThrown() { TestTextField field = createNullRejectingFieldWithEmptyValue(""); diff --git a/flow-data/src/test/java/com/vaadin/flow/tests/data/DataSerializableTest.java b/flow-data/src/test/java/com/vaadin/flow/tests/data/DataSerializableTest.java index b5cedc9cb03..47d28c02de4 100644 --- a/flow-data/src/test/java/com/vaadin/flow/tests/data/DataSerializableTest.java +++ b/flow-data/src/test/java/com/vaadin/flow/tests/data/DataSerializableTest.java @@ -1,6 +1,58 @@ package com.vaadin.flow.tests.data; +import java.io.Serializable; +import java.util.Collections; + +import com.vaadin.flow.data.binder.HasDataProvider; +import com.vaadin.flow.data.provider.DataProvider; +import com.vaadin.flow.data.provider.ListDataProvider; +import com.vaadin.flow.shared.Registration; import com.vaadin.flow.testutil.ClassesSerializableTest; +import org.junit.Test; + +import static org.junit.Assert.assertNotNull; public class DataSerializableTest extends ClassesSerializableTest { + + /* + * AbstractDataProvider.addDataProviderListener may return a Registration instance + * that is not deserializable due to self references. + * This happens for example if the dataprovider, member of a component, + * is used to add a com.vaadin.flow.data.provider.DataProviderListener + * into an inner component; the resulting Registration handles a reference + * to the dataprovider itself that is already referenced by the outer component + */ + @Test + public void selfReferenceSerialization() throws Throwable { + Outer outer = new Outer(); + Outer out = serializeAndDeserialize(outer); + assertNotNull(out); + } + + static class Inner implements HasDataProvider, Serializable { + + private Registration registration; + + @Override + public void setDataProvider(DataProvider dataProvider) { + if (registration != null) { + registration.remove(); + } + registration = dataProvider.addDataProviderListener(event -> onDataProviderChange()); + } + + void onDataProviderChange() { + + } + + } + + static class Outer implements Serializable { + private final ListDataProvider dataProvider = new ListDataProvider<>(Collections.emptyList()); + private final Inner inner = new Inner(); + + public Outer() { + inner.setDataProvider(dataProvider); + } + } } diff --git a/flow-html-components-testbench/src/main/java/com/vaadin/flow/component/html/testbench/PreElement.java b/flow-html-components-testbench/src/main/java/com/vaadin/flow/component/html/testbench/PreElement.java new file mode 100644 index 00000000000..de0568e8e09 --- /dev/null +++ b/flow-html-components-testbench/src/main/java/com/vaadin/flow/component/html/testbench/PreElement.java @@ -0,0 +1,28 @@ +/* + * Copyright 2000-2018 Vaadin Ltd. + * + * Licensed under the Apache License, Version 2.0 (the "License"); you may not + * use this file except in compliance with the License. You may obtain a copy of + * the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT + * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the + * License for the specific language governing permissions and limitations under + * the License. + */ +package com.vaadin.flow.component.html.testbench; + +import com.vaadin.testbench.TestBenchElement; +import com.vaadin.testbench.elementsbase.Element; + +/** + * A TestBench element representing a <pre> element. + * + */ +@Element("pre") +public class PreElement extends TestBenchElement { + +} diff --git a/flow-html-components/src/main/java/com/vaadin/flow/component/html/Pre.java b/flow-html-components/src/main/java/com/vaadin/flow/component/html/Pre.java new file mode 100644 index 00000000000..5de9b817b9a --- /dev/null +++ b/flow-html-components/src/main/java/com/vaadin/flow/component/html/Pre.java @@ -0,0 +1,59 @@ +/* + * Copyright 2000-2018 Vaadin Ltd. + * + * Licensed under the Apache License, Version 2.0 (the "License"); you may not + * use this file except in compliance with the License. You may obtain a copy of + * the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT + * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the + * License for the specific language governing permissions and limitations under + * the License. + */ +package com.vaadin.flow.component.html; + +import com.vaadin.flow.component.ClickNotifier; +import com.vaadin.flow.component.Component; +import com.vaadin.flow.component.HtmlContainer; +import com.vaadin.flow.component.Tag; + +/** + * Component representing a <pre> element. + * + * @author Vaadin Ltd + */ +@Tag(Tag.PRE) +public class Pre extends HtmlContainer + implements ClickNotifier
 {
+
+    /**
+     * Creates a new empty preformatted text block.
+     */
+    public Pre() {
+        super();
+    }
+
+    /**
+     * Creates a new preformatted text block with the given child components.
+     *
+     * @param components
+     *            the child components
+     */
+    public Pre(Component... components) {
+        super(components);
+    }
+
+    /**
+     * Creates a new paragraph with the given text.
+     *
+     * @param text
+     *            the text
+     */
+    public Pre(String text) {
+        super();
+        setText(text);
+    }
+}
diff --git a/flow-html-components/src/test/java/com/vaadin/flow/component/html/PreTest.java b/flow-html-components/src/test/java/com/vaadin/flow/component/html/PreTest.java
new file mode 100644
index 00000000000..b544dada6b1
--- /dev/null
+++ b/flow-html-components/src/test/java/com/vaadin/flow/component/html/PreTest.java
@@ -0,0 +1,26 @@
+/*
+ * Copyright 2000-2018 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.flow.component.html;
+
+public class PreTest extends ComponentTest {
+    // Actual test methods in super class
+
+    @Override
+    protected void addProperties() {
+        // Component defines no new properties
+    }
+
+}
diff --git a/flow-maven-plugin/src/main/java/com/vaadin/flow/plugin/common/FlowPluginFrontendUtils.java b/flow-maven-plugin/src/main/java/com/vaadin/flow/plugin/common/FlowPluginFrontendUtils.java
index 37f8f83502e..6cf2fa8dc64 100644
--- a/flow-maven-plugin/src/main/java/com/vaadin/flow/plugin/common/FlowPluginFrontendUtils.java
+++ b/flow-maven-plugin/src/main/java/com/vaadin/flow/plugin/common/FlowPluginFrontendUtils.java
@@ -38,7 +38,7 @@ public class FlowPluginFrontendUtils {
      * Additionally include compile-time-only dependencies matching the pattern.
      */
     private static final String INCLUDE_FROM_COMPILE_DEPS_REGEX =
-            ".*(/|\\\\)portlet-api-.+jar$";
+            ".*(/|\\\\)(portlet-api|javax\\.servlet-api)-.+jar$";
 
     private FlowPluginFrontendUtils() {
     }
diff --git a/flow-maven-plugin/src/main/java/com/vaadin/flow/plugin/maven/BuildFrontendMojo.java b/flow-maven-plugin/src/main/java/com/vaadin/flow/plugin/maven/BuildFrontendMojo.java
index 087f2d22698..8016704a48e 100644
--- a/flow-maven-plugin/src/main/java/com/vaadin/flow/plugin/maven/BuildFrontendMojo.java
+++ b/flow-maven-plugin/src/main/java/com/vaadin/flow/plugin/maven/BuildFrontendMojo.java
@@ -129,6 +129,9 @@ public class BuildFrontendMojo extends FlowModeAbstractMojo {
             + Constants.LOCAL_FRONTEND_RESOURCES_PATH)
     protected File frontendResourcesDirectory;
 
+    @Parameter
+    private String polymerVersion;
+
     /**
      * Whether to use byte code scanner strategy to discover frontend
      * components.
@@ -192,7 +195,7 @@ private void runNodeUpdater() throws ExecutionFailedException {
                         .withConnectJavaSourceFolder(javaSourceFolder)
                         .withConnectGeneratedOpenApiJson(openApiJsonFile)
                         .withConnectClientTsApiFolder(generatedTsFolder)
-                        .build().execute();
+                        .withPolymerVersion(polymerVersion).build().execute();
     }
 
     private void runWebpack() {
diff --git a/flow-migration/src/test/java/com/vaadin/flow/migration/MigrationTest.java b/flow-migration/src/test/java/com/vaadin/flow/migration/MigrationTest.java
index 68b6f53d6d7..adb229ddebb 100644
--- a/flow-migration/src/test/java/com/vaadin/flow/migration/MigrationTest.java
+++ b/flow-migration/src/test/java/com/vaadin/flow/migration/MigrationTest.java
@@ -130,12 +130,12 @@ public void migratePassesHappyPath()
                 Paths.get(sourcesFolder.getPath(), "foobar").toFile());
 
         // Expected execution calls:
-        // 1 - npm install polymer-modulizer
+        // 1 - npm --no-update-notifier install polymer-modulizer
         // 2 - node {tempFolder} i -F --confid.interactive=false -S polymer#2.8.0
-        // 3 - npm i
+        // 3 - npm --no-update-notifier i
         // 4 - node node_modules/polymer-modulizer/bin/modulizer.js --force --out , --import-style=name
 
-        LinkedList excecuteExpectations = Stream.of(3, 7, 2, 6)
+        LinkedList excecuteExpectations = Stream.of(4, 7, 3, 6)
                 .collect(Collectors.toCollection(LinkedList::new));
         
         Migration migration = new Migration(configuration) {
diff --git a/flow-server/src/main/java/com/vaadin/flow/component/ClientCallable.java b/flow-server/src/main/java/com/vaadin/flow/component/ClientCallable.java
index 7d59c8174a2..d08d4794602 100644
--- a/flow-server/src/main/java/com/vaadin/flow/component/ClientCallable.java
+++ b/flow-server/src/main/java/com/vaadin/flow/component/ClientCallable.java
@@ -25,7 +25,9 @@
 
 /**
  * Publishes the annotated method so it can be invoked from the client side
- * using the notation this.$server.method() in template methods.
+ * using the notation this.$server.method(). The method will return
+ * a Promise which will be resolved with either the return value from the server
+ * or a generic rejection if the server-side method throws an exception.
  *
  * @author Vaadin Ltd
  * @since 1.0
diff --git a/flow-server/src/main/java/com/vaadin/flow/component/HasComponents.java b/flow-server/src/main/java/com/vaadin/flow/component/HasComponents.java
index c534aff8980..73d1eb6a356 100644
--- a/flow-server/src/main/java/com/vaadin/flow/component/HasComponents.java
+++ b/flow-server/src/main/java/com/vaadin/flow/component/HasComponents.java
@@ -55,10 +55,10 @@ default void add(Component... components) {
     }
 
     /**
-     * Add the given text as children of this component.
+     * Add the given text as a child of this component.
      *
      * @param text
-     *            the text to add
+     *            the text to add, not null
      */
     default void add(String text) {
         add(new Text(text));
diff --git a/flow-server/src/main/java/com/vaadin/flow/component/Text.java b/flow-server/src/main/java/com/vaadin/flow/component/Text.java
index 9b65f919c32..f9481fcd1e4 100644
--- a/flow-server/src/main/java/com/vaadin/flow/component/Text.java
+++ b/flow-server/src/main/java/com/vaadin/flow/component/Text.java
@@ -29,7 +29,7 @@ public class Text extends Component implements HasText {
      * Creates an instance using the given text.
      *
      * @param text
-     *            the text to show
+     *            the text to show, not null
      */
     public Text(String text) {
         super(Element.createText(text));
diff --git a/flow-server/src/main/java/com/vaadin/flow/component/page/Page.java b/flow-server/src/main/java/com/vaadin/flow/component/page/Page.java
index 997e39943dc..b9c75d80fab 100644
--- a/flow-server/src/main/java/com/vaadin/flow/component/page/Page.java
+++ b/flow-server/src/main/java/com/vaadin/flow/component/page/Page.java
@@ -414,9 +414,9 @@ public ExecutionCanceler executeJavaScript(String expression,
     /**
      * Asynchronously runs the given JavaScript expression in the browser.
      * 

-     * It is possible to get access to the return value of the execution by
-     * registering a handler with the returned pending result. If no handler is
-     * registered, the return value will be ignored.
+     * The returned PendingJavaScriptResult can be used to retrieve
+     * any return value from the JavaScript expression. If no
+     * return value handler is registered, the return value will be ignored.
      * 

      * The given parameters will be available to the expression as variables
      * named $0, $1, and so on. Supported parameter
@@ -550,7 +550,7 @@ public void open(String url) {
      * @param windowName
      *            the name of the window.
      */
-    private void open(String url, String windowName) {
+    public void open(String url, String windowName) {
         executeJavaScript("window.open($0, $1)", url, windowName);
     }
 
diff --git a/flow-server/src/main/java/com/vaadin/flow/component/polymertemplate/BundleParser.java b/flow-server/src/main/java/com/vaadin/flow/component/polymertemplate/BundleParser.java
index 58cb21abb0b..a145e7e6d78 100644
--- a/flow-server/src/main/java/com/vaadin/flow/component/polymertemplate/BundleParser.java
+++ b/flow-server/src/main/java/com/vaadin/flow/component/polymertemplate/BundleParser.java
@@ -15,12 +15,14 @@
  */
 package com.vaadin.flow.component.polymertemplate;
 
+import java.util.Optional;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
 import org.jsoup.Jsoup;
 import org.jsoup.nodes.Document;
 import org.jsoup.nodes.Element;
+import org.jsoup.select.Elements;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -30,6 +32,7 @@
 import elemental.json.JsonArray;
 import elemental.json.JsonObject;
 import elemental.json.JsonType;
+
 import static elemental.json.JsonType.ARRAY;
 import static elemental.json.JsonType.OBJECT;
 import static elemental.json.JsonType.STRING;
@@ -79,13 +82,19 @@ public final class BundleParser {
      * end character with ;} e.g. ';}
      */
     private static final Pattern TEMPLATE_PATTERN = Pattern.compile(
-            "get[\\s]*template\\(\\)[\\s]*\\{[\\s]*return[\\s]*html([\\`|\\'|\\\"])([\\s\\S]*)\\1;[\\s]*\\}");
+            "get[\\s]*template\\(\\)[\\s]*\\{[\\s]*return[\\s]*html([\\`\\'\\\"])([\\s\\S]*)\\1;[\\s]*\\}");
+
+    private static final Pattern NO_TEMPLATE_PATTERN = Pattern.compile(
+            "innerHTML[\\s]*=[\\s]*([\\`\\'\\\"])([\\s]* !node.equals(templateDocument.body()))
+                .filter(node -> !node.equals(body))
                 .forEach(template::appendChild);
 
         return template;
     }
 
+    private static Element tryParsePolymer2(Document templateDocument,
+            Matcher noTemplateMatcher) {
+        while (noTemplateMatcher.find()
+                && noTemplateMatcher.groupCount() == 2) {
+            String group = noTemplateMatcher.group(2);
+            LOGGER.trace(
+                    "Found Polymer 2 style insertion as a Polymer 3 template content {}",
+                    group);
+
+            templateDocument = Jsoup.parse(group);
+            LOGGER.trace("The parsed template document was {}",
+                    templateDocument);
+            Optional domModule = JsoupUtils
+                    .getDomModule(templateDocument, null);
+            if (!domModule.isPresent()) {
+                continue;
+            }
+            JsoupUtils.removeCommentsRecursively(domModule.get());
+            Elements templates = domModule.get()
+                    .getElementsByTag(TEMPLATE_TAG_NAME);
+            if (templates.isEmpty()) {
+                continue;
+            }
+            return templates.get(0);
+        }
+        return null;
+    }
+
     // From the statistics json recursively go through all chunks and modules to
     // find the first module whose name matches the file name
     private static String getSourceFromObject(JsonObject module,
@@ -211,10 +259,11 @@ && validKey(module, SOURCE, STRING)) {
                     .replaceFirst("^frontend://", ".");
 
             // For polymer templates inside add-ons we will not find the sources
-            // using ./ as the actual path contains "node_modules/@vaadin/flow-frontend/" instead of "./"
+            // using ./ as the actual path contains
+            // "node_modules/@vaadin/flow-frontend/" instead of "./"
             if (name.contains(FrontendUtils.FLOW_NPM_PACKAGE_NAME)) {
-                alternativeFileName = alternativeFileName
-                        .replaceFirst("\\./", "");
+                alternativeFileName = alternativeFileName.replaceFirst("\\./",
+                        "");
             }
 
             // Remove query-string used by webpack modules like babel (e.g
@@ -247,4 +296,18 @@ private static boolean validKey(JsonObject o, String k, JsonType t) {
                 && o.get(k).getType().equals(t);
         return validKey && (!t.equals(STRING) || !o.getString(k).isEmpty());
     }
+
+    /**
+     * Removes comments (block comments and line comments) from the JS code.
+     * 

+     * Note that this is not really a correct way to do this: this will remove
+     * comments also if they are inside strings. But this is not important here
+     * in this class since we care only about import statements where this is
+     * fine.
+     *
+     * @return the code with removed comments
+     */
+    private static String removeComments(String content) {
+        return COMMENTS_PATTERN.matcher(content).replaceAll("");
+    }
 }
diff --git a/flow-server/src/main/java/com/vaadin/flow/component/polymertemplate/DefaultTemplateParser.java b/flow-server/src/main/java/com/vaadin/flow/component/polymertemplate/DefaultTemplateParser.java
index 8b95566188e..d94314a7554 100644
--- a/flow-server/src/main/java/com/vaadin/flow/component/polymertemplate/DefaultTemplateParser.java
+++ b/flow-server/src/main/java/com/vaadin/flow/component/polymertemplate/DefaultTemplateParser.java
@@ -25,10 +25,8 @@
 import java.util.stream.Collectors;
 
 import org.jsoup.Jsoup;
-import org.jsoup.nodes.Comment;
 import org.jsoup.nodes.Document;
 import org.jsoup.nodes.Element;
-import org.jsoup.nodes.Node;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -141,13 +139,13 @@ private static Element parseHtmlImport(InputStream content, String path,
         try {
             Document parsedDocument = Jsoup.parse(content,
                     StandardCharsets.UTF_8.name(), "");
-            Optional optionalDomModule = getDomModule(parsedDocument,
-                    tag);
+            Optional optionalDomModule = JsoupUtils
+                    .getDomModule(parsedDocument, tag);
             if (!optionalDomModule.isPresent()) {
                 return null;
             }
             Element domModule = optionalDomModule.get();
-            removeCommentsRecursively(domModule);
+            JsoupUtils.removeCommentsRecursively(domModule);
             return domModule;
         } catch (IOException exception) {
             throw new RuntimeException(String.format(
@@ -156,24 +154,6 @@ private static Element parseHtmlImport(InputStream content, String path,
         }
     }
 
-    private static Optional getDomModule(Element parent, String id) {
-        return parent.getElementsByTag("dom-module").stream()
-                .filter(element -> id.equals(element.id())).findFirst();
-    }
-
-    private static void removeCommentsRecursively(Node node) {
-        int i = 0;
-        while (i < node.childNodeSize()) {
-            Node child = node.childNode(i);
-            if (child instanceof Comment) {
-                child.remove();
-            } else {
-                removeCommentsRecursively(child);
-                i++;
-            }
-        }
-    }
-
     private Logger getLogger() {
         return LoggerFactory.getLogger(DefaultTemplateParser.class.getName());
     }
diff --git a/flow-server/src/main/java/com/vaadin/flow/component/polymertemplate/IdMapper.java b/flow-server/src/main/java/com/vaadin/flow/component/polymertemplate/IdMapper.java
index 17c77873e8e..43b3add8540 100644
--- a/flow-server/src/main/java/com/vaadin/flow/component/polymertemplate/IdMapper.java
+++ b/flow-server/src/main/java/com/vaadin/flow/component/polymertemplate/IdMapper.java
@@ -20,7 +20,6 @@
 import java.util.HashMap;
 import java.util.Optional;
 import java.util.function.Consumer;
-import java.util.stream.Stream;
 
 import com.vaadin.flow.component.Component;
 import com.vaadin.flow.component.Tag;
@@ -74,25 +73,7 @@ public IdMapper(AbstractTemplate template) {
      */
     public void mapComponentOrElement(Field field, String id, String tag,
             Consumer beforeComponentInject) {
-        Element element = getElementById(id).orElse(null);
-
-        if (element == null) {
-            injectClientSideElement(tag, id, field, beforeComponentInject);
-        } else {
-            injectServerSideElement(element, field, beforeComponentInject);
-        }
-    }
-
-    private void injectServerSideElement(Element element, Field field,
-            Consumer beforeComponentInject) {
-        if (getElement().equals(element)) {
-            throw new IllegalArgumentException(
-                    "Cannot map the root element of the template. "
-                            + "This is always mapped to the template instance itself ("
-                            + getContainerClass().getName() + ')');
-        } else if (element != null) {
-            injectTemplateElement(element, field, beforeComponentInject);
-        }
+        injectClientSideElement(tag, id, field, beforeComponentInject);
     }
 
     private Class getContainerClass() {
@@ -132,20 +113,6 @@ private Element getElement() {
         return template.getElement();
     }
 
-    private Optional getElementById(String id) {
-        return getOrCreateShadowRoot().getChildren()
-                .flatMap(this::flattenChildren)
-                .filter(element -> id.equals(element.getAttribute("id")))
-                .findFirst();
-    }
-
-    private Stream flattenChildren(Element node) {
-        if (node.getChildCount() > 0) {
-            return node.getChildren().flatMap(this::flattenChildren);
-        }
-        return Stream.of(node);
-    }
-
     /**
      * Attaches a child element with the given {@code tagName} and {@code id} to
      * an existing dom element on the client side with matching data.
diff --git a/flow-server/src/main/java/com/vaadin/flow/component/polymertemplate/JsoupUtils.java b/flow-server/src/main/java/com/vaadin/flow/component/polymertemplate/JsoupUtils.java
new file mode 100644
index 00000000000..1ae6456be56
--- /dev/null
+++ b/flow-server/src/main/java/com/vaadin/flow/component/polymertemplate/JsoupUtils.java
@@ -0,0 +1,77 @@
+/*
+ * Copyright 2000-2018 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.flow.component.polymertemplate;
+
+import java.util.Optional;
+import java.util.stream.Stream;
+
+import org.jsoup.nodes.Comment;
+import org.jsoup.nodes.Element;
+import org.jsoup.nodes.Node;
+
+/**
+ * Utilities for JSOUP DOM manipulations.
+ *
+ * @author Vaadin Ltd
+ *
+ */
+final class JsoupUtils {
+
+    private JsoupUtils() {
+        // Utility class
+    }
+
+    /**
+     * Removes all comments from the {@code node} tree.
+     *
+     * @param node
+     *            a Jsoup node
+     */
+    static void removeCommentsRecursively(Node node) {
+        int i = 0;
+        while (i < node.childNodeSize()) {
+            Node child = node.childNode(i);
+            if (child instanceof Comment) {
+                child.remove();
+            } else {
+                removeCommentsRecursively(child);
+                i++;
+            }
+        }
+    }
+
+    /**
+     * Finds {@code "dom-module"} element inside the {@code parent}.
+     * 

+     * If {@code id} is provided then {@code "dom-module"} element is searched
+     * with the given {@code id} value.
+     *
+     * @param parent
+     *            the parent element
+     * @param id
+     *            optional id attribute value to search {@code "dom-module"}
+     *            element, may be {@code null}
+     * @return
+     */
+    static Optional getDomModule(Element parent, String id) {
+        Stream stream = parent.getElementsByTag("dom-module").stream();
+        if (id != null) {
+            stream = stream.filter(element -> id.equals(element.id()));
+        }
+        return stream.findFirst();
+    }
+
+}
diff --git a/flow-server/src/main/java/com/vaadin/flow/component/polymertemplate/NpmTemplateParser.java b/flow-server/src/main/java/com/vaadin/flow/component/polymertemplate/NpmTemplateParser.java
index ca3e490fa4a..ebda6011976 100644
--- a/flow-server/src/main/java/com/vaadin/flow/component/polymertemplate/NpmTemplateParser.java
+++ b/flow-server/src/main/java/com/vaadin/flow/component/polymertemplate/NpmTemplateParser.java
@@ -122,14 +122,16 @@ public TemplateData getTemplateContent(
         }
 
         if (chosenDep != null) {
-            // Template needs to be wrapped in an element with id, to look
-            // like a P2 template
-            Element parent = new Element(tag);
-            parent.attr("id", tag);
 
             Element templateElement = BundleParser.parseTemplateElement(
                     chosenDep.getFirst().getUrl(), chosenDep.getSecond());
-            templateElement.appendTo(parent);
+            if (!JsoupUtils.getDomModule(templateElement, null).isPresent()) {
+                // Template needs to be wrapped in an element with id, to look
+                // like a P2 template
+                Element parent = new Element(tag);
+                parent.attr("id", tag);
+                templateElement.appendTo(parent);
+            }
 
             return new TemplateData(chosenDep.getFirst().getUrl(),
                     templateElement);
diff --git a/flow-server/src/main/java/com/vaadin/flow/component/polymertemplate/TemplateInitializer.java b/flow-server/src/main/java/com/vaadin/flow/component/polymertemplate/TemplateInitializer.java
index d4ec693db02..6e222b1d1b8 100644
--- a/flow-server/src/main/java/com/vaadin/flow/component/polymertemplate/TemplateInitializer.java
+++ b/flow-server/src/main/java/com/vaadin/flow/component/polymertemplate/TemplateInitializer.java
@@ -116,8 +116,6 @@ private void doRequestAttachCustomElement(String id, String tag,
         if (idMapper.isMapped(id)) {
             return;
         }
-        // make sure that shadow root is available
-        idMapper.getOrCreateShadowRoot();
 
         Element element = new Element(tag);
         VirtualChildrenList list = getElement().getNode()
diff --git a/flow-server/src/main/java/com/vaadin/flow/component/webcomponent/WebComponentWrapper.java b/flow-server/src/main/java/com/vaadin/flow/component/webcomponent/WebComponentWrapper.java
index b5e4698aaa7..5fad098d6e9 100644
--- a/flow-server/src/main/java/com/vaadin/flow/component/webcomponent/WebComponentWrapper.java
+++ b/flow-server/src/main/java/com/vaadin/flow/component/webcomponent/WebComponentWrapper.java
@@ -119,7 +119,8 @@ public void disconnected() {
                         if (event.getSource().getInternals()
                                 .getLastHeartbeatTimestamp()
                                 - disconnect > timeout) {
-                            this.getElement().removeFromParent();
+                            Element element = this.getElement();
+                            element.getParent().removeVirtualChild(element);
                         }
                     });
         }
diff --git a/flow-server/src/main/java/com/vaadin/flow/dom/Element.java b/flow-server/src/main/java/com/vaadin/flow/dom/Element.java
index 2095be41423..132f4a24647 100644
--- a/flow-server/src/main/java/com/vaadin/flow/dom/Element.java
+++ b/flow-server/src/main/java/com/vaadin/flow/dom/Element.java
@@ -220,7 +220,7 @@ public Stream getChildren() {
      * Creates a text node with the given text.
      *
      * @param text
-     *            the text in the node
+     *            the text in the node, not null
      * @return an element representing the text node
      */
     public static Element createText(String text) {
@@ -1669,9 +1669,10 @@ public void executeJavaScript(String expression,
     // When updating JavaDocs here, keep in sync with Page.executeJavaScript
     /**
      * Asynchronously runs the given JavaScript expression in the browser in the
-     * context of this element. It is possible to get access to the return value
-     * of the execution by registering a handler with the returned pending
-     * result. If no handler is registered, the return value will be ignored.
+     * context of this element. The returned
+     * PendingJavaScriptResult can be used to retrieve any
+     * return value from the JavaScript expression. If no return
+     * value handler is registered, the return value will be ignored.
      * 

      * This element will be available to the expression as this.
      * The given parameters will be available as variables named
diff --git a/flow-server/src/main/java/com/vaadin/flow/dom/Node.java b/flow-server/src/main/java/com/vaadin/flow/dom/Node.java
index 4fdf1f3b44b..366358ab85c 100644
--- a/flow-server/src/main/java/com/vaadin/flow/dom/Node.java
+++ b/flow-server/src/main/java/com/vaadin/flow/dom/Node.java
@@ -180,6 +180,50 @@ public N appendVirtualChild(Element... children) {
         return getSelf();
     }
 
+    /**
+     * Removes the given children that have been attached as the virtual
+     * children of this element.
+     * 

+     * The virtual child is not really a child of the DOM element. The
+     * client-side counterpart is created in the memory but it's not attached to
+     * the DOM tree. The resulting element is referenced via the server side
+     * {@link Element} in JS function call as usual. *
+     * 
+     * @param children
+     *            the element(s) to remove
+     * @return this element
+     */
+    /*
+     * The use case for removing virtual children is when exported Flow web
+     * components are detached from their parent due to missing heart beats +
+     * timeout.
+     */
+    public N removeVirtualChild(Element... children) {
+        if (children == null) {
+            throw new IllegalArgumentException(
+                    THE_CHILDREN_ARRAY_CANNOT_BE_NULL);
+        }
+
+        if (getNode().hasFeature(VirtualChildrenList.class)) {
+            VirtualChildrenList childrenList = getNode()
+                    .getFeature(VirtualChildrenList.class);
+            for (Element child : children) {
+                if (child == null) {
+                    throw new IllegalArgumentException(
+                            "Element to remove must not be null");
+                }
+                int index = childrenList.indexOf(child.getNode());
+                if (index == -1) {
+                    throw new IllegalArgumentException(
+                            "Trying to detach a virtual child element from parent that does not have it.");
+                }
+                childrenList.remove(index);
+            }
+        }
+
+        return getSelf();
+    }
+
     /**
      * Gets whether this element is a virtual child of its parent.
      *
diff --git a/flow-server/src/main/java/com/vaadin/flow/dom/impl/AbstractNodeStateProvider.java b/flow-server/src/main/java/com/vaadin/flow/dom/impl/AbstractNodeStateProvider.java
index ffba5ec92c7..d2171d6cbf9 100644
--- a/flow-server/src/main/java/com/vaadin/flow/dom/impl/AbstractNodeStateProvider.java
+++ b/flow-server/src/main/java/com/vaadin/flow/dom/impl/AbstractNodeStateProvider.java
@@ -120,10 +120,9 @@ public void removeChild(StateNode node, Element child) {
         ElementChildrenList childrenFeature = getChildrenFeature(node);
         int pos = childrenFeature.indexOf(child.getNode());
         if (pos == -1) {
-            throw new IllegalArgumentException("Not in the list");
+            throw new IllegalArgumentException("Trying to detach an element from parent that does not have it.");
         }
         childrenFeature.remove(pos);
-
     }
 
     @Override
diff --git a/flow-server/src/main/java/com/vaadin/flow/dom/impl/BasicTextElementStateProvider.java b/flow-server/src/main/java/com/vaadin/flow/dom/impl/BasicTextElementStateProvider.java
index 1ba8a83b968..2cb208186c1 100644
--- a/flow-server/src/main/java/com/vaadin/flow/dom/impl/BasicTextElementStateProvider.java
+++ b/flow-server/src/main/java/com/vaadin/flow/dom/impl/BasicTextElementStateProvider.java
@@ -42,7 +42,7 @@ private BasicTextElementStateProvider() {
      * Creates a compatible text state node using the given text.
      *
      * @param text
-     *            the text to use
+     *            the text to use, not null
      * @return a initialized and compatible state node
      */
     public static StateNode createStateNode(String text) {
diff --git a/flow-server/src/main/java/com/vaadin/flow/function/DeploymentConfiguration.java b/flow-server/src/main/java/com/vaadin/flow/function/DeploymentConfiguration.java
index 14409ed7441..fbcc296817a 100644
--- a/flow-server/src/main/java/com/vaadin/flow/function/DeploymentConfiguration.java
+++ b/flow-server/src/main/java/com/vaadin/flow/function/DeploymentConfiguration.java
@@ -129,8 +129,8 @@ default boolean isClientSideMode() {
     boolean isSendUrlsAsParameters();
 
     /**
-     * Returns whether a session should be closed when all its open UIs have
-     * been idle for longer than its configured maximum inactivity time.
+     * Returns whether a Vaadin session should be closed when all its open UIs
+     * have been idle for longer than its configured maximum inactivity time.
      * 

      * A UI is idle if it is open on the client side but has no activity other
      * than heartbeat requests. If {@code isCloseIdleSessions() == false},
@@ -141,8 +141,8 @@ default boolean isClientSideMode() {
      * @see WrappedSession#getMaxInactiveInterval()
      *
      *
-     * @return True if UIs and sessions receiving only heartbeat requests are
-     *         eventually closed; false if heartbeat requests extend UI and
+     * @return True if UIs and Vaadin sessions receiving only heartbeat requests
+     *         are eventually closed; false if heartbeat requests extend UI and
      *         session lifetime indefinitely.
      */
     boolean isCloseIdleSessions();
@@ -395,20 +395,41 @@ default List getPolyfills() {
      * @return true if dev server should be used
      */
     default boolean enableDevServer() {
-        return getBooleanProperty(
-                Constants.SERVLET_PARAMETER_ENABLE_DEV_SERVER, true);
+        return getBooleanProperty(Constants.SERVLET_PARAMETER_ENABLE_DEV_SERVER,
+                true);
     }
 
     /**
-     * Get if the dev server should be reused on each reload.
-     * True by default, set it to false in tests so as dev server
-     * is not kept as a daemon after the test.
+     * Get if the dev server should be reused on each reload. True by default,
+     * set it to false in tests so as dev server is not kept as a daemon after
+     * the test.
      *
      * @return true if dev server should be reused
      */
     default boolean reuseDevServer() {
-        return getBooleanProperty(
-                Constants.SERVLET_PARAMETER_REUSE_DEV_SERVER, true);
+        return getBooleanProperty(Constants.SERVLET_PARAMETER_REUSE_DEV_SERVER,
+                true);
+    }
+
+    /**
+     * Get if the stats.json file should be retrieved from an external service or
+     * through the classpath.
+     *
+     * @return true if stats.json is served from an external location
+     */
+    default boolean isStatsExternal() {
+        return getBooleanProperty(Constants.EXTERNAL_STATS_FILE, false);
+    }
+
+    /**
+     * Get the url from where stats.json should be retrieved from.
+     * If not given this will default to '/vaadin-static/VAADIN/config/stats.json'
+     *
+     * @return external stats.json location
+     */
+    default String getExternalStatsUrl() {
+        return getStringProperty(Constants.EXTERNAL_STATS_URL,
+                Constants.DEFAULT_EXTERNAL_STATS_URL);
     }
 
     /**
diff --git a/flow-server/src/main/java/com/vaadin/flow/internal/JsonCodec.java b/flow-server/src/main/java/com/vaadin/flow/internal/JsonCodec.java
index 2d841c168b1..5e9cfe3b871 100644
--- a/flow-server/src/main/java/com/vaadin/flow/internal/JsonCodec.java
+++ b/flow-server/src/main/java/com/vaadin/flow/internal/JsonCodec.java
@@ -80,6 +80,8 @@ private JsonCodec() {
      * @return the value encoded as JSON
      */
     public static JsonValue encodeWithTypeInfo(Object value) {
+        assert value == null || canEncodeWithTypeInfo(value.getClass());
+
         if (value instanceof Component) {
             return encodeNode(((Component) value).getElement());
         } else if (value instanceof Node) {
@@ -119,7 +121,7 @@ private static JsonArray wrapComplexValue(int typeId, JsonValue... values) {
 
     /**
      * Helper for checking whether the type is supported by
-     * {@link #encodeWithoutTypeInfo(Object)}. Supported values types are
+     * {@link #encodeWithoutTypeInfo(Object)}. Supported value types are
      * {@link String}, {@link Integer}, {@link Double}, {@link Boolean},
      * {@link JsonValue}.
      *
@@ -134,6 +136,23 @@ public static boolean canEncodeWithoutTypeInfo(Class type) {
                 || JsonValue.class.isAssignableFrom(type);
     }
 
+    /**
+     * Helper for checking whether the type is supported by
+     * {@link #encodeWithTypeInfo(Object)}. Supported values types are
+     * {@link Node}, {@link Component}, {@link ReturnChannelRegistration} and
+     * anything accepted by {@link #canEncodeWithoutTypeInfo(Class)}.
+     *
+     * @param type
+     *            the type to check
+     * @return whether the type can be encoded
+     */
+    public static boolean canEncodeWithTypeInfo(Class type) {
+        return canEncodeWithoutTypeInfo(type)
+                || Node.class.isAssignableFrom(type)
+                || Component.class.isAssignableFrom(type)
+                || ReturnChannelRegistration.class.isAssignableFrom(type);
+    }
+
     /**
      * Encodes a "primitive" value or a constant pool reference to JSON. This
      * methods supports {@link ConstantPoolKey} in addition to the types
@@ -168,6 +187,9 @@ public static JsonValue encodeWithoutTypeInfo(Object value) {
         if (value == null) {
             return Json.createNull();
         }
+
+        assert canEncodeWithoutTypeInfo(value.getClass());
+
         Class type = value.getClass();
         if (String.class.equals(value.getClass())) {
             return Json.create((String) value);
diff --git a/flow-server/src/main/java/com/vaadin/flow/internal/nodefeature/AbstractServerHandlers.java b/flow-server/src/main/java/com/vaadin/flow/internal/nodefeature/AbstractServerHandlers.java
index 023a66a800f..48a277cdedb 100644
--- a/flow-server/src/main/java/com/vaadin/flow/internal/nodefeature/AbstractServerHandlers.java
+++ b/flow-server/src/main/java/com/vaadin/flow/internal/nodefeature/AbstractServerHandlers.java
@@ -166,15 +166,7 @@ protected void collectHandlerMethods(Class clazz,
      */
     protected void addHandlerMethod(Method method, Collection methods) {
         ensureSupportedParameterTypes(method);
-        if (!void.class.equals(method.getReturnType())) {
-            String msg = String.format(Locale.ENGLISH,
-                    "Only void handler methods are supported. "
-                            + "Component '%s' has method '%s' annotated with '%s' whose return type is not void but %s",
-                    method.getDeclaringClass().getName(), method.getName(),
-                    getHandlerAnnotation().getName(),
-                    method.getReturnType().getSimpleName());
-            throw new IllegalStateException(msg);
-        }
+        ensureSupportedReturnType(method);
         Optional> checkedException = Stream
                 .of(method.getExceptionTypes())
                 .filter(ReflectTools::isCheckedException).findFirst();
@@ -191,6 +183,24 @@ protected void addHandlerMethod(Method method, Collection methods) {
         methods.add(method);
     }
 
+    /**
+     * Validate return type support for given method.
+     *
+     * @param method
+     *            method to check return type for
+     */
+    protected void ensureSupportedReturnType(Method method) {
+        if (!void.class.equals(method.getReturnType())) {
+            String msg = String.format(Locale.ENGLISH,
+                    "Only void handler methods are supported. "
+                            + "Component '%s' has method '%s' annotated with '%s' whose return type is not void but \"%s\"",
+                    method.getDeclaringClass().getName(), method.getName(),
+                    getHandlerAnnotation().getName(),
+                    method.getReturnType().getSimpleName());
+            throw new IllegalStateException(msg);
+        }
+    }
+
     /**
      * Gets the annotation which is used to mark methods as handlers.
      *
diff --git a/flow-server/src/main/java/com/vaadin/flow/internal/nodefeature/ClientCallableHandlers.java b/flow-server/src/main/java/com/vaadin/flow/internal/nodefeature/ClientCallableHandlers.java
index c96f14c51bc..d34ae0a4368 100644
--- a/flow-server/src/main/java/com/vaadin/flow/internal/nodefeature/ClientCallableHandlers.java
+++ b/flow-server/src/main/java/com/vaadin/flow/internal/nodefeature/ClientCallableHandlers.java
@@ -16,10 +16,13 @@
 package com.vaadin.flow.internal.nodefeature;
 
 import java.lang.reflect.Method;
+import java.util.Locale;
 
 import com.vaadin.flow.component.ClientCallable;
 import com.vaadin.flow.component.Component;
 import com.vaadin.flow.dom.DisabledUpdateMode;
+import com.vaadin.flow.internal.JsonCodec;
+import com.vaadin.flow.internal.ReflectTools;
 import com.vaadin.flow.internal.StateNode;
 
 /**
@@ -53,6 +56,25 @@ protected void ensureSupportedParameterTypes(Method method) {
         // limit supported types
     }
 
+    @Override
+    protected void ensureSupportedReturnType(Method method) {
+        Class returnType = method.getReturnType();
+        if (returnType.isPrimitive()) {
+            returnType = ReflectTools.convertPrimitiveType(returnType);
+        }
+
+        if (!void.class.equals(returnType)
+                && !JsonCodec.canEncodeWithTypeInfo(returnType)) {
+            String msg = String.format(Locale.ENGLISH,
+                    "Only return types that can be used as Element.executeJs parameters are supported. "
+                            + "Component '%s' has method '%s' annotated with '%s' whose return type is \"%s\"",
+                    method.getDeclaringClass().getName(), method.getName(),
+                    getHandlerAnnotation().getName(),
+                    method.getReturnType().getSimpleName());
+            throw new IllegalStateException(msg);
+        }
+    }
+
     @Override
     protected DisabledUpdateMode getUpdateMode(Method method) {
         return method.getAnnotation(getHandlerAnnotation()).value();
diff --git a/flow-server/src/main/java/com/vaadin/flow/internal/nodefeature/TextNodeMap.java b/flow-server/src/main/java/com/vaadin/flow/internal/nodefeature/TextNodeMap.java
index 673035ace75..9539f4273b8 100644
--- a/flow-server/src/main/java/com/vaadin/flow/internal/nodefeature/TextNodeMap.java
+++ b/flow-server/src/main/java/com/vaadin/flow/internal/nodefeature/TextNodeMap.java
@@ -44,7 +44,7 @@ protected String getKey() {
      * Sets the text of this node.
      *
      * @param text
-     *            the text, not null
+     *            the text, not null
      */
     public void setText(String text) {
         assert text != null;
diff --git a/flow-server/src/main/java/com/vaadin/flow/internal/nodefeature/VirtualChildrenList.java b/flow-server/src/main/java/com/vaadin/flow/internal/nodefeature/VirtualChildrenList.java
index 619140944f3..2aa0a10961e 100644
--- a/flow-server/src/main/java/com/vaadin/flow/internal/nodefeature/VirtualChildrenList.java
+++ b/flow-server/src/main/java/com/vaadin/flow/internal/nodefeature/VirtualChildrenList.java
@@ -154,8 +154,17 @@ public Iterator iterator() {
     }
 
     @Override
-    protected StateNode remove(int index) {
-        throw new UnsupportedOperationException();
+    public int indexOf(StateNode node) {
+        return super.indexOf(node);
+    }
+
+    @Override
+    public StateNode remove(int index) {
+        // removing the payload in case the element is reused
+        get(index).getFeature(ElementData.class).remove(NodeProperties.PAYLOAD);
+
+        // this should not omit a node change to client side.
+        return super.remove(index);
     }
 
     @Override
diff --git a/flow-server/src/main/java/com/vaadin/flow/router/RouterLink.java b/flow-server/src/main/java/com/vaadin/flow/router/RouterLink.java
index 3d2e144376e..aa08009674b 100644
--- a/flow-server/src/main/java/com/vaadin/flow/router/RouterLink.java
+++ b/flow-server/src/main/java/com/vaadin/flow/router/RouterLink.java
@@ -183,6 +183,39 @@ public > void setRoute(
         updateHref(url);
     }
 
+    /**
+     * Set the navigation target for this link.
+     *
+     * @param navigationTarget
+     *         navigation target
+     */
+    public void setRoute(Class navigationTarget) {
+        validateRouteParameters(getRouter(), navigationTarget);
+        String url = RouteConfiguration.forRegistry(getRouter().getRegistry())
+                .getUrl(navigationTarget);
+        updateHref(url);
+    }
+
+    /**
+     * Set the navigation target for this link.
+     *
+     * @param navigationTarget
+     *         navigation target
+     * @param parameter
+     *         url parameter for navigation target
+     * @param 
+     *         url parameter type
+     * @param 
+     *         navigation target type
+     */
+    public > void setRoute(
+            Class navigationTarget, T parameter) {
+        validateRouteParameters(getRouter(), navigationTarget);
+        String url = RouteConfiguration.forRegistry(getRouter().getRegistry())
+                .getUrl(navigationTarget, parameter);
+        updateHref(url);
+    }
+
     private void validateRouteParameters(Router router,
             Class navigationTarget) {
         if (router == null) {
diff --git a/flow-server/src/main/java/com/vaadin/flow/server/Constants.java b/flow-server/src/main/java/com/vaadin/flow/server/Constants.java
index f947316e00b..45509751120 100644
--- a/flow-server/src/main/java/com/vaadin/flow/server/Constants.java
+++ b/flow-server/src/main/java/com/vaadin/flow/server/Constants.java
@@ -44,6 +44,8 @@ public final class Constants implements Serializable {
     public static final String CONNECT_APPLICATION_PROPERTIES_TOKEN = "connect.applicationProperties";
     public static final String CONNECT_OPEN_API_FILE_TOKEN = "connect.openApiFile";
     public static final String CONNECT_GENERATED_TS_DIR_TOKEN = "connect.generated";
+    public static final String EXTERNAL_STATS_FILE_TOKEN = "externalStatsFile";
+    public static final String EXTERNAL_STATS_URL_TOKEN = "externalStatsUrl";
 
     /**
      * enable it if your project is a Polymer 2.0 one, should be removed in V15
@@ -217,11 +219,15 @@ public final class Constants implements Serializable {
 
     /**
      * Boolean parameter for enabling/disabling bytecode scanning in dev mode.
-     * If enabled, entry points are scanned for reachable frontend resources.
-     * If disabled, all classes on the classpath are scanned.
+     * If enabled, entry points are scanned for reachable frontend resources. If
+     * disabled, all classes on the classpath are scanned.
      */
     public static final String SERVLET_PARAMETER_DEVMODE_OPTIMIZE_BUNDLE = "devmode.optimizeBundle";
 
+    /**
+     * Configuration parameter name for polymer version.
+     */
+    public static final String SERVLET_PARAMETER_DEVMODE_POLYMER_VERSION = "devmode.polymer.version";
 
     /**
      * The path used in the vaadin servlet for handling static resources.
@@ -270,6 +276,20 @@ public final class Constants implements Serializable {
     public static final int SHOULD_WORK_NPM_MAJOR_VERSION = 5;
     public static final int SHOULD_WORK_NPM_MINOR_VERSION = 5;
 
+    /**
+     * Property boolean for marking stats.json to be fetched from external
+     * location.
+     */
+    public static final String EXTERNAL_STATS_FILE = "external.stats.file";
+    /**
+     * Property String for external stats.json location url.
+     */
+    public static final String EXTERNAL_STATS_URL = "external.stats.url";
+    /**
+     * Default location to look for the external stats.json.
+     */
+    public static final String DEFAULT_EXTERNAL_STATS_URL = "/vaadin-static/VAADIN/config/stats.json";
+
     private Constants() {
         // prevent instantiation constants class only
     }
diff --git a/flow-server/src/main/java/com/vaadin/flow/server/DeploymentConfigurationFactory.java b/flow-server/src/main/java/com/vaadin/flow/server/DeploymentConfigurationFactory.java
index a733414c6b0..f6f6bcea211 100644
--- a/flow-server/src/main/java/com/vaadin/flow/server/DeploymentConfigurationFactory.java
+++ b/flow-server/src/main/java/com/vaadin/flow/server/DeploymentConfigurationFactory.java
@@ -16,13 +16,11 @@
 
 package com.vaadin.flow.server;
 
-import javax.servlet.ServletConfig;
-import javax.servlet.ServletContext;
-import javax.servlet.ServletException;
 import java.io.File;
 import java.io.IOException;
 import java.io.Serializable;
 import java.io.UncheckedIOException;
+import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.net.URL;
 import java.nio.charset.StandardCharsets;
@@ -49,6 +47,10 @@
 import static com.vaadin.flow.server.Constants.CONNECT_GENERATED_TS_DIR_TOKEN;
 import static com.vaadin.flow.server.Constants.CONNECT_JAVA_SOURCE_FOLDER_TOKEN;
 import static com.vaadin.flow.server.Constants.CONNECT_OPEN_API_FILE_TOKEN;
+import static com.vaadin.flow.server.Constants.EXTERNAL_STATS_FILE;
+import static com.vaadin.flow.server.Constants.EXTERNAL_STATS_FILE_TOKEN;
+import static com.vaadin.flow.server.Constants.EXTERNAL_STATS_URL;
+import static com.vaadin.flow.server.Constants.EXTERNAL_STATS_URL_TOKEN;
 import static com.vaadin.flow.server.Constants.FRONTEND_TOKEN;
 import static com.vaadin.flow.server.Constants.NPM_TOKEN;
 import static com.vaadin.flow.server.Constants.SERVLET_PARAMETER_CLIENT_SIDE_MODE;
@@ -102,18 +104,16 @@ private DeploymentConfigurationFactory() {
      *
      * @param systemPropertyBaseClass
      *            the class to look for properties defined with annotations
-     * @param servletConfig
+     * @param vaadinConfig
      *            the config to get the rest of the properties from
      * @return {@link DeploymentConfiguration} instance
-     * @throws ServletException
-     *             if construction of the {@link Properties} for the parameters
-     *             fails
+     * @throws VaadinConfigurationException thrown if property construction fails
      */
     public static DeploymentConfiguration createDeploymentConfiguration(
-            Class systemPropertyBaseClass, ServletConfig servletConfig)
-            throws ServletException {
+            Class systemPropertyBaseClass, VaadinConfig vaadinConfig)
+            throws VaadinConfigurationException {
         return new DefaultDeploymentConfiguration(systemPropertyBaseClass,
-                createInitParameters(systemPropertyBaseClass, servletConfig));
+                createInitParameters(systemPropertyBaseClass, vaadinConfig));
     }
 
     /**
@@ -123,18 +123,16 @@ public static DeploymentConfiguration createDeploymentConfiguration(
      *
      * @param systemPropertyBaseClass
      *            the class to look for properties defined with annotations
-     * @param servletConfig
+     * @param vaadinConfig
      *            the config to get the rest of the properties from
      * @return {@link DeploymentConfiguration} instance
-     * @throws ServletException
-     *             if construction of the {@link Properties} for the parameters
-     *             fails
+     * @throws VaadinConfigurationException thrown if property construction fails
      */
     public static DeploymentConfiguration createPropertyDeploymentConfiguration(
-            Class systemPropertyBaseClass, ServletConfig servletConfig)
-            throws ServletException {
+            Class systemPropertyBaseClass, VaadinConfig vaadinConfig)
+            throws VaadinConfigurationException {
         return new PropertyDeploymentConfiguration(systemPropertyBaseClass,
-                createInitParameters(systemPropertyBaseClass, servletConfig));
+                createInitParameters(systemPropertyBaseClass, vaadinConfig));
     }
 
     /**
@@ -142,35 +140,33 @@ public static DeploymentConfiguration createPropertyDeploymentConfiguration(
      * in current application.
      *
      * @param systemPropertyBaseClass
-     *            the class to look for properties defined with annotations
-     * @param servletConfig
-     *            the config to get the rest of the properties from
+     *         the class to look for properties defined with annotations
+     * @param vaadinConfig
+     *         the config to get the rest of the properties from
      * @return {@link Properties} instance
-     * @throws ServletException
-     *             if construction of the {@link Properties} for the parameters
-     *             fails
+     * @throws VaadinConfigurationException thrown if property construction fails
      */
     protected static Properties createInitParameters(
-            Class systemPropertyBaseClass, ServletConfig servletConfig)
-            throws ServletException {
+            Class systemPropertyBaseClass, VaadinConfig vaadinConfig)
+            throws VaadinConfigurationException {
         Properties initParameters = new Properties();
         readUiFromEnclosingClass(systemPropertyBaseClass, initParameters);
         readConfigurationAnnotation(systemPropertyBaseClass, initParameters);
 
         // Read default parameters from server.xml
-        final ServletContext context = servletConfig.getServletContext();
-        for (final Enumeration e = context.getInitParameterNames(); e
+        final VaadinContext context = vaadinConfig.getVaadinContext();
+        for (final Enumeration e = context.getContextParameterNames(); e
                 .hasMoreElements();) {
             final String name = e.nextElement();
-            initParameters.setProperty(name, context.getInitParameter(name));
+            initParameters.setProperty(name, context.getContextParameter(name));
         }
 
         // Override with application config from web.xml
-        for (final Enumeration e = servletConfig
-                .getInitParameterNames(); e.hasMoreElements();) {
+        for (final Enumeration e = vaadinConfig
+                .getConfigParameterNames(); e.hasMoreElements(); ) {
             final String name = e.nextElement();
-            initParameters.setProperty(name,
-                    servletConfig.getInitParameter(name));
+            initParameters
+                    .setProperty(name, vaadinConfig.getConfigParameter(name));
         }
 
         readBuildInfo(initParameters);
@@ -184,6 +180,24 @@ private static void readBuildInfo(Properties initParameters) {
         // already set.
         if (json != null) {
             JsonObject buildInfo = JsonUtil.parse(json);
+            if (buildInfo.hasKey(EXTERNAL_STATS_FILE_TOKEN) || buildInfo
+                    .hasKey(EXTERNAL_STATS_URL_TOKEN)) {
+                // If external stats file is flagged then we should always run in
+                // npm production mode.
+                initParameters.setProperty(SERVLET_PARAMETER_PRODUCTION_MODE,
+                        Boolean.toString(true));
+                initParameters.setProperty(SERVLET_PARAMETER_COMPATIBILITY_MODE,
+                        Boolean.toString(false));
+                initParameters.setProperty(SERVLET_PARAMETER_ENABLE_DEV_SERVER,
+                        Boolean.toString(false));
+                initParameters.setProperty(EXTERNAL_STATS_FILE,
+                        Boolean.toString(true));
+                if (buildInfo.hasKey(EXTERNAL_STATS_URL_TOKEN)) {
+                    initParameters.setProperty(EXTERNAL_STATS_URL,
+                            buildInfo.getString(EXTERNAL_STATS_URL_TOKEN));
+                }
+                return;
+            }
             if (buildInfo.hasKey(SERVLET_PARAMETER_PRODUCTION_MODE)) {
                 initParameters.setProperty(SERVLET_PARAMETER_PRODUCTION_MODE,
                         String.valueOf(buildInfo.getBoolean(
@@ -293,7 +307,7 @@ private static String getTokenFileContents(Properties initParameters) {
         try {
             json = getResourceFromFile(initParameters);
             if (json == null) {
-                json = getResourceFromClassloader(initParameters);
+                json = getResourceFromClassloader();
             }
         } catch (IOException e) {
             throw new UncheckedIOException(e);
@@ -316,7 +330,7 @@ private static String getResourceFromFile(Properties initParameters)
         return json;
     }
 
-    private static String getResourceFromClassloader(Properties initParameters)
+    private static String getResourceFromClassloader()
             throws IOException {
         String json = null;
         // token file is in the class-path of the application
@@ -329,10 +343,11 @@ private static String getResourceFromClassloader(Properties initParameters)
         URL resource = resources.stream()
                 .filter(url -> !url.getPath().endsWith("jar!/" + tokenResource))
                 .findFirst().orElse(null);
-        if (resource == null && isProductionMode(initParameters)) {
-            // For no non jar build info, in production mode check jar files
-            // for production mode jar.
-            json = getProductionModeResource(resources);
+        if (resource == null && !resources.isEmpty()) {
+            // For no non jar build info, in production mode check for
+            // webpack.generated.json if it's in a jar in a jar then accept
+            // single jar flow-build-info.
+            json = getPossibleJarResource(resources);
         } else if (resource != null) {
             json = FrontendUtils.streamToString(resource.openStream());
         }
@@ -366,30 +381,39 @@ private static boolean isProductionMode(Properties initParameters) {
     }
 
     /**
-     * Check resources for a production mode resource if all resources were
-     * from JAR files as we may be running from a JAR and add-ons are not
-     * packaged in productionMode.
+     * Check if the webpack.generated.js resources is inside 2 jars
+     * (flow-server.jar and application.jar) if this is the case then we can
+     * accept a build info file from inside  jar with a single jar in the path.
      *
      * @param resources
      *         flow-build-info url resource files
-     * @return production mode flow-build-info string
+     * @return flow-build-info json string or null if no applicable files found
      * @throws IOException
      *         exception reading stream
      */
-    private static String getProductionModeResource(List resources)
+    private static String getPossibleJarResource(List resources)
             throws IOException {
-        for (URL resource : resources) {
-            String json = FrontendUtils.streamToString(resource.openStream());
-            if (json != null && !json.contains(NPM_TOKEN) && !json
-                    .contains(FRONTEND_TOKEN) && json
-                    .contains("\"productionMode\": true")) {
-                return json;
+        URL webpackGenerated = DeploymentConfiguration.class.getClassLoader()
+                .getResource(FrontendUtils.WEBPACK_GENERATED);
+        // If jar!/ exists 2 times for webpack.generated.json then we are
+        // running from a jar
+        if (countInstances(webpackGenerated.getPath(), "jar!/") >= 2) {
+            for (URL resource : resources) {
+                // As we now know that we are running from a jar we can accept a
+                // build info with a single jar in the path
+                if (countInstances(resource.getPath(), "jar!/") == 1) {
+                    return FrontendUtils.streamToString(resource.openStream());
+                }
             }
         }
         // No applicable resources found.
         return null;
     }
 
+    private static int countInstances(String input, String value) {
+        return input.split(value, -1).length - 1;
+    }
+
     /**
      * Verify that given folder actually exists on the system if we are not in
      * production mode.
@@ -468,9 +492,21 @@ private static void readUiFromEnclosingClass(
         }
     }
 
+    /**
+     * Read the VaadinServletConfiguration annotation for initialization name
+     * value pairs and add them to the intial properties object.
+     *
+     * @param systemPropertyBaseClass
+     *         base class for constructing the configuration
+     * @param initParameters
+     *         current initParameters object
+     * @throws VaadinConfigurationException
+     *         exception thrown for failure in invoking method on configuration
+     *         annotation
+     */
     private static void readConfigurationAnnotation(
             Class systemPropertyBaseClass, Properties initParameters)
-            throws ServletException {
+            throws VaadinConfigurationException {
         Optional optionalConfigAnnotation = AnnotationReader
                 .getAnnotationFor(systemPropertyBaseClass,
                         VaadinServletConfiguration.class);
@@ -500,14 +536,12 @@ private static void readConfigurationAnnotation(
                 }
 
                 initParameters.setProperty(name.value(), stringValue);
-            } catch (Exception e) {
+            } catch (IllegalAccessException | InvocationTargetException e) {
                 // This should never happen
-                throw new ServletException(
+                throw new VaadinConfigurationException(
                         "Could not read @VaadinServletConfiguration value "
-                                + method.getName(),
-                        e);
+                                + method.getName(), e);
             }
         }
-
     }
 }
diff --git a/flow-server/src/main/java/com/vaadin/flow/server/DevModeHandler.java b/flow-server/src/main/java/com/vaadin/flow/server/DevModeHandler.java
index 2cc4eab0a78..64a416e7d29 100644
--- a/flow-server/src/main/java/com/vaadin/flow/server/DevModeHandler.java
+++ b/flow-server/src/main/java/com/vaadin/flow/server/DevModeHandler.java
@@ -23,7 +23,6 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
-import java.io.Serializable;
 import java.io.UncheckedIOException;
 import java.lang.management.ManagementFactory;
 import java.net.HttpURLConnection;
@@ -69,7 +68,7 @@
  *
  * @since 2.0
  */
-public final class DevModeHandler implements Serializable {
+public final class DevModeHandler {
 
     private static final AtomicReference atomicHandler = new AtomicReference<>();
 
@@ -105,9 +104,9 @@ public final class DevModeHandler implements Serializable {
     public static final String WEBPACK_SERVER = "node_modules/webpack-dev-server/bin/webpack-dev-server.js";
 
     private int port;
-    private transient Process webpackProcess;
+    private Process webpackProcess;
     private final boolean reuseDevServer;
-    private transient DevServerWatchDog watchDog;
+    private DevServerWatchDog watchDog;
 
     private StringBuilder cumulativeOutput = new StringBuilder();
 
diff --git a/flow-server/src/main/java/com/vaadin/flow/server/ExecutionFailedException.java b/flow-server/src/main/java/com/vaadin/flow/server/ExecutionFailedException.java
index b0f1e64c0c6..644450513bf 100644
--- a/flow-server/src/main/java/com/vaadin/flow/server/ExecutionFailedException.java
+++ b/flow-server/src/main/java/com/vaadin/flow/server/ExecutionFailedException.java
@@ -21,7 +21,6 @@
  * @author Vaadin Ltd
  * @since 2.0
  *
- * @see FallibleCommand
  */
 public class ExecutionFailedException extends Exception {
 
diff --git a/flow-server/src/main/java/com/vaadin/flow/server/FallibleCommand.java b/flow-server/src/main/java/com/vaadin/flow/server/FallibleCommand.java
index 495a955f8a0..68409daf099 100644
--- a/flow-server/src/main/java/com/vaadin/flow/server/FallibleCommand.java
+++ b/flow-server/src/main/java/com/vaadin/flow/server/FallibleCommand.java
@@ -22,7 +22,10 @@
  *
  * @author Vaadin Ltd
  * @since 2.0
+ * @deprecated this command is an internal command and is not supposed to be
+ *             used in application code
  */
+@Deprecated
 public interface FallibleCommand extends Serializable {
 
     /**
diff --git a/flow-server/src/main/java/com/vaadin/flow/server/VaadinConfig.java b/flow-server/src/main/java/com/vaadin/flow/server/VaadinConfig.java
new file mode 100644
index 00000000000..d816efa414d
--- /dev/null
+++ b/flow-server/src/main/java/com/vaadin/flow/server/VaadinConfig.java
@@ -0,0 +1,56 @@
+/*
+ * Copyright 2000-2019 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.flow.server;
+
+import java.io.Serializable;
+import java.util.Enumeration;
+
+/**
+ * Configuration in which {@link VaadinService} is running.
+ * This is a wrapper for Config objects for instance ServletConfig
+ * and PortletConfig.
+ *
+ * @since
+ */
+public interface VaadinConfig extends Serializable {
+
+    /**
+     * Get the VaadinContext for this configuration.
+     *
+     * @return VaadinContext object for this VaadinConfiguration
+     */
+    VaadinContext getVaadinContext();
+
+    /**
+     * Returns the names of the initialization parameters as an
+     * Enumeration, or an empty Enumeration if there
+     * are o initialization parameters.
+     *
+     * @return initialization parameters as a Enumeration
+     */
+    Enumeration getConfigParameterNames();
+
+    /**
+     * Returns the value for the requested parameter, or null if
+     * the parameter does not exist.
+     *
+     * @param name
+     *         name of the parameter whose value is requested
+     * @return parameter value as String or null for
+     * no parameter
+     */
+    String getConfigParameter(String name);
+}
diff --git a/flow-server/src/main/java/com/vaadin/flow/server/VaadinConfigurationException.java b/flow-server/src/main/java/com/vaadin/flow/server/VaadinConfigurationException.java
new file mode 100644
index 00000000000..b2178b3d116
--- /dev/null
+++ b/flow-server/src/main/java/com/vaadin/flow/server/VaadinConfigurationException.java
@@ -0,0 +1,35 @@
+/*
+ * Copyright 2000-2019 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.flow.server;
+
+/**
+ * Exception thrown for failures in the generation of a deployment configuration
+ * object.
+ */
+public class VaadinConfigurationException extends Exception {
+
+    /**
+     * Exception constructor.
+     *
+     * @param message
+     *         exception message
+     * @param exception
+     *         exception cause
+     */
+    public VaadinConfigurationException(String message, Exception exception) {
+        super(message, exception);
+    }
+}
diff --git a/flow-server/src/main/java/com/vaadin/flow/server/VaadinContext.java b/flow-server/src/main/java/com/vaadin/flow/server/VaadinContext.java
index 9d4cfc05b77..6ccb244fcc2 100644
--- a/flow-server/src/main/java/com/vaadin/flow/server/VaadinContext.java
+++ b/flow-server/src/main/java/com/vaadin/flow/server/VaadinContext.java
@@ -16,15 +16,17 @@
 package com.vaadin.flow.server;
 
 import java.io.Serializable;
+import java.util.Enumeration;
 import java.util.function.Supplier;
 
 /**
  * Context in which {@link VaadinService} is running.
  *
- * It is used to store service-scoped attributes.
+ * This is used to store service-scoped attributes and also works as a wrapper
+ * for context objects with properties e.g. ServletContext and
+ * PortletContext
  *
- * @author miki
- * @since 14.0.0
+ * @since 2.0.0
  */
 public interface VaadinContext extends Serializable {
 
@@ -73,4 +75,24 @@ default  T getAttribute(Class type) {
      * @see #setAttribute(Object) for setting attributes.
      */
     void removeAttribute(Class clazz);
+
+    /**
+     * Returns the names of the initialization parameters as an
+     * Enumeration, or an empty Enumeration if there
+     * are o initialization parameters.
+     *
+     * @return initialization parameters as a Enumeration
+     */
+    Enumeration getContextParameterNames();
+
+    /**
+     * Returns the value for the requested parameter, or null if
+     * the parameter does not exist.
+     *
+     * @param name
+     *         name of the parameter whose value is requested
+     * @return parameter value as String or null for
+     * no parameter
+     */
+    String getContextParameter(String name);
 }
diff --git a/flow-server/src/main/java/com/vaadin/flow/server/VaadinService.java b/flow-server/src/main/java/com/vaadin/flow/server/VaadinService.java
index 9a9e23e8346..fcb9f55d384 100644
--- a/flow-server/src/main/java/com/vaadin/flow/server/VaadinService.java
+++ b/flow-server/src/main/java/com/vaadin/flow/server/VaadinService.java
@@ -1786,14 +1786,21 @@ private static String wrapJsonForClient(JsonObject json) {
     /**
      * Creates the JSON to send to the client when the session has expired.
      *
+     * @param async
+     *            a boolean indicating whether the message is sent synchronously
+     *            or asynchronously.
      * @return the JSON used to inform the client about a session expiration, as
      *         a string
      */
-    public static String createSessionExpiredJSON() {
+    public static String createSessionExpiredJSON(boolean async) {
         JsonObject json = Json.createObject();
         JsonObject meta = Json.createObject();
         json.put("meta", meta);
 
+        if (async) {
+            meta.put(JsonConstants.META_ASYNC, true);
+        }
+
         meta.put(JsonConstants.META_SESSION_EXPIRED, true);
         return wrapJsonForClient(json);
     }
@@ -1801,14 +1808,17 @@ public static String createSessionExpiredJSON() {
     /**
      * Creates the JSON to send to the client when the UI cannot be found.
      *
+     * @param async
+     *            a boolean indicating whether the message is sent synchronously
+     *            or asynchronously.
      * @return the JSON used to inform the client that the UI cannot be found,
      *         as a string
      */
-    public static String createUINotFoundJSON() {
+    public static String createUINotFoundJSON(boolean async) {
         // Session Expired is technically not really the correct thing as
         // the session exists but the requested UI does not. Still we want
         // to handle it the same way on the client side.
-        return createSessionExpiredJSON();
+        return createSessionExpiredJSON(async);
     }
 
     private static void putValueOrJsonNull(JsonObject json, String key,
diff --git a/flow-server/src/main/java/com/vaadin/flow/server/VaadinServlet.java b/flow-server/src/main/java/com/vaadin/flow/server/VaadinServlet.java
index 3a29070db1c..d2aba277bdd 100644
--- a/flow-server/src/main/java/com/vaadin/flow/server/VaadinServlet.java
+++ b/flow-server/src/main/java/com/vaadin/flow/server/VaadinServlet.java
@@ -20,6 +20,7 @@
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
+
 import java.io.IOException;
 import java.net.MalformedURLException;
 import java.net.URL;
@@ -50,7 +51,6 @@
 public class VaadinServlet extends HttpServlet {
     private VaadinServletService servletService;
     private StaticFileHandler staticFileHandler;
-    private DevModeHandler devmodeHandler;
     private WebJarServer webJarServer;
 
     /**
@@ -81,7 +81,6 @@ public void init(ServletConfig servletConfig) throws ServletException {
         if (deploymentConfiguration.areWebJarsEnabled()) {
             webJarServer = new WebJarServer(deploymentConfiguration);
         }
-        devmodeHandler = DevModeHandler.getDevModeHandler();
 
         // Sets current service even though there are no request and response
         servletService.setCurrentInstances(null, null);
@@ -140,16 +139,17 @@ public static VaadinServlet getCurrent() {
      * frameworks.
      *
      * @return the created deployment configuration
-     *
-     * @throws ServletException
-     *             if construction of the {@link Properties} for
-     *             {@link DeploymentConfigurationFactory#createInitParameters(Class, ServletConfig)}
-     *             fails
      */
     protected DeploymentConfiguration createDeploymentConfiguration()
             throws ServletException {
-        return createDeploymentConfiguration(DeploymentConfigurationFactory
-                .createInitParameters(getClass(), getServletConfig()));
+        try {
+            return createDeploymentConfiguration(DeploymentConfigurationFactory
+                    .createInitParameters(getClass(),
+                            new VaadinServletConfig(getServletConfig())));
+        } catch (VaadinConfigurationException e) {
+            throw new ServletException(
+                    "Failed to construct DeploymentConfiguration.", e);
+        }
     }
 
     /**
@@ -274,9 +274,10 @@ protected void service(HttpServletRequest request,
      */
     protected boolean serveStaticOrWebJarRequest(HttpServletRequest request,
             HttpServletResponse response) throws IOException {
+        DevModeHandler handler = DevModeHandler.getDevModeHandler();
 
-        if (devmodeHandler != null && devmodeHandler.isDevModeRequest(request)
-                && devmodeHandler.serveDevModeRequest(request, response)) {
+        if (handler != null && handler.isDevModeRequest(request)
+                && handler.serveDevModeRequest(request, response)) {
             return true;
         }
 
diff --git a/flow-server/src/main/java/com/vaadin/flow/server/VaadinServletConfig.java b/flow-server/src/main/java/com/vaadin/flow/server/VaadinServletConfig.java
new file mode 100644
index 00000000000..1d175936734
--- /dev/null
+++ b/flow-server/src/main/java/com/vaadin/flow/server/VaadinServletConfig.java
@@ -0,0 +1,73 @@
+/*
+ * Copyright 2000-2019 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.flow.server;
+
+import javax.servlet.ServletConfig;
+import java.util.Enumeration;
+import java.util.Objects;
+
+/**
+ * {@link VaadinConfig} implementation for Servlets.
+ *
+ * @since
+ */
+public class VaadinServletConfig implements VaadinConfig {
+
+    private transient ServletConfig config;
+
+    /**
+     * Vaadin servlet configuration wrapper constructor.
+     *
+     * @param config
+     *         servlet configuration object, not null
+     */
+    public VaadinServletConfig(ServletConfig config) {
+        Objects.requireNonNull(config, "VaadinServletConfig requires the ServletConfig object");
+        this.config = config;
+    }
+
+    /**
+     * Ensures there is a valid instance of {@link ServletConfig}.
+     */
+    private void ensureServletConfig() {
+        if (config == null && VaadinService
+                .getCurrent() instanceof VaadinServletService) {
+            config = ((VaadinServletService) VaadinService.getCurrent())
+                    .getServlet().getServletConfig();
+        } else if (config == null) {
+            throw new IllegalStateException(
+                    "The underlying ServletContext of VaadinServletContext is null and there is no VaadinServletService to obtain it from.");
+        }
+    }
+
+    @Override
+    public VaadinContext getVaadinContext() {
+        ensureServletConfig();
+        return new VaadinServletContext(config.getServletContext());
+    }
+
+    @Override
+    public Enumeration getConfigParameterNames() {
+        ensureServletConfig();
+        return config.getInitParameterNames();
+    }
+
+    @Override
+    public String getConfigParameter(String name) {
+        ensureServletConfig();
+        return config.getInitParameter(name);
+    }
+}
diff --git a/flow-server/src/main/java/com/vaadin/flow/server/VaadinServletContext.java b/flow-server/src/main/java/com/vaadin/flow/server/VaadinServletContext.java
index b0dc0178b3f..7bda9b4822f 100644
--- a/flow-server/src/main/java/com/vaadin/flow/server/VaadinServletContext.java
+++ b/flow-server/src/main/java/com/vaadin/flow/server/VaadinServletContext.java
@@ -16,12 +16,13 @@
 package com.vaadin.flow.server;
 
 import javax.servlet.ServletContext;
+import java.util.Enumeration;
 import java.util.function.Supplier;
 
 /**
  * {@link VaadinContext} that goes with {@link VaadinServletService}.
- * @author miki
- * @since 14.0.0
+ *
+ * @since 2.0.0
  */
 public class VaadinServletContext implements VaadinContext {
 
@@ -80,4 +81,16 @@ public void removeAttribute(Class clazz) {
         context.removeAttribute(clazz.getName());
     }
 
+    @Override
+    public Enumeration getContextParameterNames() {
+        ensureServletContext();
+        return context.getInitParameterNames();
+    }
+
+    @Override
+    public String getContextParameter(String name) {
+        ensureServletContext();
+        return context.getInitParameter(name);
+    }
+
 }
diff --git a/flow-server/src/main/java/com/vaadin/flow/server/communication/MetadataWriter.java b/flow-server/src/main/java/com/vaadin/flow/server/communication/MetadataWriter.java
index a91947cad96..0a459641f02 100644
--- a/flow-server/src/main/java/com/vaadin/flow/server/communication/MetadataWriter.java
+++ b/flow-server/src/main/java/com/vaadin/flow/server/communication/MetadataWriter.java
@@ -20,6 +20,8 @@
 
 import com.vaadin.flow.component.UI;
 import com.vaadin.flow.server.SystemMessages;
+import com.vaadin.flow.server.VaadinSessionState;
+import com.vaadin.flow.shared.JsonConstants;
 
 import elemental.json.Json;
 import elemental.json.JsonObject;
@@ -59,7 +61,12 @@ public JsonObject createMetadata(UI ui, boolean repaintAll, boolean async,
         }
 
         if (async) {
-            meta.put("async", true);
+            meta.put(JsonConstants.META_ASYNC, true);
+        }
+
+        VaadinSessionState state = ui.getSession().getState();
+        if (state != null && state.compareTo(VaadinSessionState.CLOSING) >= 0) {
+            meta.put(JsonConstants.META_SESSION_EXPIRED, true);
         }
 
         // meta instruction for client to enable auto-forward to
diff --git a/flow-server/src/main/java/com/vaadin/flow/server/communication/PushHandler.java b/flow-server/src/main/java/com/vaadin/flow/server/communication/PushHandler.java
index c4477bb182f..2d7d0600a9f 100644
--- a/flow-server/src/main/java/com/vaadin/flow/server/communication/PushHandler.java
+++ b/flow-server/src/main/java/com/vaadin/flow/server/communication/PushHandler.java
@@ -70,10 +70,10 @@ private interface PushEventCallback {
      * open by calling resource.suspend(). If there is a pending push, send it
      * now.
      */
-    private final PushEventCallback establishCallback = ( resource,  ui) -> {
-            getLogger().debug(
-                    "New push connection for resource {} with transport {}",
-                     resource.uuid(), resource.transport() );
+    private final PushEventCallback establishCallback = (resource, ui) -> {
+        getLogger().debug(
+                "New push connection for resource {} with transport {}",
+                resource.uuid(), resource.transport());
 
         resource.getResponse().setContentType("text/plain; charset=UTF-8");
 
@@ -105,8 +105,7 @@ private interface PushEventCallback {
      * respond to the request directly.)
      */
     private final PushEventCallback receiveCallback = (resource, ui) -> {
-        getLogger().debug("Received message from resource {}",
-                resource.uuid());
+        getLogger().debug("Received message from resource {}", resource.uuid());
 
         AtmosphereRequest req = resource.getRequest();
 
@@ -137,8 +136,7 @@ private interface PushEventCallback {
             // Refresh on client side
             sendRefreshAndDisconnect(resource);
         } catch (InvalidUIDLSecurityKeyException e) {
-            getLogger().warn(
-                    "Invalid security key received from {}",
+            getLogger().warn("Invalid security key received from {}",
                     resource.getRequest().getRemoteHost());
             // Refresh on client side
             sendRefreshAndDisconnect(resource);
@@ -200,7 +198,7 @@ private void callWithUi(final AtmosphereResource resource,
                 assert VaadinSession.getCurrent() == session;
             } catch (SessionExpiredException e) {
                 sendNotificationAndDisconnect(resource,
-                        VaadinService.createSessionExpiredJSON());
+                        VaadinService.createSessionExpiredJSON(true));
                 return;
             }
 
@@ -212,7 +210,7 @@ private void callWithUi(final AtmosphereResource resource,
 
                 if (ui == null) {
                     sendNotificationAndDisconnect(resource,
-                            VaadinService.createUINotFoundJSON());
+                            VaadinService.createUINotFoundJSON(true));
                 } else {
                     callback.run(resource, ui);
                 }
@@ -244,8 +242,7 @@ private void callWithUi(final AtmosphereResource resource,
                 try {
                     session.unlock();
                 } catch (Exception e) {
-                    getLogger().warn(
-                            "Error while unlocking session", e);
+                    getLogger().warn("Error while unlocking session", e);
                     // can't call ErrorHandler, we (hopefully) don't have a lock
                 }
             }
@@ -280,8 +277,7 @@ private static AtmospherePushConnection getConnectionForUI(UI ui) {
 
     void connectionLost(AtmosphereResourceEvent event) {
         if (event == null) {
-            getLogger().error(
-                    "Could not get event. This should never happen.");
+            getLogger().error("Could not get event. This should never happen.");
             return;
         }
         // We don't want to use callWithUi here, as it assumes there's a client
@@ -290,8 +286,6 @@ void connectionLost(AtmosphereResourceEvent event) {
 
         AtmosphereResource resource = event.getResource();
         if (resource == null) {
-            getLogger().error(
-                    "Could not get resource. This should never happen.");
             return;
         }
         VaadinServletRequest vaadinRequest = new VaadinServletRequest(
@@ -330,8 +324,8 @@ void connectionLost(AtmosphereResourceEvent event) {
                 ui = findUiUsingResource(resource, session.getUIs());
 
                 if (ui == null) {
-                    getLogger().debug(
-                            "Could not get UI. This should never happen,"
+                    getLogger()
+                            .debug("Could not get UI. This should never happen,"
                                     + " except when reloading in Firefox and Chrome -"
                                     + " see http://dev.vaadin.com/ticket/14251.");
                     return;
@@ -358,8 +352,7 @@ void connectionLost(AtmosphereResourceEvent event) {
                      * The client is expected to close the connection after push
                      * mode has been set to disabled.
                      */
-                    getLogger().debug(
-                            "Connection closed for resource {}", id);
+                    getLogger().debug("Connection closed for resource {}", id);
                 } else {
                     /*
                      * Unexpected cancel, e.g. if the user closes the browser
@@ -379,8 +372,7 @@ void connectionLost(AtmosphereResourceEvent event) {
             try {
                 session.unlock();
             } catch (Exception e) {
-                getLogger().warn("Error while unlocking session",
-                        e);
+                getLogger().warn("Error while unlocking session", e);
                 // can't call ErrorHandler, we (hopefully) don't have a lock
             }
         }
@@ -441,8 +433,8 @@ private static void sendNotificationAndDisconnect(
             resource.getResponse().getWriter().write(notificationJson);
             resource.resume();
         } catch (Exception e) {
-            getLogger().trace(
-                    "Failed to send critical notification to client", e);
+            getLogger().trace("Failed to send critical notification to client",
+                    e);
         }
     }
 
diff --git a/flow-server/src/main/java/com/vaadin/flow/server/communication/ServerRpcHandler.java b/flow-server/src/main/java/com/vaadin/flow/server/communication/ServerRpcHandler.java
index e875123b396..c8507195ed3 100644
--- a/flow-server/src/main/java/com/vaadin/flow/server/communication/ServerRpcHandler.java
+++ b/flow-server/src/main/java/com/vaadin/flow/server/communication/ServerRpcHandler.java
@@ -35,6 +35,7 @@
 
 import com.vaadin.flow.component.UI;
 import com.vaadin.flow.internal.MessageDigestUtil;
+import com.vaadin.flow.internal.StateNode;
 import com.vaadin.flow.server.ErrorEvent;
 import com.vaadin.flow.server.VaadinRequest;
 import com.vaadin.flow.server.VaadinService;
@@ -208,6 +209,20 @@ public InvalidUIDLSecurityKeyException() {
         }
     }
 
+    /**
+     * Exception thrown then the client side resynchronization is required.
+     */
+    public static class ResynchronizationRequiredException
+            extends RuntimeException {
+
+        /**
+         * Default constructor for the exception.
+         */
+        public ResynchronizationRequiredException() {
+            super();
+        }
+    }
+
     /**
      * Reads JSON containing zero or more serialized RPC calls (including legacy
      * variable changes) and executes the calls.
@@ -302,10 +317,17 @@ public void handleRpc(UI ui, Reader reader, VaadinRequest request)
         }
 
         if (rpcRequest.isResynchronize()) {
-            // FIXME Implement
-            throw new UnsupportedOperationException("FIXME: Implement resync");
+            getLogger().warn("Resynchronizing UI by client's request. Under "
+                    + "normal operations this should not happen and may "
+                    + "indicate a bug in Vaadin platform. If you see this "
+                    + "message regularly please open a bug report at "
+                    + "https://github.com/vaadin/flow/issues");
+            ui.getInternals().getStateTree().getRootNode()
+                    .visitNodeTree(StateNode::markAsDirty);
+            // Signal by exception instead of return value to keep the method
+            // signature for source and binary compatibility
+            throw new ResynchronizationRequiredException();
         }
-
     }
 
     /**
diff --git a/flow-server/src/main/java/com/vaadin/flow/server/communication/UidlRequestHandler.java b/flow-server/src/main/java/com/vaadin/flow/server/communication/UidlRequestHandler.java
index db5b2270270..8479ce31f94 100644
--- a/flow-server/src/main/java/com/vaadin/flow/server/communication/UidlRequestHandler.java
+++ b/flow-server/src/main/java/com/vaadin/flow/server/communication/UidlRequestHandler.java
@@ -36,6 +36,7 @@
 import com.vaadin.flow.server.VaadinService;
 import com.vaadin.flow.server.VaadinSession;
 import com.vaadin.flow.server.communication.ServerRpcHandler.InvalidUIDLSecurityKeyException;
+import com.vaadin.flow.server.communication.ServerRpcHandler.ResynchronizationRequiredException;
 import com.vaadin.flow.shared.JsonConstants;
 
 import elemental.json.JsonException;
@@ -77,7 +78,8 @@ public boolean synchronizedHandleRequest(VaadinSession session,
         if (uI == null) {
             // This should not happen but it will if the UI has been closed. We
             // really don't want to see it in the server logs though
-            commitJsonResponse(response, VaadinService.createUINotFoundJSON());
+            commitJsonResponse(response,
+                    VaadinService.createUINotFoundJSON(false));
             return true;
         }
 
@@ -85,8 +87,7 @@ public boolean synchronizedHandleRequest(VaadinSession session,
 
         try {
             getRpcHandler(session).handleRpc(uI, request.getReader(), request);
-
-            writeUidl(uI, stringWriter);
+            writeUidl(uI, stringWriter, false);
         } catch (JsonException e) {
             getLogger().error("Error writing JSON to response", e);
             // Refresh on client side
@@ -98,6 +99,9 @@ public boolean synchronizedHandleRequest(VaadinSession session,
             // Refresh on client side
             writeRefresh(response);
             return true;
+        } catch (ResynchronizationRequiredException e) { // NOSONAR
+            // Resync on the client side
+            writeUidl(uI, stringWriter, true);
         } finally {
             stringWriter.close();
         }
@@ -112,8 +116,9 @@ private void writeRefresh(VaadinResponse response) throws IOException {
         commitJsonResponse(response, json);
     }
 
-    private static void writeUidl(UI ui, Writer writer) throws IOException {
-        JsonObject uidl = new UidlWriter().createUidl(ui, false);
+    private static void writeUidl(UI ui, Writer writer, boolean resync)
+            throws IOException {
+        JsonObject uidl = new UidlWriter().createUidl(ui, false, resync);
 
         // some dirt to prevent cross site scripting
         String responseString = "for(;;);[" + uidl.toJson() + "]";
@@ -140,7 +145,7 @@ public boolean handleSessionExpired(VaadinRequest request,
         VaadinService service = request.getService();
         service.writeUncachedStringResponse(response,
                 JsonConstants.JSON_CONTENT_TYPE,
-                VaadinService.createSessionExpiredJSON());
+                VaadinService.createSessionExpiredJSON(false));
 
         return true;
     }
diff --git a/flow-server/src/main/java/com/vaadin/flow/server/communication/UidlWriter.java b/flow-server/src/main/java/com/vaadin/flow/server/communication/UidlWriter.java
index 4eb6a62bff3..e761fa2838a 100644
--- a/flow-server/src/main/java/com/vaadin/flow/server/communication/UidlWriter.java
+++ b/flow-server/src/main/java/com/vaadin/flow/server/communication/UidlWriter.java
@@ -141,10 +141,12 @@ public AbstractTheme getTheme() {
      *            The {@link UI} whose changes to write
      * @param async
      *            True if this message is sent by the server asynchronously,
-     *            false if it is a response to a client message.
+     *            false if it is a response to a client message
+     * @param resync
+     *            True iff the client should be asked to resynchronize
      * @return JSON object containing the UIDL response
      */
-    public JsonObject createUidl(UI ui, boolean async) {
+    public JsonObject createUidl(UI ui, boolean async, boolean resync) {
         JsonObject response = Json.createObject();
 
         UIInternals uiInternals = ui.getInternals();
@@ -163,6 +165,9 @@ public JsonObject createUidl(UI ui, boolean async) {
                 ? uiInternals.getServerSyncId() : -1;
 
         response.put(ApplicationConstants.SERVER_SYNC_ID, syncId);
+        if (resync) {
+            response.put(ApplicationConstants.RESYNCHRONIZE_ID, true);
+        }
         int nextClientToServerMessageId = uiInternals
                 .getLastProcessedClientToServerId() + 1;
         response.put(ApplicationConstants.CLIENT_TO_SERVER_ID,
@@ -206,6 +211,20 @@ public JsonObject createUidl(UI ui, boolean async) {
         return response;
     }
 
+    /**
+     * Creates a JSON object containing all pending changes to the given UI.
+     *
+     * @param ui
+     *            The {@link UI} whose changes to write
+     * @param async
+     *            True if this message is sent by the server asynchronously,
+     *            false if it is a response to a client message.
+     * @return JSON object containing the UIDL response
+     */
+    public JsonObject createUidl(UI ui, boolean async) {
+        return createUidl(ui, async, false);
+    }
+
     private static void populateDependencies(JsonObject response,
             DependencyList dependencyList, ResolveContext context) {
         Collection pendingSendToClient = dependencyList
diff --git a/flow-server/src/main/java/com/vaadin/flow/server/communication/WebComponentBootstrapHandler.java b/flow-server/src/main/java/com/vaadin/flow/server/communication/WebComponentBootstrapHandler.java
index abe69f855a1..ef4dccf63ea 100644
--- a/flow-server/src/main/java/com/vaadin/flow/server/communication/WebComponentBootstrapHandler.java
+++ b/flow-server/src/main/java/com/vaadin/flow/server/communication/WebComponentBootstrapHandler.java
@@ -15,11 +15,27 @@
  */
 package com.vaadin.flow.server.communication;
 
+import java.io.BufferedWriter;
+import java.io.IOException;
+import java.io.OutputStreamWriter;
+import java.io.Writer;
+import java.lang.annotation.Annotation;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.util.Optional;
+import java.util.function.Function;
+import java.util.regex.Pattern;
+
+import org.jsoup.nodes.Attribute;
+import org.jsoup.nodes.Document;
+import org.jsoup.nodes.Element;
+
 import com.vaadin.flow.component.PushConfiguration;
 import com.vaadin.flow.component.UI;
 import com.vaadin.flow.component.webcomponent.WebComponentUI;
 import com.vaadin.flow.internal.JsonUtils;
 import com.vaadin.flow.server.BootstrapHandler;
+import com.vaadin.flow.server.Constants;
 import com.vaadin.flow.server.ServletHelper;
 import com.vaadin.flow.server.VaadinRequest;
 import com.vaadin.flow.server.VaadinResponse;
@@ -33,25 +49,10 @@
 import elemental.json.Json;
 import elemental.json.JsonArray;
 import elemental.json.JsonObject;
-import org.jsoup.nodes.Attribute;
-import org.jsoup.nodes.Document;
-import org.jsoup.nodes.Element;
-
-import java.io.BufferedWriter;
-import java.io.IOException;
-import java.io.OutputStreamWriter;
-import java.io.Writer;
-import java.lang.annotation.Annotation;
-import java.net.URI;
-import java.net.URISyntaxException;
-import java.util.Optional;
-import java.util.function.Function;
-import java.util.regex.Pattern;
 
 import static com.vaadin.flow.shared.ApplicationConstants.CONTENT_TYPE_TEXT_JAVASCRIPT_UTF_8;
 import static java.nio.charset.StandardCharsets.UTF_8;
 
-
 /**
  * Bootstrap handler for WebComponent requests.
  *
@@ -61,15 +62,16 @@
 public class WebComponentBootstrapHandler extends BootstrapHandler {
     private static final String REQ_PARAM_URL = "url";
     private static final String PATH_PREFIX = "/web-component/web-component";
-    private static final Pattern PATH_PATTERN =
-            Pattern.compile(".*" + PATH_PREFIX + "-(ui|bootstrap)\\.(js|html)$");
+    private static final Pattern PATH_PATTERN = Pattern
+            .compile(".*" + PATH_PREFIX + "-(ui|bootstrap)\\.(js|html)$");
 
     private static class WebComponentBootstrapContext extends BootstrapContext {
 
         private WebComponentBootstrapContext(VaadinRequest request,
-                                             VaadinResponse response, UI ui,
-                                             Function callback) {
-            super(request, response, ui.getInternals().getSession(), ui, callback);
+                VaadinResponse response, UI ui,
+                Function callback) {
+            super(request, response, ui.getInternals().getSession(), ui,
+                    callback);
         }
 
         @Override
@@ -82,7 +84,8 @@ public  Optional getPageConfigurationAnnotation(
 
         @Override
         protected Optional getTheme() {
-            Optional optionalTheme = getPageConfigurationAnnotation(Theme.class);
+            Optional optionalTheme = getPageConfigurationAnnotation(
+                    Theme.class);
             return optionalTheme.map(ThemeDefinition::new);
         }
     }
@@ -96,7 +99,9 @@ public WebComponentBootstrapHandler() {
 
     /**
      * Creates a new bootstrap handler, allowing to use custom page builder.
-     * @param pageBuilder Page builder to use.
+     *
+     * @param pageBuilder
+     *            Page builder to use.
      */
     protected WebComponentBootstrapHandler(PageBuilder pageBuilder) {
         super(pageBuilder);
@@ -112,31 +117,36 @@ protected boolean canHandleRequest(VaadinRequest request) {
     }
 
     /**
-     * Returns the request's base url to use in constructing and initialising ui.
-     * @param request Request to the url for.
+     * Returns the request's base url to use in constructing and initialising
+     * ui.
+     *
+     * @param request
+     *            Request to the url for.
      * @return Request's url.
      */
     protected String getRequestUrl(VaadinRequest request) {
-        return ((VaadinServletRequest)request).getRequestURL().toString();
+        return ((VaadinServletRequest) request).getRequestURL().toString();
     }
 
     @Override
-    protected BootstrapContext createAndInitUI(
-            Class uiClass, VaadinRequest request,
-            VaadinResponse response, VaadinSession session) {
+    protected BootstrapContext createAndInitUI(Class uiClass,
+            VaadinRequest request, VaadinResponse response,
+            VaadinSession session) {
+
+        if (!canHandleRequest(request)) {
+            throw new IllegalStateException(
+                    "Unexpected request URL '" + getRequestUrl(request)
+                            + "' in the bootstrap handler for web "
+                            + "component UI which should handle path "
+                            + PATH_PATTERN.toString());
+        }
+
+        final String serviceUrl = getServiceUrl(request, response);
+
         BootstrapContext context = super.createAndInitUI(WebComponentUI.class,
                 request, response, session);
         JsonObject config = context.getApplicationParameters();
 
-        if(!canHandleRequest(request)) {
-            throw new IllegalStateException("Unexpected request URL '"
-                    + getRequestUrl(request) + "' in the bootstrap handler for web "
-                    + "component UI which should handle path "
-                    + PATH_PATTERN.toString());
-        }
-
-        String serviceUrl = getServiceUrl(request);
-
         String pushURL = context.getSession().getConfiguration().getPushURL();
         if (pushURL == null) {
             pushURL = serviceUrl;
@@ -169,26 +179,29 @@ protected BootstrapContext createAndInitUI(
 
     @Override
     protected BootstrapContext createBootstrapContext(VaadinRequest request,
-                                                      VaadinResponse response, UI ui, Function callback) {
-        return new WebComponentBootstrapContext(request, response, ui, callback);
+            VaadinResponse response, UI ui,
+            Function callback) {
+        return new WebComponentBootstrapContext(request, response, ui,
+                callback);
     }
 
-
     @Override
-    public boolean synchronizedHandleRequest(VaadinSession session, VaadinRequest request, VaadinResponse response) throws IOException {
-        if (session.getService().getDeploymentConfiguration().isCompatibilityMode()) {
+    public boolean synchronizedHandleRequest(VaadinSession session,
+            VaadinRequest request, VaadinResponse response) throws IOException {
+        if (session.getService().getDeploymentConfiguration()
+                .isCompatibilityMode()) {
             return super.synchronizedHandleRequest(session, request, response);
         } else {
             // Find UI class
             Class uiClass = getUIClass(request);
 
-            BootstrapContext context = createAndInitUI(uiClass, request, response,
-                    session);
+            BootstrapContext context = createAndInitUI(uiClass, request,
+                    response, session);
 
             ServletHelper.setResponseNoCacheHeaders(response::setHeader,
                     response::setDateHeader);
 
-            String serviceUrl = getServiceUrl(request);
+            String serviceUrl = getServiceUrl(request, response);
 
             Document document = getPageBuilder().getBootstrapPage(context);
             writeBootstrapPage(response, document.head(), serviceUrl);
@@ -202,19 +215,20 @@ public boolean synchronizedHandleRequest(VaadinSession session, VaadinRequest re
      * JavaScript. Drops {@code } element.
      *
      * @param response
-     *         {@link com.vaadin.flow.server.VaadinResponse} into which the
-     *         script is written
+     *            {@link com.vaadin.flow.server.VaadinResponse} into which the
+     *            script is written
      * @param head
-     *         head element of Vaadin Bootstrap page. The child elements are
-     *         copied into the embedding page's head using JavaScript.
+     *            head element of Vaadin Bootstrap page. The child elements are
+     *            copied into the embedding page's head using JavaScript.
      * @param serviceUrl
-     *         base path to use for the head elements' URLs
+     *            base path to use for the head elements' URLs
      * @throws IOException
-     *         if writing fails
+     *             if writing fails
      */
-    private void writeBootstrapPage(
-            VaadinResponse response, Element head, String serviceUrl) throws IOException {
-        writeBootstrapPage(CONTENT_TYPE_TEXT_JAVASCRIPT_UTF_8, response, head, serviceUrl);
+    private void writeBootstrapPage(VaadinResponse response, Element head,
+            String serviceUrl) throws IOException {
+        writeBootstrapPage(CONTENT_TYPE_TEXT_JAVASCRIPT_UTF_8, response, head,
+                serviceUrl);
     }
 
     /**
@@ -223,30 +237,32 @@ private void writeBootstrapPage(
      * JavaScript. Drops {@code } element.
      *
      * @param contentType
-     *          Content type of the response.
+     *            Content type of the response.
      * @param response
-     *         {@link com.vaadin.flow.server.VaadinResponse} into which the
-     *         script is written
+     *            {@link com.vaadin.flow.server.VaadinResponse} into which the
+     *            script is written
      * @param head
-     *         head element of Vaadin Bootstrap page. The child elements are
-     *         copied into the embedding page's head using JavaScript.
+     *            head element of Vaadin Bootstrap page. The child elements are
+     *            copied into the embedding page's head using JavaScript.
      * @param serviceUrl
-     *         base path to use for the head elements' URLs
+     *            base path to use for the head elements' URLs
      * @throws IOException
-     *         if writing fails
+     *             if writing fails
      */
-    protected void writeBootstrapPage(String contentType, VaadinResponse response, Element head, String serviceUrl) throws IOException {
+    protected void writeBootstrapPage(String contentType,
+            VaadinResponse response, Element head, String serviceUrl)
+            throws IOException {
         /*
-            The elements found in the head are reconstructed using JavaScript and
-            document.createElement(...). Since innerHTML and related methods
-            do not execute ")));
-        System.out.println(allElements);
 
         Assert.assertTrue(
                 "index.js should be added to head for ES6 browsers. (deferred and type module)",
diff --git a/flow-server/src/test/java/com/vaadin/flow/server/DeploymentConfigurationFactoryTest.java b/flow-server/src/test/java/com/vaadin/flow/server/DeploymentConfigurationFactoryTest.java
index d1a6a354263..07d9bde184b 100644
--- a/flow-server/src/test/java/com/vaadin/flow/server/DeploymentConfigurationFactoryTest.java
+++ b/flow-server/src/test/java/com/vaadin/flow/server/DeploymentConfigurationFactoryTest.java
@@ -100,7 +100,7 @@ public void servletWithEnclosingUI_hasItsNameInConfig() throws Exception {
 
         DeploymentConfiguration config = DeploymentConfigurationFactory
                 .createDeploymentConfiguration(servlet,
-                        createServletConfigMock(servletConfigParams,
+                        createVaadinConfigMock(servletConfigParams,
                                 Collections.singletonMap(PARAM_TOKEN_FILE,
                                         tokenFile.getPath())));
 
@@ -123,7 +123,7 @@ public void servletWithNoEnclosingUI_hasDefaultUiInConfig()
                 defaultServletParams);
 
         DeploymentConfiguration config = DeploymentConfigurationFactory
-                .createDeploymentConfiguration(servlet, createServletConfigMock(
+                .createDeploymentConfiguration(servlet, createVaadinConfigMock(
                         servletConfigParams, emptyMap()));
 
         Class notUiClass = servlet.getEnclosingClass();
@@ -143,7 +143,7 @@ public void vaadinServletConfigurationRead() throws Exception {
                 defaultServletParams);
 
         DeploymentConfiguration config = DeploymentConfigurationFactory
-                .createDeploymentConfiguration(servlet, createServletConfigMock(
+                .createDeploymentConfiguration(servlet, createVaadinConfigMock(
                         servletConfigParams, emptyMap()));
 
         assertTrue(String.format(
@@ -170,7 +170,7 @@ public void servletConfigParametersOverrideVaadinParameters()
                 Integer.toString(overridingHeartbeatIntervalValue));
 
         DeploymentConfiguration config = DeploymentConfigurationFactory
-                .createDeploymentConfiguration(servlet, createServletConfigMock(
+                .createDeploymentConfiguration(servlet, createVaadinConfigMock(
                         servletConfigParams, emptyMap()));
 
         assertEquals(
@@ -198,7 +198,7 @@ public void servletContextParametersOverrideVaadinParameters()
                 Integer.toString(overridingHeartbeatIntervalValue));
 
         DeploymentConfiguration config = DeploymentConfigurationFactory
-                .createDeploymentConfiguration(servlet, createServletConfigMock(
+                .createDeploymentConfiguration(servlet, createVaadinConfigMock(
                         emptyMap(), servletContextParams));
 
         assertEquals(
@@ -235,7 +235,7 @@ public void servletConfigParametersOverrideServletContextParameters()
                 Integer.toString(servletContextHeartbeatIntervalValue));
 
         DeploymentConfiguration config = DeploymentConfigurationFactory
-                .createDeploymentConfiguration(servlet, createServletConfigMock(
+                .createDeploymentConfiguration(servlet, createVaadinConfigMock(
                         servletConfigParams, servletContextParams));
 
         assertEquals(
@@ -266,7 +266,7 @@ public void should_throwIfCompatibilityModeIsFalseButNoTokenFile()
 
         DeploymentConfigurationFactory.createDeploymentConfiguration(
                 VaadinServlet.class,
-                createServletConfigMock(Collections.singletonMap(
+                createVaadinConfigMock(Collections.singletonMap(
                         Constants.SERVLET_PARAMETER_COMPATIBILITY_MODE,
                         Boolean.FALSE.toString()), emptyMap()));
     }
@@ -285,7 +285,7 @@ public void shouldNotThrowIfCompatibilityModeIsFalse_noTokenFile_correctWebPackC
         FileUtils.writeLines(webPack, Arrays.asList("./webpack.generated.js"));
 
         DeploymentConfigurationFactory.createDeploymentConfiguration(
-                VaadinServlet.class, createServletConfigMock(map, emptyMap()));
+                VaadinServlet.class, createVaadinConfigMock(map, emptyMap()));
     }
 
     @Test
@@ -309,14 +309,16 @@ public void shouldThrowIfCompatibilityModeIsFalse_noTokenFile_incorrectWebPackCo
         webPack.createNewFile();
 
         DeploymentConfigurationFactory.createDeploymentConfiguration(
-                VaadinServlet.class, createServletConfigMock(map, emptyMap()));
+                VaadinServlet.class, createVaadinConfigMock(map, emptyMap()));
     }
 
     @Test
     public void should_readConfigurationFromTokenFile() throws Exception {
         FileUtils.writeLines(tokenFile,
-                Arrays.asList("{", "\"compatibilityMode\": false,",
-                        "\"productionMode\": true", "}"));
+                Arrays.asList("{",
+                        "\"compatibilityMode\": false,",
+                        "\"productionMode\": true",
+                        "}"));
 
         DeploymentConfiguration config = createConfig(Collections
                 .singletonMap(PARAM_TOKEN_FILE, tokenFile.getPath()));
@@ -331,10 +333,13 @@ public void shouldThrow_tokenFileContainsNonExistingNpmFolderInDevMode()
         exception.expectMessage(
                 String.format(DEV_FOLDER_MISSING_MESSAGE, "npm"));
         FileUtils.writeLines(tokenFile,
-                Arrays.asList("{", "\"compatibilityMode\": false,",
-                        "\"productionMode\": false,", "\"npmFolder\": \"npm\",",
+                Arrays.asList("{",
+                        "\"compatibilityMode\": false,",
+                        "\"productionMode\": false,",
+                        "\"npmFolder\": \"npm\",",
                         "\"generatedFolder\": \"generated\",",
-                        "\"frontendFolder\": \"frontend\"", "}"));
+                        "\"frontendFolder\": \"frontend\"",
+                        "}"));
 
         createConfig(Collections.singletonMap(PARAM_TOKEN_FILE,
                 tokenFile.getPath()));
@@ -347,9 +352,11 @@ public void shouldThrow_tokenFileContainsNonExistingFrontendFolderNoNpmFolder()
         exception.expectMessage(
                 String.format(DEV_FOLDER_MISSING_MESSAGE, "frontend"));
         FileUtils.writeLines(tokenFile,
-                Arrays.asList("{", "\"compatibilityMode\": false,",
+                Arrays.asList("{",
+                        "\"compatibilityMode\": false,",
                         "\"productionMode\": false,",
-                        "\"frontendFolder\": \"frontend\"", "}"));
+                        "\"frontendFolder\": \"frontend\"",
+                        "}"));
 
         createConfig(Collections.singletonMap(PARAM_TOKEN_FILE,
                 tokenFile.getPath()));
@@ -365,10 +372,12 @@ public void shouldThrow_tokenFileContainsNonExistingFrontendFolderOutsideNpmSubF
         String tempFolder = temporaryFolder.getRoot().getAbsolutePath()
                 .replace("\\", "/");
         FileUtils.writeLines(tokenFile,
-                Arrays.asList("{", "\"compatibilityMode\": false,",
+                Arrays.asList("{",
+                        "\"compatibilityMode\": false,",
                         "\"productionMode\": false,",
                         "\"npmFolder\": \"" + tempFolder + "/npm\",",
-                        "\"frontendFolder\": \"frontend\"", "}"));
+                        "\"frontendFolder\": \"frontend\"",
+                        "}"));
 
         createConfig(Collections.singletonMap(PARAM_TOKEN_FILE,
                 tokenFile.getPath()));
@@ -381,7 +390,8 @@ public void shouldNotThrow_tokenFileFrontendFolderInDevMode()
         String tempFolder = temporaryFolder.getRoot().getAbsolutePath()
                 .replace("\\", "/");
         FileUtils.writeLines(tokenFile, Arrays.asList("{",
-                "\"compatibilityMode\": false,", "\"productionMode\": false,",
+                "\"compatibilityMode\": false,",
+                "\"productionMode\": false,",
                 "\"npmFolder\": \"" + tempFolder + "/npm\",",
                 "\"frontendFolder\": \"" + tempFolder + "/npm/frontend\"",
                 "}"));
@@ -397,17 +407,72 @@ public void shouldNotThrow_tokenFileFoldersExist() throws Exception {
         String tempFolder = temporaryFolder.getRoot().getAbsolutePath()
                 .replace("\\", "/");
         FileUtils.writeLines(tokenFile, Arrays.asList("{",
-                "\"compatibilityMode\": false,", "\"productionMode\": false,",
+                "\"compatibilityMode\": false,",
+                "\"productionMode\": false,",
                 "\"npmFolder\": \"" + tempFolder + "/npm\",",
-                "\"frontendFolder\": \"" + tempFolder + "/frontend\"", "}"));
+                "\"frontendFolder\": \"" + tempFolder + "/frontend\"",
+                "}"));
 
         createConfig(Collections.singletonMap(PARAM_TOKEN_FILE,
                 tokenFile.getPath()));
     }
 
+    @Test
+    public void externalStatsFileTrue_predefinedContext() throws Exception {
+        FileUtils.writeLines(tokenFile, Arrays.asList("{",
+                "\"externalStatsFile\": true",
+                "}"));
+
+        DeploymentConfiguration config = createConfig(Collections
+                .singletonMap(PARAM_TOKEN_FILE, tokenFile.getPath()));
+
+        assertEquals(true, config.isProductionMode());
+        assertEquals(false, config.isCompatibilityMode());
+        assertEquals(false, config.enableDevServer());
+        assertEquals(true, config.isStatsExternal());
+        assertEquals(Constants.DEFAULT_EXTERNAL_STATS_URL, config.getExternalStatsUrl());
+    }
+
+    @Test
+    public void externalStatsUrlGiven_predefinedContext() throws Exception {
+        FileUtils.writeLines(tokenFile, Arrays.asList("{",
+                "\"externalStatsUrl\": \"http://my.server/static/stats.json\"",
+                "}"));
+
+        DeploymentConfiguration config = createConfig(Collections
+                .singletonMap(PARAM_TOKEN_FILE, tokenFile.getPath()));
+
+        assertEquals(true, config.isProductionMode());
+        assertEquals(false, config.isCompatibilityMode());
+        assertEquals(false, config.enableDevServer());
+        assertEquals(true, config.isStatsExternal());
+        assertEquals("http://my.server/static/stats.json", config.getExternalStatsUrl());
+    }
+
+    @Test
+    public void externalStatsFileTrue_predefinedValuesAreNotOverridden() throws Exception {
+        // note that this situation shouldn't happen that the other settings
+        // would be against the external usage.
+        FileUtils.writeLines(tokenFile, Arrays.asList("{",
+                "\"compatibilityMode\": true,",
+                "\"enableDevServer\": true,",
+                "\"productionMode\": false,",
+                "\"externalStatsFile\": true",
+                "}"));
+
+        DeploymentConfiguration config = createConfig(Collections
+                .singletonMap(PARAM_TOKEN_FILE, tokenFile.getPath()));
+
+        assertEquals(true, config.isProductionMode());
+        assertEquals(false, config.isCompatibilityMode());
+        assertEquals(false, config.enableDevServer());
+        assertEquals(true, config.isStatsExternal());
+        assertEquals(Constants.DEFAULT_EXTERNAL_STATS_URL, config.getExternalStatsUrl());
+    }
+
     @Test
     public void createInitParameters_fallbackChunkObjectIsInInitParams()
-            throws ServletException, IOException {
+            throws VaadinConfigurationException, IOException {
         ServletContext context = Mockito.mock(ServletContext.class);
         ServletConfig config = Mockito.mock(ServletConfig.class);
         Mockito.when(config.getServletContext()).thenReturn(context);
@@ -431,7 +496,7 @@ public void createInitParameters_fallbackChunkObjectIsInInitParams()
                 .thenReturn(tokenFile.getPath());
 
         Properties properties = DeploymentConfigurationFactory
-                .createInitParameters(Object.class, config);
+                .createInitParameters(Object.class, new VaadinServletConfig(config));
 
         Object object = properties
                 .get(DeploymentConfigurationFactory.FALLBACK_CHUNK);
@@ -454,7 +519,13 @@ public void createInitParameters_fallbackChunkObjectIsInInitParams()
     private DeploymentConfiguration createConfig(Map map)
             throws Exception {
         return DeploymentConfigurationFactory.createDeploymentConfiguration(
-                VaadinServlet.class, createServletConfigMock(map, emptyMap()));
+                VaadinServlet.class, createVaadinConfigMock(map, emptyMap()));
+    }
+
+    private VaadinConfig createVaadinConfigMock(
+            Map servletConfigParameters,
+            Map servletContextParameters) throws Exception {
+        return new VaadinServletConfig(createServletConfigMock(servletConfigParameters,servletContextParameters));
     }
 
     private ServletConfig createServletConfigMock(
diff --git a/flow-server/src/test/java/com/vaadin/flow/server/VaadinServletConfigTest.java b/flow-server/src/test/java/com/vaadin/flow/server/VaadinServletConfigTest.java
new file mode 100644
index 00000000000..e9651b681d5
--- /dev/null
+++ b/flow-server/src/test/java/com/vaadin/flow/server/VaadinServletConfigTest.java
@@ -0,0 +1,87 @@
+package com.vaadin.flow.server;
+
+import javax.servlet.ServletConfig;
+import javax.servlet.ServletContext;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+import org.mockito.Mockito;
+
+/**
+ * Test VaadinServletConfig property handling and function with VaadinContext.
+ */
+public class VaadinServletConfigTest {
+
+    private VaadinServletConfig config;
+
+    private ServletContext servletContext;
+    private final Map attributeMap = new HashMap<>();
+    private Map properties;
+
+    @Before
+    public void setup() {
+        ServletConfig servletConfig = Mockito.mock(ServletConfig.class);
+        servletContext = Mockito.mock(ServletContext.class);
+
+        Mockito.when(servletConfig.getServletContext()).thenReturn(servletContext);
+
+        Mockito.when(servletContext.getAttribute(Mockito.anyString()))
+                .then(invocationOnMock -> attributeMap
+                        .get(invocationOnMock.getArguments()[0].toString()));
+        Mockito.doAnswer(invocationOnMock -> attributeMap
+                .put(invocationOnMock.getArguments()[0].toString(),
+                        invocationOnMock.getArguments()[1]))
+                .when(servletContext)
+                .setAttribute(Mockito.anyString(), Mockito.any());
+
+        properties = new HashMap<>();
+        properties.put(Constants.SERVLET_PARAMETER_COMPATIBILITY_MODE, "false");
+        properties.put(Constants.SERVLET_PARAMETER_PRODUCTION_MODE, "true");
+        properties.put(Constants.SERVLET_PARAMETER_ENABLE_DEV_SERVER, "false");
+
+        Mockito.when(servletConfig.getInitParameterNames())
+                .thenReturn(Collections.enumeration(properties.keySet()));
+        Mockito.when(servletConfig.getInitParameter(Mockito.anyString()))
+                .then(invocation -> properties
+                        .get(invocation.getArguments()[0]));
+        config = new VaadinServletConfig(servletConfig);
+    }
+
+    @Test
+    public void getPropertyNames_returnsExpectedProperties() {
+        List list = Collections.list(config.getConfigParameterNames());
+        Assert.assertEquals(
+                "Context should return only keys defined in ServletContext",
+                properties.size(), list.size());
+        for (String key : properties.keySet()) {
+            Assert.assertEquals(String.format(
+                    "Value should be same from context for key '%s'", key),
+                    properties.get(key), config.getConfigParameter(key));
+        }
+    }
+
+
+    @Test
+    public void vaadinContextThroughConfig_setAndGetAttribute() {
+        String value = "my-attribute";
+        config.getVaadinContext().setAttribute(value);
+        String result = config.getVaadinContext().getAttribute(String.class);
+        Assert.assertEquals(value, result);
+        // overwrite
+        String newValue = "this is a new value";
+        config.getVaadinContext().setAttribute(newValue);
+        result = config.getVaadinContext().getAttribute(String.class);
+        Assert.assertEquals(newValue, result);
+        // now the provider should not be called, so value should be still there
+        result = config.getVaadinContext().getAttribute(String.class,
+                () -> {
+                    throw new AssertionError("Should not be called");
+                });
+        Assert.assertEquals(newValue, result);
+    }
+}
diff --git a/flow-server/src/test/java/com/vaadin/flow/server/VaadinServletContextTest.java b/flow-server/src/test/java/com/vaadin/flow/server/VaadinServletContextTest.java
index 3c17bd9aa4d..be54db257aa 100644
--- a/flow-server/src/test/java/com/vaadin/flow/server/VaadinServletContextTest.java
+++ b/flow-server/src/test/java/com/vaadin/flow/server/VaadinServletContextTest.java
@@ -1,17 +1,20 @@
 package com.vaadin.flow.server;
 
+import javax.servlet.ServletContext;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
 import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Test;
 import org.mockito.Mockito;
 
-import javax.servlet.ServletContext;
-import java.util.HashMap;
-import java.util.Map;
-
 /**
- * @author miki
- * @since 2019-05-27
+ * Tests for VaadinServletContext attribute storage and property delegation.
+ *
+ * @since 2.0.0
  */
 public class VaadinServletContextTest {
     
@@ -22,6 +25,7 @@ private static String testAttributeProvider() {
     private VaadinServletContext context;
     
     private final Map attributeMap = new HashMap<>();
+    private Map properties;
 
     @Before
     public void setup() {
@@ -31,7 +35,17 @@ public void setup() {
             invocationOnMock.getArguments()[0].toString(),
             invocationOnMock.getArguments()[1]
             )).when(servletContext).setAttribute(Mockito.anyString(), Mockito.any());
-        
+
+        properties = new HashMap<>();
+        properties.put(Constants.SERVLET_PARAMETER_COMPATIBILITY_MODE, "false");
+        properties.put(Constants.SERVLET_PARAMETER_PRODUCTION_MODE, "true");
+        properties.put(Constants.SERVLET_PARAMETER_ENABLE_DEV_SERVER, "false");
+
+        Mockito.when(servletContext.getInitParameterNames())
+                .thenReturn(Collections.enumeration(properties.keySet()));
+        Mockito.when(servletContext.getInitParameter(Mockito.anyString()))
+                .then(invocation -> properties
+                        .get(invocation.getArguments()[0]));
         context = new VaadinServletContext(servletContext);
     }
 
@@ -76,4 +90,17 @@ public void setAndGetAttribute() {
             });
         Assert.assertEquals(newValue, result);
     }
+
+    @Test
+    public void getPropertyNames_returnsExpectedProperties() {
+        List list = Collections.list(context.getContextParameterNames());
+        Assert.assertEquals(
+                "Context should return only keys defined in ServletContext",
+                properties.size(), list.size());
+        for (String key : properties.keySet()) {
+            Assert.assertEquals(String.format(
+                    "Value should be same from context for key '%s'", key),
+                    properties.get(key), context.getContextParameter(key));
+        }
+    }
 }
diff --git a/flow-server/src/test/java/com/vaadin/flow/server/communication/CommunicationUtil.java b/flow-server/src/test/java/com/vaadin/flow/server/communication/CommunicationUtil.java
new file mode 100644
index 00000000000..22dc134e149
--- /dev/null
+++ b/flow-server/src/test/java/com/vaadin/flow/server/communication/CommunicationUtil.java
@@ -0,0 +1,77 @@
+/*
+ * Copyright 2000-2019 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ *
+ */
+
+package com.vaadin.flow.server.communication;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.io.PrintWriter;
+import java.util.List;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.stream.Collectors;
+
+import org.mockito.ArgumentCaptor;
+import org.mockito.Mockito;
+import org.mockito.internal.verification.VerificationModeFactory;
+
+class CommunicationUtil {
+
+    static String getStringWhenWriteBytesOffsetLength(OutputStream outputStream)
+            throws IOException {
+        ArgumentCaptor contentArg = ArgumentCaptor
+                .forClass(byte[].class);
+        ArgumentCaptor offsetArg = ArgumentCaptor.forClass(int.class);
+        ArgumentCaptor lengthArg = ArgumentCaptor.forClass(int.class);
+
+        Mockito.verify(outputStream, VerificationModeFactory.atLeastOnce())
+                .write(contentArg.capture(), offsetArg.capture(),
+                        lengthArg.capture());
+
+        List offsetValues = offsetArg.getAllValues();
+        List lengthValues = lengthArg.getAllValues();
+
+        AtomicInteger i = new AtomicInteger();
+
+        return contentArg.getAllValues().stream().map(bytes -> {
+            return new String(bytes, offsetValues.get(i.get()),
+                    lengthValues.get(i.getAndIncrement()));
+        }).collect(Collectors.joining());
+    }
+
+    static String getStringWhenWriteString(OutputStream outputStream)
+            throws IOException {
+        ArgumentCaptor contentArg = ArgumentCaptor
+                .forClass(byte[].class);
+
+        Mockito.verify(outputStream, VerificationModeFactory.atLeastOnce())
+                .write(contentArg.capture());
+
+        return contentArg.getAllValues().stream()
+                .map(bytes -> new String(bytes)).collect(Collectors.joining());
+    }
+
+    static String getStringWhenWriteString(PrintWriter printWriter) {
+        ArgumentCaptor contentArg = ArgumentCaptor
+                .forClass(String.class);
+
+        Mockito.verify(printWriter, VerificationModeFactory.atLeastOnce())
+                .write(contentArg.capture());
+
+        return String.join("", contentArg.getAllValues());
+    }
+
+}
diff --git a/flow-server/src/test/java/com/vaadin/flow/server/communication/MetadataWriterTest.java b/flow-server/src/test/java/com/vaadin/flow/server/communication/MetadataWriterTest.java
index 3be9e8c822d..ee1ccfee959 100644
--- a/flow-server/src/test/java/com/vaadin/flow/server/communication/MetadataWriterTest.java
+++ b/flow-server/src/test/java/com/vaadin/flow/server/communication/MetadataWriterTest.java
@@ -15,9 +15,6 @@
  */
 package com.vaadin.flow.server.communication;
 
-import static org.mockito.Mockito.mock;
-import static org.mockito.Mockito.when;
-
 import java.io.IOException;
 
 import org.junit.Assert;
@@ -28,11 +25,14 @@
 import com.vaadin.flow.component.UI;
 import com.vaadin.flow.server.SystemMessages;
 import com.vaadin.flow.server.VaadinSession;
+import com.vaadin.flow.server.VaadinSessionState;
 import com.vaadin.flow.server.WrappedSession;
-import com.vaadin.flow.server.communication.MetadataWriter;
 
 import elemental.json.JsonObject;
 
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
 public class MetadataWriterTest {
 
     private UI ui;
@@ -55,33 +55,25 @@ private void disableSessionExpirationMessages(SystemMessages messages) {
 
     @Test
     public void writeAsyncTag() throws Exception {
-        JsonObject meta = new MetadataWriter().createMetadata(ui, false, true,
-                messages);
-        Assert.assertEquals("{\"async\":true}", meta.toJson());
+        assertMetadataOutput(false, true, "{\"async\":true}");
     }
 
     @Test
     public void writeRepaintTag() throws Exception {
-        JsonObject meta = new MetadataWriter().createMetadata(ui, true, false,
-                messages);
-        Assert.assertEquals("{\"repaintAll\":true}", meta.toJson());
+        assertMetadataOutput(true, false, "{\"repaintAll\":true}");
     }
 
     @Test
     public void writeRepaintAndAsyncTag() throws Exception {
-        JsonObject meta = new MetadataWriter().createMetadata(ui, true, true,
-                messages);
-        Assert.assertEquals("{\"repaintAll\":true,\"async\":true}",
-                meta.toJson());
+        assertMetadataOutput(true, true,
+                "{\"repaintAll\":true,\"async\":true}");
     }
 
     @Test
     public void writeRedirectWithExpiredSession() throws Exception {
         disableSessionExpirationMessages(messages);
 
-        JsonObject meta = new MetadataWriter().createMetadata(ui, false, false,
-                messages);
-        Assert.assertEquals("{}", meta.toJson());
+        assertMetadataOutput(false, false, "{}");
     }
 
     @Test
@@ -91,11 +83,8 @@ public void writeRedirectWithActiveSession() throws Exception {
 
         disableSessionExpirationMessages(messages);
 
-        JsonObject meta = new MetadataWriter().createMetadata(ui, false, false,
-                messages);
-        Assert.assertEquals(
-                "{\"timedRedirect\":{\"interval\":15,\"url\":\"\"}}",
-                meta.toJson());
+        assertMetadataOutput(false, false,
+                "{\"timedRedirect\":{\"interval\":15,\"url\":\"\"}}");
     }
 
     @Test
@@ -105,10 +94,36 @@ public void writeAsyncWithSystemMessages() throws IOException {
 
         disableSessionExpirationMessages(messages);
 
-        JsonObject meta = new MetadataWriter().createMetadata(ui, false, true,
-                messages);
-        Assert.assertEquals(
-                "{\"async\":true,\"timedRedirect\":{\"interval\":15,\"url\":\"\"}}",
-                meta.toJson());
+        assertMetadataOutput(false, true,
+                "{\"async\":true,\"timedRedirect\":{\"interval\":15,\"url\":\"\"}}");
     }
+
+    @Test
+    public void writeSessionExpiredTag_sessionIsOpen() throws Exception {
+        Mockito.when(session.getState()).thenReturn(VaadinSessionState.OPEN);
+        assertMetadataOutput(false, false, "{}");
+    }
+
+    @Test
+    public void writeSessionExpiredTag_sessionIsClosing() throws Exception {
+        Mockito.when(session.getState()).thenReturn(VaadinSessionState.CLOSING);
+        assertMetadataOutput(false, false, "{\"sessionExpired\":true}");
+
+        Mockito.when(session.getState()).thenReturn(VaadinSessionState.CLOSED);
+        assertMetadataOutput(false, false, "{\"sessionExpired\":true}");
+    }
+
+    @Test
+    public void writeSessionExpiredTag_sessionIsClosed() throws Exception {
+        Mockito.when(session.getState()).thenReturn(VaadinSessionState.CLOSED);
+        assertMetadataOutput(false, false, "{\"sessionExpired\":true}");
+    }
+
+    private void assertMetadataOutput(boolean repaintAll, boolean async,
+            String expectedOutput) {
+        JsonObject meta = new MetadataWriter().createMetadata(ui, repaintAll,
+                async, messages);
+        Assert.assertEquals(expectedOutput, meta.toJson());
+    }
+
 }
diff --git a/flow-server/src/test/java/com/vaadin/flow/server/communication/PushAtmosphereHandlerTest.java b/flow-server/src/test/java/com/vaadin/flow/server/communication/PushAtmosphereHandlerTest.java
new file mode 100644
index 00000000000..135163a5817
--- /dev/null
+++ b/flow-server/src/test/java/com/vaadin/flow/server/communication/PushAtmosphereHandlerTest.java
@@ -0,0 +1,89 @@
+/*
+ * Copyright 2000-2019 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ *
+ */
+
+package com.vaadin.flow.server.communication;
+
+import java.io.IOException;
+import java.io.PrintWriter;
+import java.util.Properties;
+
+import com.vaadin.flow.server.DefaultDeploymentConfiguration;
+import com.vaadin.flow.server.VaadinServletService;
+import org.atmosphere.cpr.AtmosphereRequest;
+import org.atmosphere.cpr.AtmosphereResource;
+import org.atmosphere.cpr.AtmosphereResponse;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+import org.mockito.Mockito;
+
+public class PushAtmosphereHandlerTest {
+
+    private AtmosphereResource resource;
+
+    private AtmosphereRequest request;
+    private AtmosphereResponse response;
+    private PrintWriter printWriter;
+
+    private PushAtmosphereHandler atmosphereHandler;
+
+    @Before
+    public void setup() throws IOException {
+        request = Mockito.mock(AtmosphereRequest.class);
+        response = Mockito.mock(AtmosphereResponse.class);
+        printWriter = Mockito.mock(PrintWriter.class);
+        Mockito.when(response.getWriter()).thenReturn(printWriter);
+
+        resource = Mockito.mock(AtmosphereResource.class);
+        Mockito.when(resource.getRequest()).thenReturn(request);
+        Mockito.when(resource.getResponse()).thenReturn(response);
+
+        VaadinServletService service = new VaadinServletService(null,
+                new DefaultDeploymentConfiguration(getClass(),
+                        new Properties()));
+
+        PushHandler handler = new PushHandler(service);
+
+        atmosphereHandler = new PushAtmosphereHandler();
+        atmosphereHandler.setPushHandler(handler);
+    }
+
+    @Test
+    public void writeSessionExpiredAsyncGet() throws Exception {
+        writeSessionExpiredAsync("GET");
+    }
+
+    @Test
+    public void writeSessionExpiredAsyncPost() throws Exception {
+        writeSessionExpiredAsync("POST");
+    }
+
+    private void writeSessionExpiredAsync(String httpMethod) throws IOException {
+        Mockito.when(request.getMethod()).thenReturn(httpMethod);
+
+        atmosphereHandler.onRequest(resource);
+
+        String responseContent = CommunicationUtil
+                .getStringWhenWriteString(printWriter);
+
+        // response shouldn't contain async
+        Assert.assertEquals("Invalid response",
+                "for(;;);[{\"meta\":{\"async\":true,\"sessionExpired\":true}}]",
+                responseContent);
+    }
+
+}
diff --git a/flow-server/src/test/java/com/vaadin/flow/server/communication/ServerRpcHandlerTest.java b/flow-server/src/test/java/com/vaadin/flow/server/communication/ServerRpcHandlerTest.java
new file mode 100644
index 00000000000..ab22e580fa3
--- /dev/null
+++ b/flow-server/src/test/java/com/vaadin/flow/server/communication/ServerRpcHandlerTest.java
@@ -0,0 +1,78 @@
+package com.vaadin.flow.server.communication;
+
+import java.io.IOException;
+import java.io.StringReader;
+
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+import org.mockito.Mockito;
+
+import com.vaadin.flow.component.UI;
+import com.vaadin.flow.component.internal.UIInternals;
+import com.vaadin.flow.function.DeploymentConfiguration;
+import com.vaadin.flow.internal.StateTree;
+import com.vaadin.flow.server.VaadinRequest;
+import com.vaadin.flow.server.VaadinService;
+import com.vaadin.flow.server.VaadinSession;
+
+public class ServerRpcHandlerTest {
+    private VaadinRequest request;
+    private VaadinService service;
+    private VaadinSession session;
+    private UI ui;
+    private UIInternals uiInternals;
+    private StateTree uiTree;
+    final private String csrfToken = "";
+
+    private ServerRpcHandler serverRpcHandler;
+
+    @Rule
+    public ExpectedException thrown = ExpectedException.none();
+
+    @Before
+    public void setup() {
+        request = Mockito.mock(VaadinRequest.class);
+        service = Mockito.mock(VaadinService.class);
+        session = Mockito.mock(VaadinSession.class);
+        ui = Mockito.mock(UI.class);
+        uiInternals = Mockito.mock(UIInternals.class);
+
+        Mockito.when(request.getService()).thenReturn(service);
+        Mockito.when(session.getService()).thenReturn(service);
+
+        Mockito.when(ui.getInternals()).thenReturn(uiInternals);
+        Mockito.when(ui.getSession()).thenReturn(session);
+        Mockito.when(ui.getCsrfToken()).thenReturn(csrfToken);
+
+        DeploymentConfiguration deploymentConfiguration = Mockito
+                .mock(DeploymentConfiguration.class);
+        Mockito.when(service.getDeploymentConfiguration())
+                .thenReturn(deploymentConfiguration);
+
+        uiTree = new StateTree(uiInternals);
+        Mockito.when(uiInternals.getStateTree()).thenReturn(uiTree);
+
+        serverRpcHandler = new ServerRpcHandler();
+    }
+
+    @Test
+    public void handleRpc_resynchronize_shouldResynchronizeClientAndMarksTreeDirty()
+            throws IOException,
+            ServerRpcHandler.InvalidUIDLSecurityKeyException {
+        // given
+        StringReader reader = new StringReader("{\"csrfToken\": \"" + csrfToken
+                + "\", \"rpc\":[], \"resynchronize\": true, \"clientId\":1}");
+        uiTree.collectChanges(c -> { // clean tree
+        });
+        thrown.expect(ServerRpcHandler.ResynchronizationRequiredException.class);
+
+        // when
+        serverRpcHandler.handleRpc(ui, reader, request);
+
+        // then
+        Assert.assertTrue(uiTree.hasDirtyNodes());
+    }
+}
diff --git a/flow-server/src/test/java/com/vaadin/flow/server/communication/UidlRequestHandlerTest.java b/flow-server/src/test/java/com/vaadin/flow/server/communication/UidlRequestHandlerTest.java
new file mode 100644
index 00000000000..87d09a34b68
--- /dev/null
+++ b/flow-server/src/test/java/com/vaadin/flow/server/communication/UidlRequestHandlerTest.java
@@ -0,0 +1,101 @@
+/*
+ * Copyright 2000-2019 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ *
+ */
+
+package com.vaadin.flow.server.communication;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.util.Properties;
+
+import com.vaadin.flow.server.DefaultDeploymentConfiguration;
+import com.vaadin.flow.server.ServletHelper.RequestType;
+import com.vaadin.flow.server.VaadinRequest;
+import com.vaadin.flow.server.VaadinResponse;
+import com.vaadin.flow.server.VaadinService;
+import com.vaadin.flow.server.VaadinServletService;
+import com.vaadin.flow.server.VaadinSession;
+import com.vaadin.flow.shared.ApplicationConstants;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+import org.mockito.Mockito;
+
+public class UidlRequestHandlerTest {
+
+    private VaadinRequest request;
+    private VaadinResponse response;
+    private OutputStream outputStream;
+
+    private UidlRequestHandler handler;
+
+    @Before
+    public void setup() throws IOException {
+        request = Mockito.mock(VaadinRequest.class);
+        response = Mockito.mock(VaadinResponse.class);
+        outputStream = Mockito.mock(OutputStream.class);
+        Mockito.when(response.getOutputStream()).thenReturn(outputStream);
+
+        handler = new UidlRequestHandler();
+    }
+
+    @Test
+    public void writeSessionExpired() throws Exception {
+
+        VaadinService service = new VaadinServletService(null,
+                new DefaultDeploymentConfiguration(getClass(),
+                        new Properties()));
+        Mockito.when(request.getService()).thenReturn(service);
+
+        Mockito.when(request
+                .getParameter(ApplicationConstants.REQUEST_TYPE_PARAMETER))
+                .thenReturn(RequestType.UIDL.getIdentifier());
+
+        boolean result = handler.handleSessionExpired(request, response);
+        Assert.assertTrue("Result should be true", result);
+
+        String responseContent = CommunicationUtil
+                .getStringWhenWriteBytesOffsetLength(outputStream);
+
+        // response shouldn't contain async
+        Assert.assertEquals("Invalid response",
+                "for(;;);[{\"meta\":{\"sessionExpired\":true}}]",
+                responseContent);
+    }
+
+    @Test
+    public void writeSessionExpired_whenUINotFound() throws IOException {
+
+        VaadinService service = Mockito.mock(VaadinService.class);
+        VaadinSession session = Mockito.mock(VaadinSession.class);
+        Mockito.when(session.getService()).thenReturn(service);
+
+        Mockito.when(service.findUI(request)).thenReturn(null);
+
+        boolean result = handler.synchronizedHandleRequest(session, request,
+                response);
+        Assert.assertTrue("Result should be true", result);
+
+        String responseContent = CommunicationUtil
+                .getStringWhenWriteString(outputStream);
+
+        // response shouldn't contain async
+        Assert.assertEquals("Invalid response",
+                "for(;;);[{\"meta\":{\"sessionExpired\":true}}]",
+                responseContent);
+    }
+
+}
diff --git a/flow-server/src/test/java/com/vaadin/flow/server/communication/UidlWriterTest.java b/flow-server/src/test/java/com/vaadin/flow/server/communication/UidlWriterTest.java
index c40f294508b..e10218e892d 100644
--- a/flow-server/src/test/java/com/vaadin/flow/server/communication/UidlWriterTest.java
+++ b/flow-server/src/test/java/com/vaadin/flow/server/communication/UidlWriterTest.java
@@ -352,6 +352,19 @@ public void parentViewDependenciesAreAddedFirst_npmMode() throws Exception {
         }
     }
 
+    @Test
+    public void resynchronizationRequested_responseFieldContainsResynchronize()
+            throws Exception {
+        UI ui = initializeUIForDependenciesTest(new TestUI());
+        UidlWriter uidlWriter = new UidlWriter();
+
+        JsonObject response = uidlWriter.createUidl(ui, false, true);
+        assertTrue("Response contains resynchronize field",
+                response.hasKey(ApplicationConstants.RESYNCHRONIZE_ID));
+        assertTrue("Response resynchronize field is set to true",
+               response.getBoolean(ApplicationConstants.RESYNCHRONIZE_ID));
+    }
+
     private void assertInlineDependencies(List inlineDependencies,
             String expectedPrefix) {
         assertThat("Should have an inline dependency", inlineDependencies,
diff --git a/flow-server/src/test/java/com/vaadin/flow/server/communication/WebComponentBootstrapHandlerTest.java b/flow-server/src/test/java/com/vaadin/flow/server/communication/WebComponentBootstrapHandlerTest.java
new file mode 100644
index 00000000000..859f899dd4b
--- /dev/null
+++ b/flow-server/src/test/java/com/vaadin/flow/server/communication/WebComponentBootstrapHandlerTest.java
@@ -0,0 +1,66 @@
+/*
+ * Copyright 2000-2018 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.flow.server.communication;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+
+import org.hamcrest.CoreMatchers;
+import org.jsoup.nodes.Document;
+import org.jsoup.nodes.Element;
+import org.junit.Assert;
+import org.junit.Test;
+import org.mockito.Mockito;
+
+import com.vaadin.flow.server.VaadinResponse;
+
+public class WebComponentBootstrapHandlerTest {
+
+    @Test
+    public void writeBootstrapPage_skipMetaAndStyleHeaderElements()
+            throws IOException {
+        WebComponentBootstrapHandler handler = new WebComponentBootstrapHandler();
+
+        ByteArrayOutputStream stream = new ByteArrayOutputStream();
+
+        Element head = new Document("").normalise().head();
+        Element meta = head.ownerDocument().createElement("meta");
+        head.appendChild(meta);
+        meta.attr("http-equiv", "Content-Type");
+
+        Element style = head.ownerDocument().createElement("style");
+        head.appendChild(style);
+        style.attr("type'", "text/css");
+        style.text("body {height:100vh;width:100vw;margin:0;}");
+
+        Element script = head.ownerDocument().createElement("script");
+        head.appendChild(script);
+        script.text("var i=1;");
+
+        VaadinResponse response = Mockito.mock(VaadinResponse.class);
+        Mockito.when(response.getOutputStream()).thenReturn(stream);
+        handler.writeBootstrapPage("", response, head, "");
+
+        String resultingScript = stream.toString();
+
+        Assert.assertThat(resultingScript,
+                CoreMatchers.containsString("var i=1;"));
+        Assert.assertThat(resultingScript, CoreMatchers.not(CoreMatchers
+                .containsString("body {height:100vh;width:100vw;margin:0;}")));
+        Assert.assertThat(resultingScript,
+                CoreMatchers.not(CoreMatchers.containsString("http-equiv")));
+    }
+}
diff --git a/flow-server/src/test/java/com/vaadin/flow/server/communication/rpc/PublishedServerEventHandlerRpcHandlerTest.java b/flow-server/src/test/java/com/vaadin/flow/server/communication/rpc/PublishedServerEventHandlerRpcHandlerTest.java
index 3d1301577c0..4c149cc6a98 100644
--- a/flow-server/src/test/java/com/vaadin/flow/server/communication/rpc/PublishedServerEventHandlerRpcHandlerTest.java
+++ b/flow-server/src/test/java/com/vaadin/flow/server/communication/rpc/PublishedServerEventHandlerRpcHandlerTest.java
@@ -15,6 +15,8 @@
  */
 package com.vaadin.flow.server.communication.rpc;
 
+import java.util.List;
+
 import net.jcip.annotations.NotThreadSafe;
 import org.jsoup.nodes.Element;
 import org.junit.After;
@@ -29,6 +31,8 @@
 import com.vaadin.flow.component.EventData;
 import com.vaadin.flow.component.Tag;
 import com.vaadin.flow.component.UI;
+import com.vaadin.flow.component.internal.PendingJavaScriptInvocation;
+import com.vaadin.flow.component.internal.UIInternals.JavaScriptInvocation;
 import com.vaadin.flow.component.polymertemplate.EventHandler;
 import com.vaadin.flow.component.polymertemplate.PolymerTemplate;
 import com.vaadin.flow.component.polymertemplate.TemplateParser.TemplateData;
@@ -37,6 +41,7 @@
 import com.vaadin.flow.server.VaadinService;
 import com.vaadin.flow.shared.JsonConstants;
 import com.vaadin.flow.templatemodel.TemplateModel;
+import com.vaadin.tests.util.MockUI;
 
 import elemental.json.Json;
 import elemental.json.JsonArray;
@@ -67,6 +72,15 @@ private void method() {
             isInvoked = true;
         }
 
+        @ClientCallable
+        private int compute(int input) {
+            if (input < 0) {
+                throw new ArithmeticException();
+            } else {
+                return (int) Math.sqrt(input);
+            }
+        }
+
     }
 
     @Tag(Tag.DIV)
@@ -221,7 +235,7 @@ public void tearDown() {
     public void methodIsInvoked() {
         ComponentWithMethod component = new ComponentWithMethod();
         PublishedServerEventHandlerRpcHandler.invokeMethod(component,
-                component.getClass(), "method", Json.createArray());
+                component.getClass(), "method", Json.createArray(), -1);
 
         Assert.assertTrue(component.isInvoked);
     }
@@ -231,7 +245,7 @@ public void methodIsInvokedOnCompositeContent() {
         CompositeOfComponentWithMethod composite = new CompositeOfComponentWithMethod();
         ComponentWithMethod component = composite.getContent();
         PublishedServerEventHandlerRpcHandler.invokeMethod(composite,
-                composite.getClass(), "method", Json.createArray());
+                composite.getClass(), "method", Json.createArray(), -1);
 
         Assert.assertTrue(component.isInvoked);
     }
@@ -241,7 +255,7 @@ public void methodIsInvokectOnCompositeOfComposite() {
         CompositeOfComposite composite = new CompositeOfComposite();
         ComponentWithMethod component = composite.getContent().getContent();
         PublishedServerEventHandlerRpcHandler.invokeMethod(composite,
-                composite.getClass(), "method", Json.createArray());
+                composite.getClass(), "method", Json.createArray(), -1);
 
         Assert.assertTrue(component.isInvoked);
     }
@@ -254,7 +268,7 @@ public void methodWithDecoderParameters_convertableValues_methodIsInvoked() {
 
         DecoderParameters component = new DecoderParameters();
         PublishedServerEventHandlerRpcHandler.invokeMethod(component,
-                component.getClass(), "method", params);
+                component.getClass(), "method", params, -1);
 
         Assert.assertTrue(component.isInvoked);
     }
@@ -267,7 +281,7 @@ public void methodWithDecoderParameters_nonConvertableValues_methodIsInvoked() {
 
         DecoderParameters component = new DecoderParameters();
         PublishedServerEventHandlerRpcHandler.invokeMethod(component,
-                component.getClass(), "method", params);
+                component.getClass(), "method", params, -1);
     }
 
     @Test(expected = IllegalArgumentException.class)
@@ -276,21 +290,105 @@ public void methodWithoutArgs_argsProvided() {
         args.set(0, true);
         ComponentWithMethod component = new ComponentWithMethod();
         PublishedServerEventHandlerRpcHandler.invokeMethod(component,
-                component.getClass(), "method", args);
+                component.getClass(), "method", args, -1);
+    }
+
+    @Test
+    public void promiseSuccess() {
+        int promiseId = 4;
+
+        JsonArray args = Json.createArray();
+        args.set(0, 36);
+
+        ComponentWithMethod component = new ComponentWithMethod();
+        MockUI ui = new MockUI();
+        ui.add(component);
+
+        // Get rid of attach invocations
+        ui.getInternals().getStateTree().runExecutionsBeforeClientResponse();
+        ui.getInternals().dumpPendingJavaScriptInvocations();
+
+        PublishedServerEventHandlerRpcHandler.invokeMethod(component,
+                component.getClass(), "compute", args, promiseId);
+
+        List pendingJavaScriptInvocations = ui
+                .dumpPendingJsInvocations();
+        Assert.assertEquals(1, pendingJavaScriptInvocations.size());
+
+        JavaScriptInvocation invocation = pendingJavaScriptInvocations.get(0)
+                .getInvocation();
+        Assert.assertTrue("Invocation does not look like a promise callback",
+                invocation.getExpression()
+                        .contains(JsonConstants.RPC_PROMISE_CALLBACK_NAME));
+
+        List parameters = invocation.getParameters();
+        Assert.assertEquals(
+                "Expected three paramters: promiseId, value, target", 3,
+                parameters.size());
+        Assert.assertEquals(
+                "Promise id should match the value passed to invokeMethod",
+                Integer.valueOf(promiseId), parameters.get(0));
+        Assert.assertEquals("Promise value should be sqrt(36) = 6",
+                Integer.valueOf(6), parameters.get(1));
+        Assert.assertEquals("Target should be the component's element",
+                component.getElement(), parameters.get(2));
+    }
+
+    @Test
+    public void promiseFailure() {
+        int promiseId = 4;
+
+        JsonArray args = Json.createArray();
+        args.set(0, -36);
+
+        ComponentWithMethod component = new ComponentWithMethod();
+        MockUI ui = new MockUI();
+        ui.add(component);
+
+        // Get rid of attach invocations
+        ui.getInternals().getStateTree().runExecutionsBeforeClientResponse();
+        ui.getInternals().dumpPendingJavaScriptInvocations();
+
+        try {
+            PublishedServerEventHandlerRpcHandler.invokeMethod(component,
+                    component.getClass(), "compute", args, promiseId);
+            Assert.fail("Exception should be thrown");
+        } catch (RuntimeException e) {
+            Assert.assertTrue(e.getCause() instanceof ArithmeticException);
+        }
+
+        List pendingJavaScriptInvocations = ui
+                .dumpPendingJsInvocations();
+        Assert.assertEquals(1, pendingJavaScriptInvocations.size());
+
+        JavaScriptInvocation invocation = pendingJavaScriptInvocations.get(0)
+                .getInvocation();
+        Assert.assertTrue("Invocation does not look like a promise callback",
+                invocation.getExpression()
+                        .contains(JsonConstants.RPC_PROMISE_CALLBACK_NAME));
+
+        List parameters = invocation.getParameters();
+        Assert.assertEquals("Expected two paramters: promiseId,  target", 2,
+                parameters.size());
+        Assert.assertEquals(
+                "Promise id should match the value passed to invokeMethod",
+                Integer.valueOf(promiseId), parameters.get(0));
+        Assert.assertEquals("Target should be the component's element",
+                component.getElement(), parameters.get(1));
     }
 
     @Test(expected = IllegalStateException.class)
     public void twoEventHandlerMethodsWithTheSameName() {
         ComponentWithTwoEventHandlerMethodSameName component = new ComponentWithTwoEventHandlerMethodSameName();
         PublishedServerEventHandlerRpcHandler.invokeMethod(component,
-                component.getClass(), "intMethod", Json.createArray());
+                component.getClass(), "intMethod", Json.createArray(), -1);
     }
 
     @Test(expected = IllegalArgumentException.class)
     public void methodWithParametersInvokedWithoutParameters() {
         MethodWithParameters component = new MethodWithParameters();
         PublishedServerEventHandlerRpcHandler.invokeMethod(component,
-                component.getClass(), "intMethod", Json.createArray());
+                component.getClass(), "intMethod", Json.createArray(), -1);
     }
 
     @Test
@@ -299,7 +397,7 @@ public void methodWithParameterInvokedWithProperParameter() {
         array.set(0, 65);
         MethodWithParameters component = new MethodWithParameters();
         PublishedServerEventHandlerRpcHandler.invokeMethod(component,
-                component.getClass(), "intMethod", array);
+                component.getClass(), "intMethod", array, -1);
 
         Assert.assertEquals(65, component.intArg);
     }
@@ -314,7 +412,7 @@ public void methodWithArrayParamIsInvoked() {
         array.set(1, secondArg);
         MethodWithParameters component = new MethodWithParameters();
         PublishedServerEventHandlerRpcHandler.invokeMethod(component,
-                component.getClass(), "method1", array);
+                component.getClass(), "method1", array, -1);
 
         Assert.assertEquals("foo", component.strArg);
         Assert.assertArrayEquals(new boolean[] { true, false },
@@ -336,7 +434,7 @@ public void methodWithVarArgIsInvoked_varArgsAreNotArray() {
 
         MethodWithParameters component = new MethodWithParameters();
         PublishedServerEventHandlerRpcHandler.invokeMethod(component,
-                component.getClass(), "method2", array);
+                component.getClass(), "method2", array, -1);
 
         Assert.assertArrayEquals(
                 new Double[] { firstArg.getNumber(0), firstArg.getNumber(1) },
@@ -370,7 +468,7 @@ public void methodWithDoubleArrayIsInvoked() {
 
         MethodWithParameters component = new MethodWithParameters();
         PublishedServerEventHandlerRpcHandler.invokeMethod(component,
-                component.getClass(), "method3", array);
+                component.getClass(), "method3", array, -1);
 
         Assert.assertArrayEquals(new int[] { (int) first.getNumber(0),
                 (int) first.getNumber(1) }, component.doubleArray[0]);
@@ -389,7 +487,7 @@ public void methodWithJsonValueIsInvoked() {
 
         MethodWithParameters component = new MethodWithParameters();
         PublishedServerEventHandlerRpcHandler.invokeMethod(component,
-                component.getClass(), "method4", array);
+                component.getClass(), "method4", array, -1);
 
         Assert.assertEquals(component.jsonValue, json);
     }
@@ -412,7 +510,7 @@ public void methodWithVarArgIsInvoked_varArgsIsArray() {
 
         MethodWithParameters component = new MethodWithParameters();
         PublishedServerEventHandlerRpcHandler.invokeMethod(component,
-                component.getClass(), "method2", array);
+                component.getClass(), "method2", array, -1);
 
         Assert.assertArrayEquals(
                 new Double[] { firstArg.getNumber(0), firstArg.getNumber(1) },
@@ -429,7 +527,7 @@ public void methodWithVarArg_acceptNoValues() {
 
         MethodWithVarArgParameter component = new MethodWithVarArgParameter();
         PublishedServerEventHandlerRpcHandler.invokeMethod(component,
-                component.getClass(), "varArgMethod", array);
+                component.getClass(), "varArgMethod", array, -1);
 
         Assert.assertEquals(0, component.varArg.length);
     }
@@ -446,7 +544,7 @@ public void methodWithSeveralArgsAndVarArg_acceptNoValues() {
 
         MethodWithParameters component = new MethodWithParameters();
         PublishedServerEventHandlerRpcHandler.invokeMethod(component,
-                component.getClass(), "method2", array);
+                component.getClass(), "method2", array, -1);
 
         Assert.assertArrayEquals(
                 new Double[] { firstArg.getNumber(0), firstArg.getNumber(1) },
@@ -464,7 +562,7 @@ public void methodWithVarArg_acceptOneValue() {
 
         MethodWithVarArgParameter component = new MethodWithVarArgParameter();
         PublishedServerEventHandlerRpcHandler.invokeMethod(component,
-                component.getClass(), "varArgMethod", array);
+                component.getClass(), "varArgMethod", array, -1);
 
         Assert.assertEquals(1, component.varArg.length);
         Assert.assertEquals("foo", component.varArg[0]);
@@ -480,7 +578,7 @@ public void methodWithVarArg_arrayIsCorrectlyHandled() {
 
         MethodWithVarArgParameter component = new MethodWithVarArgParameter();
         PublishedServerEventHandlerRpcHandler.invokeMethod(component,
-                component.getClass(), "varArgMethod", array);
+                component.getClass(), "varArgMethod", array, -1);
 
         Assert.assertArrayEquals(new String[] { value.getString(0) },
                 component.varArg);
@@ -492,21 +590,21 @@ public void nullValueIsNotAcceptedForPrimitive() {
         array.set(0, Json.createNull());
         MethodWithParameters component = new MethodWithParameters();
         PublishedServerEventHandlerRpcHandler.invokeMethod(component,
-                component.getClass(), "method", array);
+                component.getClass(), "method", array, -1);
     }
 
     @Test(expected = IllegalStateException.class)
     public void noEventHandlerMethodException() {
         ComponentWithNoEventHandlerMethod component = new ComponentWithNoEventHandlerMethod();
         PublishedServerEventHandlerRpcHandler.invokeMethod(component,
-                component.getClass(), "operation", Json.createArray());
+                component.getClass(), "operation", Json.createArray(), -1);
     }
 
     @Test(expected = IllegalStateException.class)
     public void noMethodException() {
         ComponentWithNoEventHandlerMethod component = new ComponentWithNoEventHandlerMethod();
         PublishedServerEventHandlerRpcHandler.invokeMethod(component,
-                component.getClass(), "operation1", Json.createArray());
+                component.getClass(), "operation1", Json.createArray(), -1);
     }
 
     @Test
@@ -514,7 +612,7 @@ public void methodThrowsException_exceptionHasCorrectCause() {
         ComponentWithMethodThrowingException component = new ComponentWithMethodThrowingException();
         try {
             PublishedServerEventHandlerRpcHandler.invokeMethod(component,
-                    component.getClass(), "method", Json.createArray());
+                    component.getClass(), "method", Json.createArray(), -1);
         } catch (RuntimeException e) {
             Assert.assertTrue(e.getCause() instanceof NullPointerException);
         }
diff --git a/flow-server/src/test/java/com/vaadin/flow/server/frontend/AbstractNodeUpdatePackagesTest.java b/flow-server/src/test/java/com/vaadin/flow/server/frontend/AbstractNodeUpdatePackagesTest.java
index 48889ba780b..7de2a1c28f6 100644
--- a/flow-server/src/test/java/com/vaadin/flow/server/frontend/AbstractNodeUpdatePackagesTest.java
+++ b/flow-server/src/test/java/com/vaadin/flow/server/frontend/AbstractNodeUpdatePackagesTest.java
@@ -77,7 +77,7 @@ public void setup() throws Exception {
         NodeUpdateTestUtil.createStubNode(true, true,
                 baseDir.getAbsolutePath());
 
-        packageCreator = new TaskCreatePackageJson(baseDir, generatedDir);
+        packageCreator = new TaskCreatePackageJson(baseDir, generatedDir, null);
 
         ClassFinder classFinder = getClassFinder();
         packageUpdater = new TaskUpdatePackages(classFinder,
diff --git a/flow-server/src/test/java/com/vaadin/flow/server/frontend/AbstractUpdateImportsTest.java b/flow-server/src/test/java/com/vaadin/flow/server/frontend/AbstractUpdateImportsTest.java
index d66fbbe84e5..a6c68721337 100644
--- a/flow-server/src/test/java/com/vaadin/flow/server/frontend/AbstractUpdateImportsTest.java
+++ b/flow-server/src/test/java/com/vaadin/flow/server/frontend/AbstractUpdateImportsTest.java
@@ -18,8 +18,9 @@
 package com.vaadin.flow.server.frontend;
 
 import java.io.File;
-import java.io.IOException;
+import java.lang.annotation.Annotation;
 import java.lang.reflect.Method;
+import java.net.MalformedURLException;
 import java.net.URL;
 import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
@@ -27,6 +28,8 @@
 import java.util.Collection;
 import java.util.List;
 import java.util.Set;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 import org.apache.commons.io.FileUtils;
 import org.hamcrest.CoreMatchers;
@@ -43,6 +46,10 @@
 import org.slf4j.Logger;
 import org.slf4j.impl.SimpleLogger;
 
+import com.vaadin.flow.component.Component;
+import com.vaadin.flow.component.dependency.JavaScript;
+import com.vaadin.flow.component.dependency.JsModule;
+import com.vaadin.flow.router.Route;
 import com.vaadin.flow.server.Constants;
 import com.vaadin.flow.server.frontend.scanner.ClassFinder;
 import com.vaadin.flow.server.frontend.scanner.CssData;
@@ -55,6 +62,7 @@
 import static com.vaadin.flow.server.frontend.FrontendUtils.FLOW_NPM_PACKAGE_NAME;
 import static com.vaadin.flow.server.frontend.FrontendUtils.NODE_MODULES;
 import static org.hamcrest.MatcherAssert.assertThat;
+import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 
@@ -66,6 +74,7 @@ public abstract class AbstractUpdateImportsTest extends NodeUpdateTestUtil {
     @Rule
     public ExpectedException exception = ExpectedException.none();
 
+    private File tmpRoot;
     private File generatedPath;
     private File frontendDirectory;
     private File nodeModulesPath;
@@ -149,7 +158,7 @@ protected Logger getLogger() {
 
     @Before
     public void setup() throws Exception {
-        File tmpRoot = temporaryFolder.getRoot();
+        tmpRoot = temporaryFolder.getRoot();
 
         // Use a file for logs so as tests can assert the warnings shown to the
         // user.
@@ -377,7 +386,7 @@ public void cssFileNotFound_throws() {
     }
 
     @Test
-    public void generate_containsLumoThemeFiles() throws Exception {
+    public void generate_containsLumoThemeFiles() {
         updater.run();
 
         assertContainsImports(true, "@vaadin/vaadin-lumo-styles/color.js",
@@ -390,8 +399,7 @@ public void generate_containsLumoThemeFiles() throws Exception {
 
     // flow #6408
     @Test
-    public void jsModuleOnRouterLayout_shouldBe_addedAfterLumoStyles()
-            throws Exception {
+    public void jsModuleOnRouterLayout_shouldBe_addedAfterLumoStyles() {
         updater.run();
 
         assertContainsImports(true, "Frontend/common-js-file.js");
@@ -404,15 +412,70 @@ public void jsModuleOnRouterLayout_shouldBe_addedAfterLumoStyles()
     }
 
     @Test
-    public void jsModulesOrderIsPreservedAnsAfterJsModules() throws Exception {
+    public void jsModulesOrderIsPreservedAnsAfterJsModules() {
         updater.run();
 
         assertImportOrder("jsmodule/g.js", "javascript/a.js", "javascript/b.js",
                 "javascript/c.js");
     }
 
-    private void assertContainsImports(boolean contains, String... imports)
-            throws IOException {
+    @Route(value = "")
+    private static class MainView extends Component {
+        NodeTestComponents.TranslatedImports translatedImports;
+        NodeTestComponents.LocalP3Template localP3Template;
+        NodeTestComponents.JavaScriptOrder javaScriptOrder;
+    }
+
+    @Test
+    public void assertFullSortOrder() throws MalformedURLException {
+        Class[] testClasses = { MainView.class, NodeTestComponents.TranslatedImports.class,
+                NodeTestComponents.LocalP3Template.class,
+                NodeTestComponents.JavaScriptOrder.class };
+        ClassFinder classFinder = getClassFinder(testClasses);
+
+        updater = new UpdateImports(classFinder, getScanner(classFinder),
+                tmpRoot);
+        updater.run();
+
+        // Imports are collected as
+        // - theme and css
+        // - JsModules (external e.g. in node_modules/)
+        // - JavaScript
+        // - Generated webcompoents
+        // - JsModules (internal e.g. in frontend/)
+        List expectedImports = new ArrayList<>();
+        expectedImports.addAll(updater.getThemeLines());
+
+        getAnntotationsAsStream(JsModule.class, testClasses).map(JsModule::value).map(this::updateToImport).sorted().forEach(expectedImports::add);
+        getAnntotationsAsStream(JavaScript.class, testClasses).map(JavaScript::value).map(this::updateToImport).sorted().forEach(expectedImports::add);
+
+        List internals = expectedImports.stream().filter(importValue -> importValue.contains(FrontendUtils.WEBPACK_PREFIX_ALIAS)).sorted().collect(
+                Collectors.toList());
+        updater.getGeneratedModules().stream().map(this::updateToImport).forEach(expectedImports::add);
+        // Remove internals from the full list
+        expectedImports.removeAll(internals);
+        // Add internals to end of list
+        expectedImports.addAll(internals);
+
+        Assert.assertEquals(expectedImports, updater.resultingLines);
+    }
+
+    private  Stream getAnntotationsAsStream(Class annotation, Class... classes) {
+        Stream stream = Stream.empty();
+        for(Class clazz : classes) {
+            stream = Stream.concat(stream, Stream.of(clazz.getAnnotationsByType(annotation)));
+        }
+        return stream;
+    }
+
+    private String updateToImport(String value) {
+        if(value.startsWith("./")) {
+            value = value.replace("./", FrontendUtils.WEBPACK_PREFIX_ALIAS);
+        }
+        return String.format("import '%s';", value);
+    }
+
+    private void assertContainsImports(boolean contains, String... imports) {
         for (String line : imports) {
             boolean result = updater.resultingLines
                     .contains("import '" + addWebpackPrefix(line) + "';");
@@ -426,7 +489,7 @@ private void assertContainsImports(boolean contains, String... imports)
         }
     }
 
-    private void assertImportOrder(String... imports) throws IOException {
+    private void assertImportOrder(String... imports) {
         int curIndex = -1;
         for (String line : imports) {
             String prefixed = addWebpackPrefix(line);
diff --git a/flow-server/src/test/java/com/vaadin/flow/server/frontend/FrontendUtilsTest.java b/flow-server/src/test/java/com/vaadin/flow/server/frontend/FrontendUtilsTest.java
index 03213903aa0..6fa1f6931fa 100644
--- a/flow-server/src/test/java/com/vaadin/flow/server/frontend/FrontendUtilsTest.java
+++ b/flow-server/src/test/java/com/vaadin/flow/server/frontend/FrontendUtilsTest.java
@@ -113,12 +113,15 @@ public void should_useSystemNode() {
                 containsString("node"));
         assertThat(FrontendUtils.getNodeExecutable(baseDir),
                 not(containsString(DEFAULT_NODE)));
-        assertThat(FrontendUtils.getNpmExecutable(baseDir)
-                .get(0), containsString("npm"));
         assertThat(FrontendUtils.getNodeExecutable(baseDir),
                 not(containsString(NPM_CLI_STRING)));
-        assertEquals(1, FrontendUtils
+
+        assertEquals(2, FrontendUtils
                 .getNpmExecutable(baseDir).size());
+        assertThat(FrontendUtils.getNpmExecutable(baseDir)
+                .get(0), containsString("npm"));
+        assertThat(FrontendUtils.getNpmExecutable(baseDir)
+                .get(1), containsString("--no-update-notifier"));
     }
 
     @Test
diff --git a/flow-server/src/test/java/com/vaadin/flow/server/frontend/NodeUpdateTestUtil.java b/flow-server/src/test/java/com/vaadin/flow/server/frontend/NodeUpdateTestUtil.java
index aff02d044c9..e381b0ab691 100644
--- a/flow-server/src/test/java/com/vaadin/flow/server/frontend/NodeUpdateTestUtil.java
+++ b/flow-server/src/test/java/com/vaadin/flow/server/frontend/NodeUpdateTestUtil.java
@@ -45,6 +45,11 @@ static ClassFinder getClassFinder() throws MalformedURLException {
                 NodeTestComponents.class.getDeclaredClasses());
     }
 
+    static ClassFinder getClassFinder(Class... classes) throws MalformedURLException {
+        return new DefaultClassFinder(new URLClassLoader(getClassPath()),
+                classes);
+    }
+
     static URL[] getClassPath() throws MalformedURLException {
         // Add folder with test classes
         List classPaths = new ArrayList<>();
diff --git a/flow-server/src/test/java/com/vaadin/flow/server/frontend/NodeUpdaterTest.java b/flow-server/src/test/java/com/vaadin/flow/server/frontend/NodeUpdaterTest.java
index d50bc484360..f2c95d9866f 100644
--- a/flow-server/src/test/java/com/vaadin/flow/server/frontend/NodeUpdaterTest.java
+++ b/flow-server/src/test/java/com/vaadin/flow/server/frontend/NodeUpdaterTest.java
@@ -18,7 +18,6 @@
 import java.io.File;
 import java.io.IOException;
 import java.net.URL;
-import java.util.Arrays;
 import java.util.Set;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
@@ -33,6 +32,9 @@
 import com.vaadin.flow.server.frontend.scanner.ClassFinder;
 import com.vaadin.flow.server.frontend.scanner.FrontendDependencies;
 
+import elemental.json.Json;
+import elemental.json.JsonObject;
+
 import static com.vaadin.flow.server.Constants.COMPATIBILITY_RESOURCES_FRONTEND_DEFAULT;
 import static com.vaadin.flow.server.Constants.RESOURCES_FRONTEND_DEFAULT;
 
@@ -92,7 +94,8 @@ public void resolveResource_doesNotHaveModernResourcesFolder() {
     }
 
     @Test
-    public void getGeneratedModules_should_excludeByFileName() throws IOException {
+    public void getGeneratedModules_should_excludeByFileName()
+            throws IOException {
         File generated = temporaryFolder.newFolder();
         File fileA = new File(generated, "a.js");
         File fileB = new File(generated, "b.js");
@@ -100,15 +103,39 @@ public void getGeneratedModules_should_excludeByFileName() throws IOException {
         fileA.createNewFile();
         fileB.createNewFile();
         fileC.createNewFile();
-        
-        Set modules = NodeUpdater.getGeneratedModules(generated, Stream
-                .of("a.js", "/b.js").collect(Collectors.toSet()));
+
+        Set modules = NodeUpdater.getGeneratedModules(generated,
+                Stream.of("a.js", "/b.js").collect(Collectors.toSet()));
 
         Assert.assertEquals(1, modules.size());
         // GENERATED/ is an added prefix for files from this method
         Assert.assertTrue(modules.contains("GENERATED/c.js"));
     }
 
+    @Test
+    public void updateMainDefaultDependencies_polymerVersionIsNull_useDefault() {
+        JsonObject object = Json.createObject();
+        nodeUpdater.updateMainDefaultDependencies(object, null);
+
+        String version = getPolymerVersion(object);
+        Assert.assertEquals("3.2.0", version);
+    }
+
+    @Test
+    public void updateMainDefaultDependencies_polymerVersionIsProvided_useProvided() {
+        JsonObject object = Json.createObject();
+        nodeUpdater.updateMainDefaultDependencies(object, "foo");
+
+        String version = getPolymerVersion(object);
+        Assert.assertEquals("foo", version);
+    }
+
+    private String getPolymerVersion(JsonObject object) {
+        JsonObject deps = object.get("dependencies");
+        String version = deps.getString("@polymer/polymer");
+        return version;
+    }
+
     private void resolveResource_happyPath(String resourceFolder) {
         Mockito.when(finder.getResource(resourceFolder + "/foo"))
                 .thenReturn(url);
diff --git a/flow-server/src/test/java/com/vaadin/flow/server/frontend/scanner/ClassFinderTest.java b/flow-server/src/test/java/com/vaadin/flow/server/frontend/scanner/ClassFinderTest.java
index 02cd5b9d4ea..38c53afe3cd 100644
--- a/flow-server/src/test/java/com/vaadin/flow/server/frontend/scanner/ClassFinderTest.java
+++ b/flow-server/src/test/java/com/vaadin/flow/server/frontend/scanner/ClassFinderTest.java
@@ -1,8 +1,11 @@
 package com.vaadin.flow.server.frontend.scanner;
 
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
 
 import org.junit.Assert;
 import org.junit.Rule;
@@ -17,30 +20,58 @@ public class ClassFinderTest {
     @Rule
     public ExpectedException exception = ExpectedException.none();
 
+    private static class TestList extends ArrayList {
+
+    }
+
     @Test
     public void should_Fail_when_DifferentClasLoader() throws Exception {
         ClassLoader loader = new ClassLoader() {
             @Override
-            public Class loadClass(String name) throws ClassNotFoundException {
+            public Class loadClass(String name)
+                    throws ClassNotFoundException {
                 throw new ClassNotFoundException();
             }
         };
 
         exception.expect(ClassNotFoundException.class);
-        DefaultClassFinder finder = new DefaultClassFinder(loader, Component1.class);
+        DefaultClassFinder finder = new DefaultClassFinder(loader,
+                Component1.class);
         finder.loadClass(Component1.class.getName());
     }
 
     @Test
     public void should_LoadClasses() throws Exception {
-        DefaultClassFinder finder = new DefaultClassFinder(new HashSet<>(Arrays.asList(Component1.class)));
+        DefaultClassFinder finder = new DefaultClassFinder(
+                new HashSet<>(Arrays.asList(Component1.class)));
         Assert.assertNotNull(finder.loadClass(Component1.class.getName()));
     }
 
     @Test
     public void should_LoadClasses_when_NoClassListProvided() throws Exception {
-        DefaultClassFinder finder = new DefaultClassFinder(Collections.emptySet());
+        DefaultClassFinder finder = new DefaultClassFinder(
+                Collections.emptySet());
         Assert.assertNotNull(finder.loadClass(Component1.class.getName()));
     }
 
+    @Test
+    public void getSubTypesOf_returnsPlainSubtypes() {
+        DefaultClassFinder finder = new DefaultClassFinder(new HashSet<>(
+                Arrays.asList(Double.class, Integer.class, String.class)));
+        Set> subTypes = finder
+                .getSubTypesOf(Number.class);
+        Assert.assertEquals(2, subTypes.size());
+        Assert.assertTrue(subTypes.contains(Double.class));
+        Assert.assertTrue(subTypes.contains(Integer.class));
+    }
+
+    @Test
+    public void getSubTypesOf_returnsGenericSubtypes() {
+        DefaultClassFinder finder = new DefaultClassFinder(new HashSet<>(
+                Arrays.asList(ArrayList.class, TestList.class, String.class)));
+        Set> subTypes = finder.getSubTypesOf(List.class);
+        Assert.assertEquals(2, subTypes.size());
+        Assert.assertTrue(subTypes.contains(ArrayList.class));
+        Assert.assertTrue(subTypes.contains(TestList.class));
+    }
 }
diff --git a/flow-server/src/test/java/com/vaadin/flow/server/frontend/scanner/FrontendDependenciesTest.java b/flow-server/src/test/java/com/vaadin/flow/server/frontend/scanner/FrontendDependenciesTest.java
index 12402226f68..3bcfa7fe3ac 100644
--- a/flow-server/src/test/java/com/vaadin/flow/server/frontend/scanner/FrontendDependenciesTest.java
+++ b/flow-server/src/test/java/com/vaadin/flow/server/frontend/scanner/FrontendDependenciesTest.java
@@ -32,9 +32,11 @@
 import com.vaadin.flow.component.Component;
 import com.vaadin.flow.component.WebComponentExporter;
 import com.vaadin.flow.component.webcomponent.WebComponent;
+import com.vaadin.flow.router.HasErrorParameter;
 import com.vaadin.flow.router.Route;
 import com.vaadin.flow.server.UIInitListener;
 import com.vaadin.flow.server.VaadinServiceInitListener;
+import com.vaadin.flow.server.frontend.scanner.samples.ErrorComponent;
 import com.vaadin.flow.server.frontend.scanner.samples.JsOrderComponent;
 import com.vaadin.flow.server.frontend.scanner.samples.MyServiceListener;
 import com.vaadin.flow.server.frontend.scanner.samples.MyUIInitListener;
@@ -61,10 +63,13 @@ public void setUp() throws ClassNotFoundException {
                 .loadClass(VaadinServiceInitListener.class.getName()))
                 .thenReturn((Class) VaadinServiceInitListener.class);
 
-        Mockito.when(classFinder
-                .loadClass(WebComponentExporter.class.getName()))
+        Mockito.when(
+                classFinder.loadClass(WebComponentExporter.class.getName()))
                 .thenReturn((Class) WebComponentExporter.class);
 
+        Mockito.when(classFinder.loadClass(HasErrorParameter.class.getName()))
+                .thenReturn((Class) HasErrorParameter.class);
+
         Mockito.when(classFinder.loadClass(FrontendDependencies.LUMO))
                 .thenReturn((Class) FakeLumo.class);
 
@@ -90,6 +95,22 @@ public void routedComponent_endpointsAreCollected()
         Assert.assertEquals("bar.js", scripts.iterator().next());
     }
 
+    @Test
+    public void hasErrorParameterComponent_endpointIsCollected()
+            throws ClassNotFoundException {
+        Mockito.when(classFinder.getSubTypesOf(HasErrorParameter.class))
+                .thenReturn(Collections.singleton(ErrorComponent.class));
+        FrontendDependencies dependencies = new FrontendDependencies(
+                classFinder, false);
+        List modules = dependencies.getModules();
+        Assert.assertEquals(1, modules.size());
+        Assert.assertEquals("./src/bar.js", modules.get(0));
+
+        Set scripts = dependencies.getScripts();
+        Assert.assertEquals(1, scripts.size());
+        Assert.assertEquals("./src/baz.js", scripts.iterator().next());
+    }
+
     @Test
     public void componentInsideUiInitListener_endpointsAreCollected()
             throws ClassNotFoundException {
@@ -139,25 +160,24 @@ public void jsScriptOrderIsPreserved() throws ClassNotFoundException {
     // flow #6408
     @Test
     public void annotationsInRouterLayoutWontBeFlaggedAsBelongingToTheme() {
-        Mockito.when(classFinder.getAnnotatedClasses(Route.class))
-                .thenReturn(Collections.singleton(RouteComponentWithLayout.class));
+        Mockito.when(classFinder.getAnnotatedClasses(Route.class)).thenReturn(
+                Collections.singleton(RouteComponentWithLayout.class));
         FrontendDependencies dependencies = new FrontendDependencies(
                 classFinder, false);
 
         List expectedOrder = Arrays.asList("theme-foo.js", "foo.js");
         Assert.assertThat("Theme's annotations should come first",
-                    dependencies.getModules(), is(expectedOrder)
-                );
+                dependencies.getModules(), is(expectedOrder));
     }
 
     // flow #6524
     @Test
     public void extractsAndScansClassesFromMethodReferences() {
-        Mockito.when(classFinder.getAnnotatedClasses(Route.class))
-                .thenReturn(Collections.singleton(RouteComponentWithMethodReference.class));
+        Mockito.when(classFinder.getAnnotatedClasses(Route.class)).thenReturn(
+                Collections.singleton(RouteComponentWithMethodReference.class));
 
-        FrontendDependencies dependencies =
-                new FrontendDependencies(classFinder, false);
+        FrontendDependencies dependencies = new FrontendDependencies(
+                classFinder, false);
 
         List modules = dependencies.getModules();
         Assert.assertEquals(3, modules.size());
@@ -180,7 +200,8 @@ public void defaultThemeIsLoadedForExporters() throws Exception {
         Assert.assertNotNull(dependencies.getThemeDefinition());
     }
 
-    public static class MyComponent extends Component {}
+    public static class MyComponent extends Component {
+    }
 
     public static class MyExporter extends WebComponentExporter {
         public MyExporter() {
@@ -188,11 +209,14 @@ public MyExporter() {
         }
 
         @Override
-        protected void configureInstance(WebComponent webComponent, MyComponent component) { }
+        protected void configureInstance(WebComponent webComponent,
+                MyComponent component) {
+        }
     }
 
     public static class FakeLumo implements AbstractTheme {
-        public FakeLumo() {}
+        public FakeLumo() {
+        }
 
         @Override
         public String getBaseUrl() {
diff --git a/flow-server/src/test/java/com/vaadin/flow/server/frontend/scanner/samples/ErrorComponent.java b/flow-server/src/test/java/com/vaadin/flow/server/frontend/scanner/samples/ErrorComponent.java
new file mode 100644
index 00000000000..5d4a10615e3
--- /dev/null
+++ b/flow-server/src/test/java/com/vaadin/flow/server/frontend/scanner/samples/ErrorComponent.java
@@ -0,0 +1,34 @@
+/*
+ * Copyright 2000-2018 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.flow.server.frontend.scanner.samples;
+
+import com.vaadin.flow.component.dependency.JavaScript;
+import com.vaadin.flow.component.dependency.JsModule;
+import com.vaadin.flow.router.BeforeEnterEvent;
+import com.vaadin.flow.router.ErrorParameter;
+import com.vaadin.flow.router.HasErrorParameter;
+
+@JsModule("./src/bar.js")
+@JavaScript("./src/baz.js")
+public class ErrorComponent implements HasErrorParameter {
+
+    @Override
+    public int setErrorParameter(BeforeEnterEvent event,
+            ErrorParameter parameter) {
+        return 0;
+    }
+
+}
diff --git a/flow-server/src/test/java/com/vaadin/flow/server/startup/DevModeClassFinderTest.java b/flow-server/src/test/java/com/vaadin/flow/server/startup/DevModeClassFinderTest.java
index 175ec10dbbb..d52f8e54876 100644
--- a/flow-server/src/test/java/com/vaadin/flow/server/startup/DevModeClassFinderTest.java
+++ b/flow-server/src/test/java/com/vaadin/flow/server/startup/DevModeClassFinderTest.java
@@ -27,11 +27,12 @@
 import org.junit.Assert;
 import org.junit.Test;
 
-import com.vaadin.flow.component.internal.ExportsWebComponent;
 import com.vaadin.flow.component.dependency.CssImport;
 import com.vaadin.flow.component.dependency.JavaScript;
 import com.vaadin.flow.component.dependency.JsModule;
 import com.vaadin.flow.component.dependency.NpmPackage;
+import com.vaadin.flow.component.internal.ExportsWebComponent;
+import com.vaadin.flow.router.HasErrorParameter;
 import com.vaadin.flow.router.Route;
 import com.vaadin.flow.server.SessionInitListener;
 import com.vaadin.flow.server.UIInitListener;
@@ -66,12 +67,14 @@ public void applicableClasses_knownClasses() {
             CssImport.class,
             CssImport.Container.class,
             Theme.class,
-            NoTheme.class);
+            NoTheme.class,
+            HasErrorParameter.class);
 
         for (Class clz : classes) {
             assertTrue("should be a known class " + clz.getName(), knownClasses.contains(clz));
         }
         Assert.assertEquals(knownClasses.size(), classes.size());
+        Assert.assertEquals(15, classes.size());
     }
 
     @Test
diff --git a/flow-server/src/test/java/com/vaadin/flow/server/startup/DevModeInitializerTest.java b/flow-server/src/test/java/com/vaadin/flow/server/startup/DevModeInitializerTest.java
index 5034db49487..e935fa06a13 100644
--- a/flow-server/src/test/java/com/vaadin/flow/server/startup/DevModeInitializerTest.java
+++ b/flow-server/src/test/java/com/vaadin/flow/server/startup/DevModeInitializerTest.java
@@ -5,6 +5,8 @@
 import java.io.File;
 import java.io.IOException;
 import java.net.URL;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
 import java.nio.file.Paths;
 import java.util.ArrayList;
 import java.util.Collections;
@@ -12,6 +14,7 @@
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
+import java.util.stream.Collectors;
 
 import net.jcip.annotations.NotThreadSafe;
 import org.junit.Assert;
@@ -23,15 +26,18 @@
 
 import com.vaadin.flow.component.dependency.JsModule;
 import com.vaadin.flow.router.Route;
+import com.vaadin.flow.server.Constants;
 import com.vaadin.flow.server.DevModeHandler;
 import com.vaadin.flow.server.connect.generator.VaadinConnectClientGenerator;
 import com.vaadin.flow.server.frontend.FallbackChunk;
 
+import elemental.json.Json;
+import elemental.json.JsonObject;
+
 import static com.vaadin.flow.server.Constants.COMPATIBILITY_RESOURCES_FRONTEND_DEFAULT;
 import static com.vaadin.flow.server.Constants.CONNECT_JAVA_SOURCE_FOLDER_TOKEN;
 import static com.vaadin.flow.server.Constants.RESOURCES_FRONTEND_DEFAULT;
 import static com.vaadin.flow.server.Constants.SERVLET_PARAMETER_COMPATIBILITY_MODE;
-import static com.vaadin.flow.server.Constants.SERVLET_PARAMETER_DEVMODE_OPTIMIZE_BUNDLE;
 import static com.vaadin.flow.server.Constants.SERVLET_PARAMETER_PRODUCTION_MODE;
 import static com.vaadin.flow.server.Constants.SERVLET_PARAMETER_REUSE_DEV_SERVER;
 import static com.vaadin.flow.server.DevModeHandler.getDevModeHandler;
@@ -181,7 +187,7 @@ public void listener_should_stopDevModeHandler_onDestroy()
 
     @Test
     public void shouldUseByteCodeScannerIfPropertySet() throws Exception {
-        System.setProperty(SERVLET_PARAMETER_DEVMODE_OPTIMIZE_BUNDLE,
+        initParams.put(Constants.SERVLET_PARAMETER_DEVMODE_OPTIMIZE_BUNDLE,
                 "true");
         DevModeInitializer devModeInitializer = new DevModeInitializer();
         final Set> classes = new HashSet<>();
@@ -195,9 +201,25 @@ public void shouldUseByteCodeScannerIfPropertySet() throws Exception {
                 Mockito.eq(FallbackChunk.class.getName()), arg.capture());
         FallbackChunk fallbackChunk = arg.getValue();
         Assert.assertFalse(fallbackChunk.getModules().contains("foo"));
+
         Assert.assertTrue(fallbackChunk.getModules().contains("bar"));
     }
 
+    @Test
+    public void initDevModeHandler_usePolymerVersion() throws Exception {
+        DevModeInitializer devModeInitializer = new DevModeInitializer();
+        initParams.put(Constants.SERVLET_PARAMETER_DEVMODE_POLYMER_VERSION,
+                "3.3.0");
+        devModeInitializer.onStartup(Collections.emptySet(), servletContext);
+
+        String packageJson = Files
+                .readAllLines(mainPackageFile.toPath(), StandardCharsets.UTF_8)
+                .stream().collect(Collectors.joining());
+        JsonObject json = Json.parse(packageJson);
+        JsonObject deps = json.get("dependencies");
+        Assert.assertEquals("3.3.0", deps.getString("@polymer/polymer"));
+    }
+
     @Test
     public void shouldUseFullPathScannerByDefault() throws Exception {
         DevModeInitializer devModeInitializer = new DevModeInitializer();
diff --git a/flow-server/src/test/java/com/vaadin/flow/server/startup/DevModeInitializerTestBase.java b/flow-server/src/test/java/com/vaadin/flow/server/startup/DevModeInitializerTestBase.java
index c59fe0652c5..d8fc9f47ddb 100644
--- a/flow-server/src/test/java/com/vaadin/flow/server/startup/DevModeInitializerTestBase.java
+++ b/flow-server/src/test/java/com/vaadin/flow/server/startup/DevModeInitializerTestBase.java
@@ -58,7 +58,7 @@ public class DevModeInitializerTestBase {
     public final TemporaryFolder temporaryFolder = new TemporaryFolder();
 
     @Before
-    @SuppressWarnings({"unchecked", "rawtypes"})
+    @SuppressWarnings({ "unchecked", "rawtypes" })
     public void setup() throws Exception {
         assertNull(getDevModeHandler());
 
@@ -69,7 +69,8 @@ public void setup() throws Exception {
         createStubWebpackServer("Compiled", 500, baseDir);
 
         servletContext = Mockito.mock(ServletContext.class);
-        ServletRegistration registration = Mockito.mock(ServletRegistration.class);
+        ServletRegistration registration = Mockito
+                .mock(ServletRegistration.class);
 
         initParams = new HashMap<>();
         initParams.put(FrontendUtils.PROJECT_BASEDIR, baseDir);
@@ -111,7 +112,6 @@ public void teardown() throws Exception, SecurityException {
         System.clearProperty("vaadin." + SERVLET_PARAMETER_COMPATIBILITY_MODE);
         System.clearProperty("vaadin." + SERVLET_PARAMETER_PRODUCTION_MODE);
         System.clearProperty("vaadin." + SERVLET_PARAMETER_REUSE_DEV_SERVER);
-        System.clearProperty("vaadin." + SERVLET_PARAMETER_DEVMODE_OPTIMIZE_BUNDLE);
         System.clearProperty("vaadin." + CONNECT_JAVA_SOURCE_FOLDER_TOKEN);
 
         webpackFile.delete();
@@ -131,7 +131,6 @@ public void runDestroy() throws Exception {
         devModeInitializer.contextDestroyed(null);
     }
 
-
     static List getClasspathURLs() {
         return Arrays.stream(
                 System.getProperty("java.class.path").split(File.pathSeparator))
diff --git a/flow-server/src/test/java/com/vaadin/tests/util/MockUI.java b/flow-server/src/test/java/com/vaadin/tests/util/MockUI.java
index 2ef02e3fbd5..55868a2ed15 100644
--- a/flow-server/src/test/java/com/vaadin/tests/util/MockUI.java
+++ b/flow-server/src/test/java/com/vaadin/tests/util/MockUI.java
@@ -15,9 +15,12 @@
  */
 package com.vaadin.tests.util;
 
+import java.util.List;
+
 import org.mockito.Mockito;
 
 import com.vaadin.flow.component.UI;
+import com.vaadin.flow.component.internal.PendingJavaScriptInvocation;
 import com.vaadin.flow.function.DeploymentConfiguration;
 import com.vaadin.flow.server.VaadinRequest;
 import com.vaadin.flow.server.VaadinService;
@@ -39,6 +42,13 @@ protected void init(VaadinRequest request) {
         // Do nothing
     }
 
+    public List dumpPendingJsInvocations() {
+        // Ensure element invocations are also flushed
+        getInternals().getStateTree().runExecutionsBeforeClientResponse();
+
+        return getInternals().dumpPendingJavaScriptInvocations();
+    }
+
     private static VaadinSession findOrCreateSession() {
         VaadinSession session = VaadinSession.getCurrent();
         if (session == null) {
diff --git a/flow-server/src/test/resources/META-INF/VAADIN/config/babel_stats.json b/flow-server/src/test/resources/META-INF/VAADIN/config/babel_stats.json
index d4aa333f93c..e7d27c0ce27 100644
--- a/flow-server/src/test/resources/META-INF/VAADIN/config/babel_stats.json
+++ b/flow-server/src/test/resources/META-INF/VAADIN/config/babel_stats.json
@@ -1,19976 +1,13 @@
 {
- "errors": [],
- "warnings": [],
- "version": "4.29.6",
  "hash": "e251827e9f087691baf2",
- "publicPath": "",
- "outputPath": "C:\\Users\\mikae\\Code\\flow\\flow-tests\\test-npm/src/main/webapp",
- "assetsByChunkName": {
-  "index": "build/index.js",
-  "index.es5": "build/index.es5.js"
- },
- "assets": [
-  {
-   "name": "build/index.es5.js",
-   "size": 198541,
-   "chunks": [
-    1
-   ],
-   "chunkNames": [
-    "index.es5"
-   ],
-   "emitted": true
-  },
-  {
-   "name": "build/index.js",
-   "size": 191156,
-   "chunks": [
-    0
-   ],
-   "chunkNames": [
-    "index"
-   ],
-   "emitted": true
-  },
-  {
-   "name": "build/webcomponentsjs/LICENSE.md",
-   "size": 1559,
-   "chunks": [],
-   "chunkNames": [],
-   "emitted": true
-  },
-  {
-   "name": "build/webcomponentsjs/README.md",
-   "size": 10783,
-   "chunks": [],
-   "chunkNames": [],
-   "emitted": true
-  },
-  {
-   "name": "build/webcomponentsjs/bundles/webcomponents-ce.js",
-   "size": 16910,
-   "chunks": [],
-   "chunkNames": [],
-   "emitted": true
-  },
-  {
-   "name": "build/webcomponentsjs/bundles/webcomponents-ce.js.map",
-   "size": 104300,
-   "chunks": [],
-   "chunkNames": [],
-   "emitted": true
-  },
-  {
-   "name": "build/webcomponentsjs/bundles/webcomponents-sd-ce-pf.js",
-   "size": 109183,
-   "chunks": [],
-   "chunkNames": [],
-   "emitted": true
-  },
-  {
-   "name": "build/webcomponentsjs/bundles/webcomponents-sd-ce-pf.js.map",
-   "size": 649507,
-   "chunks": [],
-   "chunkNames": [],
-   "emitted": true
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-  {
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-   "chunks": [],
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-   "emitted": true
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-  {
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-   "size": 942,
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-   "emitted": true
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-   "size": 6272,
-   "chunks": [],
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-   "emitted": true
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- "entrypoints": {
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-       "module": "(webpack)/hot sync nonrecursive ^\\.\\/log$",
-       "moduleName": "(webpack)/hot sync nonrecursive ^\\.\\/log$",
-       "type": "context element",
-       "userRequest": "./log",
-       "loc": "./log"
-      }
-     ],
-     "usedExports": true,
-     "providedExports": null,
-     "optimizationBailout": [
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['DownRightVectorBar', [10583]], ['DownRightVector', [8641]], ['DownTeeArrow', [8615]], ['DownTee', [8868]], ['drbkarow', [10512]], ['drcorn', [8991]], ['drcrop', [8972]], ['Dscr', [119967]], ['dscr', [119993]], ['DScy', [1029]], ['dscy', [1109]], ['dsol', [10742]], ['Dstrok', [272]], ['dstrok', [273]], ['dtdot', [8945]], ['dtri', [9663]], ['dtrif', [9662]], ['duarr', [8693]], ['duhar', [10607]], ['dwangle', [10662]], ['DZcy', [1039]], ['dzcy', [1119]], ['dzigrarr', [10239]], ['Eacute', [201]], ['eacute', [233]], ['easter', [10862]], ['Ecaron', [282]], ['ecaron', [283]], ['Ecirc', [202]], ['ecirc', [234]], ['ecir', [8790]], ['ecolon', [8789]], ['Ecy', [1069]], ['ecy', [1101]], ['eDDot', [10871]], ['Edot', [278]], ['edot', [279]], ['eDot', [8785]], ['ee', [8519]], ['efDot', [8786]], ['Efr', [120072]], ['efr', [120098]], ['eg', [10906]], ['Egrave', [200]], ['egrave', [232]], ['egs', [10902]], ['egsdot', [10904]], ['el', [10905]], ['Element', [8712]], ['elinters', [9191]], ['ell', 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['frac78', [8542]], ['frasl', [8260]], ['frown', [8994]], ['fscr', [119995]], ['Fscr', [8497]], ['gacute', [501]], ['Gamma', [915]], ['gamma', [947]], ['Gammad', [988]], ['gammad', [989]], ['gap', [10886]], ['Gbreve', [286]], ['gbreve', [287]], ['Gcedil', [290]], ['Gcirc', [284]], ['gcirc', [285]], ['Gcy', [1043]], ['gcy', [1075]], ['Gdot', [288]], ['gdot', [289]], ['ge', [8805]], ['gE', [8807]], ['gEl', [10892]], ['gel', [8923]], ['geq', [8805]], ['geqq', [8807]], ['geqslant', [10878]], ['gescc', [10921]], ['ges', [10878]], ['gesdot', [10880]], ['gesdoto', [10882]], ['gesdotol', [10884]], ['gesl', [8923, 65024]], ['gesles', [10900]], ['Gfr', [120074]], ['gfr', [120100]], ['gg', [8811]], ['Gg', [8921]], ['ggg', [8921]], ['gimel', [8503]], ['GJcy', [1027]], ['gjcy', [1107]], ['gla', [10917]], ['gl', [8823]], ['glE', [10898]], ['glj', [10916]], ['gnap', [10890]], ['gnapprox', [10890]], ['gne', [10888]], ['gnE', [8809]], ['gneq', [10888]], ['gneqq', [8809]], ['gnsim', [8935]], ['Gopf', 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['hellip', [8230]], ['hercon', [8889]], ['hfr', [120101]], ['Hfr', [8460]], ['HilbertSpace', [8459]], ['hksearow', [10533]], ['hkswarow', [10534]], ['hoarr', [8703]], ['homtht', [8763]], ['hookleftarrow', [8617]], ['hookrightarrow', [8618]], ['hopf', [120153]], ['Hopf', [8461]], ['horbar', [8213]], ['HorizontalLine', [9472]], ['hscr', [119997]], ['Hscr', [8459]], ['hslash', [8463]], ['Hstrok', [294]], ['hstrok', [295]], ['HumpDownHump', [8782]], ['HumpEqual', [8783]], ['hybull', [8259]], ['hyphen', [8208]], ['Iacute', [205]], ['iacute', [237]], ['ic', [8291]], ['Icirc', [206]], ['icirc', [238]], ['Icy', [1048]], ['icy', [1080]], ['Idot', [304]], ['IEcy', [1045]], ['iecy', [1077]], ['iexcl', [161]], ['iff', [8660]], ['ifr', [120102]], ['Ifr', [8465]], ['Igrave', [204]], ['igrave', [236]], ['ii', [8520]], ['iiiint', [10764]], ['iiint', [8749]], ['iinfin', [10716]], ['iiota', [8489]], ['IJlig', [306]], ['ijlig', [307]], ['Imacr', [298]], ['imacr', [299]], ['image', [8465]], ['ImaginaryI', [8520]], ['imagline', [8464]], ['imagpart', [8465]], ['imath', [305]], ['Im', [8465]], ['imof', [8887]], ['imped', [437]], ['Implies', [8658]], ['incare', [8453]], ['in', [8712]], ['infin', [8734]], ['infintie', [10717]], ['inodot', [305]], ['intcal', [8890]], ['int', [8747]], ['Int', [8748]], ['integers', [8484]], ['Integral', [8747]], ['intercal', [8890]], ['Intersection', [8898]], ['intlarhk', [10775]], ['intprod', [10812]], ['InvisibleComma', [8291]], ['InvisibleTimes', [8290]], ['IOcy', [1025]], ['iocy', [1105]], ['Iogon', [302]], ['iogon', [303]], ['Iopf', [120128]], ['iopf', [120154]], ['Iota', [921]], ['iota', [953]], ['iprod', [10812]], ['iquest', [191]], ['iscr', [119998]], ['Iscr', [8464]], ['isin', [8712]], ['isindot', [8949]], ['isinE', [8953]], ['isins', [8948]], ['isinsv', [8947]], ['isinv', [8712]], ['it', [8290]], ['Itilde', [296]], ['itilde', [297]], ['Iukcy', [1030]], ['iukcy', [1110]], ['Iuml', [207]], ['iuml', [239]], ['Jcirc', [308]], ['jcirc', [309]], ['Jcy', [1049]], ['jcy', [1081]], ['Jfr', [120077]], ['jfr', [120103]], ['jmath', [567]], ['Jopf', [120129]], ['jopf', [120155]], ['Jscr', [119973]], ['jscr', [119999]], ['Jsercy', [1032]], ['jsercy', [1112]], ['Jukcy', [1028]], ['jukcy', [1108]], ['Kappa', [922]], ['kappa', [954]], ['kappav', [1008]], ['Kcedil', [310]], ['kcedil', [311]], ['Kcy', [1050]], ['kcy', [1082]], ['Kfr', [120078]], ['kfr', [120104]], ['kgreen', [312]], ['KHcy', [1061]], ['khcy', [1093]], ['KJcy', [1036]], ['kjcy', [1116]], ['Kopf', [120130]], ['kopf', [120156]], ['Kscr', [119974]], ['kscr', [120000]], ['lAarr', [8666]], ['Lacute', [313]], ['lacute', [314]], ['laemptyv', [10676]], ['lagran', [8466]], ['Lambda', [923]], ['lambda', [955]], ['lang', [10216]], ['Lang', [10218]], ['langd', [10641]], ['langle', [10216]], ['lap', [10885]], ['Laplacetrf', [8466]], ['laquo', [171]], ['larrb', [8676]], ['larrbfs', [10527]], ['larr', [8592]], ['Larr', [8606]], ['lArr', [8656]], ['larrfs', [10525]], ['larrhk', [8617]], ['larrlp', [8619]], ['larrpl', [10553]], ['larrsim', [10611]], ['larrtl', [8610]], ['latail', [10521]], ['lAtail', [10523]], ['lat', [10923]], ['late', [10925]], ['lates', [10925, 65024]], ['lbarr', [10508]], ['lBarr', [10510]], ['lbbrk', [10098]], ['lbrace', [123]], ['lbrack', [91]], ['lbrke', [10635]], ['lbrksld', [10639]], ['lbrkslu', [10637]], ['Lcaron', [317]], ['lcaron', [318]], ['Lcedil', [315]], ['lcedil', [316]], ['lceil', [8968]], ['lcub', [123]], ['Lcy', [1051]], ['lcy', [1083]], ['ldca', [10550]], ['ldquo', [8220]], ['ldquor', [8222]], ['ldrdhar', [10599]], ['ldrushar', [10571]], ['ldsh', [8626]], ['le', [8804]], ['lE', [8806]], ['LeftAngleBracket', [10216]], ['LeftArrowBar', [8676]], ['leftarrow', [8592]], ['LeftArrow', [8592]], ['Leftarrow', [8656]], ['LeftArrowRightArrow', [8646]], ['leftarrowtail', [8610]], ['LeftCeiling', [8968]], ['LeftDoubleBracket', [10214]], ['LeftDownTeeVector', [10593]], ['LeftDownVectorBar', [10585]], ['LeftDownVector', [8643]], ['LeftFloor', [8970]], ['leftharpoondown', [8637]], ['leftharpoonup', [8636]], ['leftleftarrows', [8647]], ['leftrightarrow', [8596]], ['LeftRightArrow', [8596]], ['Leftrightarrow', [8660]], ['leftrightarrows', [8646]], ['leftrightharpoons', [8651]], ['leftrightsquigarrow', [8621]], ['LeftRightVector', [10574]], ['LeftTeeArrow', [8612]], ['LeftTee', [8867]], ['LeftTeeVector', [10586]], ['leftthreetimes', [8907]], ['LeftTriangleBar', [10703]], ['LeftTriangle', [8882]], ['LeftTriangleEqual', [8884]], ['LeftUpDownVector', [10577]], ['LeftUpTeeVector', [10592]], ['LeftUpVectorBar', [10584]], ['LeftUpVector', [8639]], ['LeftVectorBar', [10578]], ['LeftVector', [8636]], ['lEg', [10891]], ['leg', [8922]], ['leq', [8804]], ['leqq', [8806]], ['leqslant', [10877]], ['lescc', [10920]], ['les', [10877]], ['lesdot', [10879]], ['lesdoto', [10881]], ['lesdotor', [10883]], ['lesg', [8922, 65024]], ['lesges', [10899]], ['lessapprox', [10885]], ['lessdot', [8918]], ['lesseqgtr', [8922]], ['lesseqqgtr', [10891]], ['LessEqualGreater', [8922]], ['LessFullEqual', [8806]], ['LessGreater', [8822]], ['lessgtr', [8822]], ['LessLess', [10913]], ['lesssim', [8818]], ['LessSlantEqual', [10877]], ['LessTilde', [8818]], ['lfisht', [10620]], ['lfloor', [8970]], ['Lfr', [120079]], ['lfr', [120105]], ['lg', [8822]], ['lgE', [10897]], ['lHar', [10594]], ['lhard', [8637]], ['lharu', [8636]], ['lharul', [10602]], ['lhblk', [9604]], ['LJcy', [1033]], ['ljcy', [1113]], ['llarr', [8647]], ['ll', [8810]], ['Ll', [8920]], ['llcorner', [8990]], ['Lleftarrow', [8666]], ['llhard', [10603]], ['lltri', [9722]], ['Lmidot', [319]], ['lmidot', [320]], ['lmoustache', [9136]], ['lmoust', [9136]], ['lnap', [10889]], ['lnapprox', [10889]], ['lne', [10887]], ['lnE', [8808]], ['lneq', [10887]], ['lneqq', [8808]], ['lnsim', [8934]], ['loang', [10220]], ['loarr', [8701]], ['lobrk', [10214]], ['longleftarrow', [10229]], ['LongLeftArrow', [10229]], ['Longleftarrow', [10232]], ['longleftrightarrow', [10231]], ['LongLeftRightArrow', [10231]], ['Longleftrightarrow', [10234]], ['longmapsto', [10236]], ['longrightarrow', [10230]], ['LongRightArrow', [10230]], ['Longrightarrow', [10233]], ['looparrowleft', [8619]], ['looparrowright', [8620]], ['lopar', [10629]], ['Lopf', [120131]], ['lopf', [120157]], ['loplus', [10797]], ['lotimes', [10804]], ['lowast', [8727]], ['lowbar', [95]], ['LowerLeftArrow', [8601]], ['LowerRightArrow', [8600]], ['loz', [9674]], ['lozenge', [9674]], ['lozf', [10731]], ['lpar', [40]], ['lparlt', [10643]], ['lrarr', [8646]], ['lrcorner', [8991]], ['lrhar', [8651]], ['lrhard', [10605]], ['lrm', [8206]], ['lrtri', [8895]], ['lsaquo', [8249]], ['lscr', [120001]], ['Lscr', [8466]], ['lsh', [8624]], ['Lsh', [8624]], ['lsim', [8818]], ['lsime', [10893]], ['lsimg', [10895]], ['lsqb', [91]], ['lsquo', [8216]], ['lsquor', [8218]], ['Lstrok', [321]], ['lstrok', [322]], ['ltcc', [10918]], ['ltcir', [10873]], ['lt', [60]], ['LT', [60]], ['Lt', [8810]], ['ltdot', [8918]], ['lthree', [8907]], ['ltimes', [8905]], ['ltlarr', [10614]], ['ltquest', [10875]], ['ltri', [9667]], ['ltrie', [8884]], ['ltrif', [9666]], ['ltrPar', [10646]], ['lurdshar', [10570]], ['luruhar', [10598]], ['lvertneqq', [8808, 65024]], ['lvnE', [8808, 65024]], ['macr', [175]], ['male', [9794]], ['malt', [10016]], ['maltese', [10016]], ['Map', [10501]], ['map', [8614]], ['mapsto', [8614]], ['mapstodown', [8615]], ['mapstoleft', [8612]], ['mapstoup', [8613]], ['marker', [9646]], ['mcomma', [10793]], ['Mcy', [1052]], ['mcy', [1084]], ['mdash', [8212]], ['mDDot', [8762]], ['measuredangle', [8737]], ['MediumSpace', [8287]], ['Mellintrf', [8499]], ['Mfr', [120080]], ['mfr', [120106]], ['mho', [8487]], ['micro', [181]], ['midast', [42]], ['midcir', [10992]], ['mid', [8739]], ['middot', [183]], ['minusb', [8863]], ['minus', [8722]], ['minusd', [8760]], ['minusdu', [10794]], ['MinusPlus', [8723]], ['mlcp', [10971]], ['mldr', [8230]], ['mnplus', [8723]], ['models', [8871]], ['Mopf', [120132]], ['mopf', [120158]], ['mp', 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['vsubne', [8842, 65024]], ['vsupnE', [10956, 65024]], ['vsupne', [8843, 65024]], ['Vvdash', [8874]], ['vzigzag', [10650]], ['Wcirc', [372]], ['wcirc', [373]], ['wedbar', [10847]], ['wedge', [8743]], ['Wedge', [8896]], ['wedgeq', [8793]], ['weierp', [8472]], ['Wfr', [120090]], ['wfr', [120116]], ['Wopf', [120142]], ['wopf', [120168]], ['wp', [8472]], ['wr', [8768]], ['wreath', [8768]], ['Wscr', [119986]], ['wscr', [120012]], ['xcap', [8898]], ['xcirc', [9711]], ['xcup', [8899]], ['xdtri', [9661]], ['Xfr', [120091]], ['xfr', [120117]], ['xharr', [10231]], ['xhArr', [10234]], ['Xi', [926]], ['xi', [958]], ['xlarr', [10229]], ['xlArr', [10232]], ['xmap', [10236]], ['xnis', [8955]], ['xodot', [10752]], ['Xopf', [120143]], ['xopf', [120169]], ['xoplus', [10753]], ['xotime', [10754]], ['xrarr', [10230]], ['xrArr', [10233]], ['Xscr', [119987]], ['xscr', [120013]], ['xsqcup', [10758]], ['xuplus', [10756]], ['xutri', [9651]], ['xvee', [8897]], ['xwedge', [8896]], ['Yacute', [221]], ['yacute', [253]], ['YAcy', [1071]], ['yacy', [1103]], ['Ycirc', [374]], ['ycirc', [375]], ['Ycy', [1067]], ['ycy', [1099]], ['yen', [165]], ['Yfr', [120092]], ['yfr', [120118]], ['YIcy', [1031]], ['yicy', [1111]], ['Yopf', [120144]], ['yopf', [120170]], ['Yscr', [119988]], ['yscr', [120014]], ['YUcy', [1070]], ['yucy', [1102]], ['yuml', [255]], ['Yuml', [376]], ['Zacute', [377]], ['zacute', [378]], ['Zcaron', [381]], ['zcaron', [382]], ['Zcy', [1047]], ['zcy', [1079]], ['Zdot', [379]], ['zdot', [380]], ['zeetrf', [8488]], ['ZeroWidthSpace', [8203]], ['Zeta', [918]], ['zeta', [950]], ['zfr', [120119]], ['Zfr', [8488]], ['ZHcy', [1046]], ['zhcy', [1078]], ['zigrarr', [8669]], ['zopf', [120171]], ['Zopf', [8484]], ['Zscr', [119989]], ['zscr', [120015]], ['zwj', [8205]], ['zwnj', [8204]]];\n\nvar alphaIndex = {};\nvar charIndex = {};\n\ncreateIndexes(alphaIndex, charIndex);\n\n/**\n * @constructor\n */\nfunction Html5Entities() {}\n\n/**\n * @param {String} str\n * @returns {String}\n */\nHtml5Entities.prototype.decode = function(str) {\n    if (!str || !str.length) {\n        return '';\n    }\n    return str.replace(/&(#?[\\w\\d]+);?/g, function(s, entity) {\n        var chr;\n        if (entity.charAt(0) === \"#\") {\n            var code = entity.charAt(1) === 'x' ?\n                parseInt(entity.substr(2).toLowerCase(), 16) :\n                parseInt(entity.substr(1));\n\n            if (!(isNaN(code) || code < -32768 || code > 65535)) {\n                chr = String.fromCharCode(code);\n            }\n        } else {\n            chr = alphaIndex[entity];\n        }\n        return chr || s;\n    });\n};\n\n/**\n * @param {String} str\n * @returns {String}\n */\n Html5Entities.decode = function(str) {\n    return new Html5Entities().decode(str);\n };\n\n/**\n * @param {String} str\n * @returns {String}\n */\nHtml5Entities.prototype.encode = function(str) {\n    if (!str || !str.length) {\n        return '';\n    }\n    var strLength = str.length;\n    var result = '';\n    var i = 0;\n    while (i < strLength) {\n        var charInfo = charIndex[str.charCodeAt(i)];\n        if (charInfo) {\n            var alpha = charInfo[str.charCodeAt(i + 1)];\n            if (alpha) {\n                i++;\n            } else {\n                alpha = charInfo[''];\n            }\n            if (alpha) {\n                result += \"&\" + alpha + \";\";\n                i++;\n                continue;\n            }\n        }\n        result += str.charAt(i);\n        i++;\n    }\n    return result;\n};\n\n/**\n * @param {String} str\n * @returns {String}\n */\n Html5Entities.encode = function(str) {\n    return new Html5Entities().encode(str);\n };\n\n/**\n * @param {String} str\n * @returns {String}\n */\nHtml5Entities.prototype.encodeNonUTF = function(str) {\n    if (!str || !str.length) {\n        return '';\n    }\n    var strLength = str.length;\n    var result = '';\n    var i = 0;\n    while (i < strLength) {\n        var c = str.charCodeAt(i);\n        var charInfo = charIndex[c];\n        if (charInfo) {\n            var alpha = charInfo[str.charCodeAt(i + 1)];\n            if (alpha) {\n                i++;\n            } else {\n                alpha = charInfo[''];\n            }\n            if (alpha) {\n                result += \"&\" + alpha + \";\";\n                i++;\n                continue;\n            }\n        }\n        if (c < 32 || c > 126) {\n            result += '&#' + c + ';';\n        } else {\n            result += str.charAt(i);\n        }\n        i++;\n    }\n    return result;\n};\n\n/**\n * @param {String} str\n * @returns {String}\n */\n Html5Entities.encodeNonUTF = function(str) {\n    return new Html5Entities().encodeNonUTF(str);\n };\n\n/**\n * @param {String} str\n * @returns {String}\n */\nHtml5Entities.prototype.encodeNonASCII = function(str) {\n    if (!str || !str.length) {\n        return '';\n    }\n    var strLength = str.length;\n    var result = '';\n    var i = 0;\n    while (i < strLength) {\n        var c = str.charCodeAt(i);\n        if (c <= 255) {\n            result += str[i++];\n            continue;\n        }\n        result += '&#' + c + ';';\n        i++\n    }\n    return result;\n};\n\n/**\n * @param {String} str\n * @returns {String}\n */\n Html5Entities.encodeNonASCII = function(str) {\n    return new Html5Entities().encodeNonASCII(str);\n };\n\n/**\n * @param {Object} alphaIndex Passed by reference.\n * @param {Object} charIndex Passed by reference.\n */\nfunction createIndexes(alphaIndex, charIndex) {\n    var i = ENTITIES.length;\n    var _results = [];\n    while (i--) {\n        var e = ENTITIES[i];\n        var alpha = e[0];\n        var chars = e[1];\n        var chr = chars[0];\n        var addChar = (chr < 32 || chr > 126) || chr === 62 || chr === 60 || chr === 38 || chr === 34 || chr === 39;\n        var charInfo;\n        if (addChar) {\n            charInfo = charIndex[chr] = charIndex[chr] || {};\n        }\n        if (chars[1]) {\n            var chr2 = chars[1];\n            alphaIndex[alpha] = String.fromCharCode(chr) + String.fromCharCode(chr2);\n            _results.push(addChar && (charInfo[chr2] = alpha));\n        } else {\n            alphaIndex[alpha] = String.fromCharCode(chr);\n            _results.push(addChar && (charInfo[''] = alpha));\n        }\n    }\n}\n\nmodule.exports = Html5Entities;\n"
-    },
-    {
-     "id": 19,
-     "identifier": "multi C:\\Users\\mikae\\Code\\flow\\flow-tests\\test-npm\\node_modules\\webpack-dev-server\\client\\index.js?http://localhost:61902 ./main.js?babel-target=es6",
-     "name": "multi (webpack)-dev-server/client?http://localhost:61902#babel-target=es6 ./main.js?babel-target=es6",
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-     "errors": 0,
-     "warnings": 0,
-     "assets": [],
-     "reasons": [
-      {
-       "moduleId": null,
-       "moduleIdentifier": null,
-       "module": null,
-       "moduleName": null,
-       "type": "babel target multi entry"
-      }
-     ],
-     "usedExports": true,
-     "providedExports": null,
-     "optimizationBailout": [
-      "ModuleConcatenation bailout: Module is not an ECMAScript module"
-     ],
-     "depth": 0
-    },
-    {
-     "id": 20,
-     "identifier": "C:\\Users\\mikae\\Code\\flow\\flow-tests\\test-npm\\node_modules\\babel-loader\\lib\\index.js??ref--4-0!C:\\Users\\mikae\\Code\\flow\\flow-tests\\test-npm\\node_modules\\webpack-dev-server\\client\\index.js?http://localhost:61902&babel-target=es6",
-     "name": "(webpack)-dev-server/client?http://localhost:61902",
-     "index": 1,
-     "index2": 23,
-     "size": 8291,
-     "cacheable": true,
-     "built": true,
-     "optional": false,
-     "prefetched": false,
-     "chunks": [
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-     "issuer": "multi C:\\Users\\mikae\\Code\\flow\\flow-tests\\test-npm\\node_modules\\webpack-dev-server\\client\\index.js?http://localhost:61902 ./main.js?babel-target=es6",
-     "issuerId": 19,
-     "issuerName": "multi (webpack)-dev-server/client?http://localhost:61902#babel-target=es6 ./main.js?babel-target=es6",
-     "issuerPath": [
-      {
-       "id": 19,
-       "identifier": "multi C:\\Users\\mikae\\Code\\flow\\flow-tests\\test-npm\\node_modules\\webpack-dev-server\\client\\index.js?http://localhost:61902 ./main.js?babel-target=es6",
-       "name": "multi (webpack)-dev-server/client?http://localhost:61902#babel-target=es6 ./main.js?babel-target=es6"
-      }
-     ],
-     "failed": false,
-     "errors": 0,
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-     "assets": [],
-     "reasons": [
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-       "module": "multi (webpack)-dev-server/client?http://localhost:61902#babel-target=es6 ./main.js?babel-target=es6",
-       "moduleName": "multi (webpack)-dev-server/client?http://localhost:61902#babel-target=es6 ./main.js?babel-target=es6",
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-     "optimizationBailout": [
-      "ModuleConcatenation bailout: Module is not an ECMAScript module"
-     ],
-     "depth": 1,
-     "source": "'use strict';\n/* global __resourceQuery WorkerGlobalScope self */\n\n/* eslint prefer-destructuring: off */\n\nvar querystring = require('querystring');\n\nvar url = require('url');\n\nvar stripAnsi = require('strip-ansi');\n\nvar log = require('loglevel').getLogger('webpack-dev-server');\n\nvar socket = require('./socket');\n\nvar overlay = require('./overlay');\n\nfunction getCurrentScriptSource() {\n  // `document.currentScript` is the most accurate way to find the current script,\n  // but is not supported in all browsers.\n  if (document.currentScript) {\n    return document.currentScript.getAttribute('src');\n  } // Fall back to getting all scripts in the document.\n\n\n  var scriptElements = document.scripts || [];\n  var currentScript = scriptElements[scriptElements.length - 1];\n\n  if (currentScript) {\n    return currentScript.getAttribute('src');\n  } // Fail as there was no script to use.\n\n\n  throw new Error('[WDS] Failed to get current script source.');\n}\n\nvar urlParts;\nvar hotReload = true;\n\nif (typeof window !== 'undefined') {\n  var qs = window.location.search.toLowerCase();\n  hotReload = qs.indexOf('hotreload=false') === -1;\n}\n\nif (typeof __resourceQuery === 'string' && __resourceQuery) {\n  // If this bundle is inlined, use the resource query to get the correct url.\n  urlParts = url.parse(__resourceQuery.substr(1));\n} else {\n  // Else, get the url from the 
diff --git a/flow-tests/test-root-context/src/test/java/com/vaadin/flow/uitest/ui/PageIT.java b/flow-tests/test-root-context/src/test/java/com/vaadin/flow/uitest/ui/PageIT.java
index 477255b3cbd..5d682634217 100644
--- a/flow-tests/test-root-context/src/test/java/com/vaadin/flow/uitest/ui/PageIT.java
+++ b/flow-tests/test-root-context/src/test/java/com/vaadin/flow/uitest/ui/PageIT.java
@@ -6,6 +6,7 @@
 import org.junit.Assert;
 import org.junit.Test;
 import org.openqa.selenium.By;
+import org.openqa.selenium.JavascriptExecutor;
 import org.openqa.selenium.Keys;
 
 import com.vaadin.flow.component.html.testbench.InputTextElement;
@@ -84,10 +85,27 @@ public void testOpenUrlInNewTab() {
         open();
 
         findElement(By.id("open")).click();
-        ArrayList tabs = new ArrayList<>(getDriver().getWindowHandles());
+        ArrayList tabs = new ArrayList<>(
+                getDriver().getWindowHandles());
         Assert.assertThat(
                 getDriver().switchTo().window(tabs.get(1)).getCurrentUrl(),
-                Matchers.endsWith(BaseHrefView.class.getName())
-        );
+                Matchers.endsWith(BaseHrefView.class.getName()));
+    }
+
+    @Test
+    public void testOpenUrlInIFrame() throws InterruptedException {
+        open();
+
+        findElement(By.id("openInIFrame")).click();
+
+        waitUntil(driver -> !getIframeUrl().equals("about:blank"));
+
+        Assert.assertThat(getIframeUrl(),
+                Matchers.endsWith(BaseHrefView.class.getName()));
+    }
+
+    private String getIframeUrl() {
+        return (String) ((JavascriptExecutor) driver).executeScript(
+                "return document.getElementById('newWindow').contentWindow.location.href;");
     }
 }
diff --git a/flow-tests/test-root-context/src/test/java/com/vaadin/flow/uitest/ui/RouterSessionExpirationIT.java b/flow-tests/test-root-context/src/test/java/com/vaadin/flow/uitest/ui/RouterSessionExpirationIT.java
index 3e20c884f4d..3781ec59d60 100644
--- a/flow-tests/test-root-context/src/test/java/com/vaadin/flow/uitest/ui/RouterSessionExpirationIT.java
+++ b/flow-tests/test-root-context/src/test/java/com/vaadin/flow/uitest/ui/RouterSessionExpirationIT.java
@@ -17,9 +17,9 @@
 
 import org.junit.Assert;
 import org.junit.Test;
+import org.openqa.selenium.By;
 
 import com.vaadin.flow.testutil.ChromeBrowserTest;
-import org.openqa.selenium.By;
 
 public class RouterSessionExpirationIT extends ChromeBrowserTest {
 
@@ -37,9 +37,13 @@ public void navigationAfterSessionExpired() {
         navigateToFirstView();
         Assert.assertEquals(sessionId, getSessionId());
         navigateToSesssionExpireView();
-        Assert.assertEquals("No session", getSessionId());
-        navigateToFirstView();
+        // expired session causes page reload, after the page reload there will
+        // be a new session
         Assert.assertNotEquals(sessionId, getSessionId());
+        sessionId = getSessionId();
+        navigateToFirstView();
+        // session is preserved
+        Assert.assertEquals(sessionId, getSessionId());
     }
 
     @Test
diff --git a/flow-tests/test-root-context/src/test/java/com/vaadin/flow/uitest/ui/SessionCloseLogoutIT.java b/flow-tests/test-root-context/src/test/java/com/vaadin/flow/uitest/ui/SessionCloseLogoutIT.java
new file mode 100644
index 00000000000..24a3923c236
--- /dev/null
+++ b/flow-tests/test-root-context/src/test/java/com/vaadin/flow/uitest/ui/SessionCloseLogoutIT.java
@@ -0,0 +1,50 @@
+/*
+ * Copyright 2000-2019 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ *
+ */
+
+package com.vaadin.flow.uitest.ui;
+
+import org.junit.Assert;
+import org.junit.Test;
+import org.openqa.selenium.By;
+
+import com.vaadin.flow.component.html.testbench.NativeButtonElement;
+import com.vaadin.flow.testutil.ChromeBrowserTest;
+
+public class SessionCloseLogoutIT extends ChromeBrowserTest {
+
+    @Test
+    public void changeOnClient() throws InterruptedException {
+        open();
+
+        $(NativeButtonElement.class).first().click();
+
+        asserNoErrors();
+
+        waitUntil(driver -> !findElements(By.tagName("a")).isEmpty());
+        String sessionExpiredText = $("a").first().getText();
+        Assert.assertEquals(
+                "Unexpected view after navigation with closed session",
+                "My link", sessionExpiredText);
+
+        asserNoErrors();
+    }
+
+    private void asserNoErrors() {
+        checkLogsForErrors(msg -> msg.contains("VAADIN/static/client"));
+    }
+
+}
diff --git a/flow-tests/test-root-context/src/test/java/com/vaadin/flow/uitest/ui/dependencies/DynamicDependencyIT.java b/flow-tests/test-root-context/src/test/java/com/vaadin/flow/uitest/ui/dependencies/DynamicDependencyIT.java
index b27ed9b94c1..822c041fbf5 100644
--- a/flow-tests/test-root-context/src/test/java/com/vaadin/flow/uitest/ui/dependencies/DynamicDependencyIT.java
+++ b/flow-tests/test-root-context/src/test/java/com/vaadin/flow/uitest/ui/dependencies/DynamicDependencyIT.java
@@ -15,10 +15,15 @@
  */
 package com.vaadin.flow.uitest.ui.dependencies;
 
+import java.util.List;
+import java.util.logging.Level;
+
+import org.hamcrest.Matchers;
 import org.junit.Assert;
 import org.junit.Test;
 import org.openqa.selenium.By;
 import org.openqa.selenium.WebElement;
+import org.openqa.selenium.logging.LogEntry;
 
 import com.vaadin.flow.testutil.ChromeBrowserTest;
 
@@ -32,4 +37,38 @@ public void dynamicDependencyIsExecutedBeforeOtherMessageProcessing() {
         // true means that the added component (a new one) is not yet in the DOM
         Assert.assertEquals(Boolean.TRUE.toString(), depElement.getText());
     }
+
+    @Test
+    public void dependecyIsNoPromise_errorLogged() {
+        testErrorCase("nopromise", "result is not a Promise");
+    }
+
+    @Test
+    public void dependecyLoaderThrows_errorLogged()
+            throws InterruptedException {
+        testErrorCase("throw", "Throw on purpose");
+    }
+
+    @Test
+    public void dependecyLoaderRejects_errorLogged()
+            throws InterruptedException {
+        testErrorCase("reject", "Reject on purpose");
+    }
+
+    private void testErrorCase(String caseName, String errorMessageSnippet) {
+        open();
+
+        findElement(By.id(caseName)).click();
+
+        String statusText = findElement(By.id("new-component")).getText();
+        Assert.assertEquals("Div updated for " + caseName, statusText);
+
+        List entries = getLogEntries(Level.SEVERE);
+        Assert.assertEquals(2, entries.size());
+
+        Assert.assertThat(entries.get(0).getMessage(),
+                Matchers.containsString(errorMessageSnippet));
+        Assert.assertThat(entries.get(1).getMessage(),
+                Matchers.containsString("could not be loaded"));
+    }
 }
diff --git a/flow-tests/test-root-context/src/test/java/com/vaadin/flow/uitest/ui/template/EventHandlerIT.java b/flow-tests/test-root-context/src/test/java/com/vaadin/flow/uitest/ui/template/EventHandlerIT.java
index 0d76d80c076..285475a6ecd 100644
--- a/flow-tests/test-root-context/src/test/java/com/vaadin/flow/uitest/ui/template/EventHandlerIT.java
+++ b/flow-tests/test-root-context/src/test/java/com/vaadin/flow/uitest/ui/template/EventHandlerIT.java
@@ -63,5 +63,20 @@ public void handleEventOnServer() {
                 "Overridden server event was invoked with result: ClientSide handler",
                 findElement(By.id("overridden-event-handler-result"))
                         .getText());
+
+        // @ClientCallable return value
+        template.$("button").id("client").click();
+        Assert.assertEquals("Server-side message should be present",
+                "Call from client, message: foo, true",
+                $("div").id("client-call").getText());
+        Assert.assertEquals(
+                "Message from awaiting return value should be present", "FOO",
+                template.$("span").id("status").getText());
+
+        template.$("button").id("clientError").click();
+        Assert.assertEquals(
+                "Message from awaiting exception should be present",
+                "Error: Something went wrong. Check server-side logs for more information.",
+                template.$("span").id("status").getText());
     }
 }
diff --git a/pom.xml b/pom.xml
index 7ab278dd88d..20343f30a43 100644
--- a/pom.xml
+++ b/pom.xml
@@ -701,7 +701,6 @@
                 flow-test-util
                 flow-tests
                 flow-server-production-mode
-                flow-component-demo-helpers
                 build-tools