Allow specify custom theme version to solve browser cache issues

[Emmenemoi]

When modifying custom themes between app releases, browser cache prevent loading the latest version which could mess a lot the vaadin app.
Same thing for widgetset generated JS if the app embed modified custom widgets.
To solve this we should be able to programmatically setup application version and/or theme version so that vaadinBootstrap.js tells the browser to download the latest versions.

For example for theme:
You could replace line 233 in vaadinBootstrap.js:

loadTheme(themeUri, versionInfo && versionInfo['vaadinVersion']);

with

if (versionInfo && versionInfo['themeVersion'])
    loadTheme(themeUri, versionInfo['themeVersion']);
else
    loadTheme(themeUri, versionInfo && versionInfo['vaadinVersion']);

And allow to programmatically set themeVersion somewhere (SystemVersionsProvider like SystemMessagesProvider ?)

For widgetset we could use applicationVersion within versionInfo object.

[Emmenemoi]

Full modifications needed:

• replace line 233 in vaadinBootstrap.js:

               var themeVersion = versionInfo && versionInfo['vaadinVersion'];
                if (versionInfo && versionInfo['appVersion']) {
                	themeVersion = versionInfo['appVersion'];
                }
                loadTheme(themeUri, themeVersion);

• add in the UIState an appVersion ou themeVersion property and setup the value:

            String appVersion = getClass().getPackage().getImplementationVersion();
            if (state.appVersion == null) {
                Properties prop = new Properties();
                try {
                    prop.load(VaadinServlet.getCurrent().getServletContext().getResourceAsStream("/META-INF/MANIFEST.MF"));
                    state.appVersion = prop.getProperty("Implementation-Version");
                } catch (IOException e) {
                    LoggerFactory.getLogger(UIState.class).error(e.toString());
                }
            }

• in DeploymentConfiguration add method:

String getAppVersion();

• in DefaultDeploymentConfiguration, setup version:

@Override
    public String getAppVersion() {
        if (appVersion == null) {
            appVersion = getClass().getPackage().getImplementationVersion();
            if (appVersion == null) {
                Properties prop = new Properties();
                try {
                    prop.load(VaadinServlet.getCurrent().getServletContext().getResourceAsStream("/META-INF/MANIFEST.MF"));
                    appVersion = prop.getProperty("Implementation-Version");
                } catch (IOException e) {
                    getLogger().warning(e.toString());
                }
            }
            // fallback to empty version
            if (appVersion == null) {
                appVersion = "";
            }
        }
        return appVersion;
    }

• add in UI constructor:
  getState().appVersion = getSession().getService().getDeploymentConfiguration().getAppVersion();
• in BootstrapHanndler:

           String appVersion = context.getSession().getService().getDeploymentConfiguration().getAppVersion();
        if (appVersion != null && !appVersion.isEmpty()) {
            versionInfo.put("appVersion", appVersion);
        }

[Emmenemoi]

Patch file against 8.8:

diff --git a/client/src/main/java/com/vaadin/client/ui/ui/UIConnector.java b/client/src/main/java/com/vaadin/client/ui/ui/UIConnector.java
index 5630cfab3c..eece929560 100644
--- a/client/src/main/java/com/vaadin/client/ui/ui/UIConnector.java
+++ b/client/src/main/java/com/vaadin/client/ui/ui/UIConnector.java
@@ -1163,7 +1163,11 @@ public class UIConnector extends AbstractSingleComponentContainerConnector
                .translateVaadinUri(ApplicationConstants.VAADIN_PROTOCOL_PREFIX
                        + "themes/" + theme + "/styles" + ".css");
        // Parameter appended to bypass caches after version upgrade.
-        themeUrl += "?v=" + Version.getFullVersion();
+        String version = Version.getFullVersion();
+        if (getState().appVersion != null && !getState().appVersion.isEmpty()) {
+            version = getState().appVersion;
+        }
+        themeUrl += "?v=" + version;
        return themeUrl;

    }
diff --git a/server/src/main/java/com/vaadin/server/BootstrapHandler.java b/server/src/main/java/com/vaadin/server/BootstrapHandler.java
index 8f52b67085..351dd961a4 100644
--- a/server/src/main/java/com/vaadin/server/BootstrapHandler.java
+++ b/server/src/main/java/com/vaadin/server/BootstrapHandler.java
@@ -781,6 +781,11 @@ public abstract class BootstrapHandler extends SynchronizedRequestHandler {
            versionInfo.put("atmosphereVersion", atmosphereVersion);
        }

+        String appVersion = context.getSession().getService().getDeploymentConfiguration().getAppVersion();
+        if (appVersion != null && !appVersion.isEmpty()) {
+            versionInfo.put("appVersion", appVersion);
+        }
+
        appConfig.put("versionInfo", versionInfo);

        WidgetsetInfo widgetsetInfo = context.getWidgetsetInfo();
diff --git a/server/src/main/java/com/vaadin/server/DefaultDeploymentConfiguration.java b/server/src/main/java/com/vaadin/server/DefaultDeploymentConfiguration.java
index 20cb001e5c..8a8145af54 100644
--- a/server/src/main/java/com/vaadin/server/DefaultDeploymentConfiguration.java
+++ b/server/src/main/java/com/vaadin/server/DefaultDeploymentConfiguration.java
@@ -16,11 +16,13 @@

package com.vaadin.server;

+import java.io.Exception;
import java.util.Locale;
import java.util.Properties;
import java.util.logging.Logger;

import com.vaadin.shared.communication.PushMode;
+import com.vaadin.shared.ui.ui.UIState;

/**
 * The default implementation of {@link DeploymentConfiguration} based on a base
@@ -65,6 +67,7 @@ public class DefaultDeploymentConfiguration
    private final Class<?> systemPropertyBaseClass;
    private boolean syncIdCheck;
    private boolean sendUrlsAsParameters;
+    private String appVersion;

    /**
     * Create a new deployment configuration instance.
@@ -263,6 +266,27 @@ public class DefaultDeploymentConfiguration
        return initParameters;
    }

+    @Override
+    public String getAppVersion() {
+        if (appVersion == null) {
+            appVersion = getClass().getPackage().getImplementationVersion();
+            if (appVersion == null) {
+                Properties prop = new Properties();
+                try {
+                    prop.load(VaadinServlet.getCurrent().getServletContext().getResourceAsStream("/META-INF/MANIFEST.MF"));
+                    appVersion = prop.getProperty("Implementation-Version");
+                } catch (Exception e) {
+                    getLogger().warning(e.toString());
+                }
+            }
+            // fallback to empty version
+            if (appVersion == null) {
+                appVersion = "";
+            }
+        }
+        return appVersion;
+    }
+
    /**
     * Log a warning if Vaadin is not running in production mode.
     */
diff --git a/server/src/main/java/com/vaadin/server/DeploymentConfiguration.java b/server/src/main/java/com/vaadin/server/DeploymentConfiguration.java
index e0700742ef..1dcaaea4e6 100644
--- a/server/src/main/java/com/vaadin/server/DeploymentConfiguration.java
+++ b/server/src/main/java/com/vaadin/server/DeploymentConfiguration.java
@@ -173,4 +173,10 @@ public interface DeploymentConfiguration extends Serializable {
     */
    public String getClassLoaderName();

+    /**
+     * Gets the Vaadin app version.
+     *
+     * @since 8.8
+     */
+    public String getAppVersion();
}

diff --git a/server/src/main/java/com/vaadin/ui/UI.java b/server/src/main/java/com/vaadin/ui/UI.java
index 2a3b913e16..be04c530cd 100644
--- a/server/src/main/java/com/vaadin/ui/UI.java
+++ b/server/src/main/java/com/vaadin/ui/UI.java
@@ -22,14 +22,7 @@ import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.lang.reflect.Method;
import java.net.URI;
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.Iterator;
-import java.util.LinkedHashMap;
-import java.util.LinkedHashSet;
-import java.util.List;
-import java.util.Map;
+import java.util.*;
import java.util.Map.Entry;
import java.util.concurrent.Future;
import java.util.logging.Level;
@@ -328,6 +321,7 @@ public abstract class UI extends AbstractSingleComponentContainer
        registerRpc(windowOrderRpc);
        setSizeFull();
        setContent(content);
+        getState().appVersion = getSession().getService().getDeploymentConfiguration().getAppVersion();
    }


diff --git a/server/src/main/resources/VAADIN/vaadinBootstrap.js b/server/src/main/resources/VAADIN/vaadinBootstrap.js
index a6830f434b..93b53d9e4d 100644
--- a/server/src/main/resources/VAADIN/vaadinBootstrap.js
+++ b/server/src/main/resources/VAADIN/vaadinBootstrap.js
@@ -230,7 +230,11 @@
                var versionInfo = getConfig('versionInfo');

                var themeUri = vaadinDir + 'themes/' + getConfig('theme');
-                loadTheme(themeUri, versionInfo && versionInfo['vaadinVersion']);
+                var themeVersion = versionInfo && versionInfo['vaadinVersion'];
+                if (versionInfo && versionInfo['appVersion']) {
+                	themeVersion = versionInfo['appVersion'];
+                }
+                loadTheme(themeUri, themeVersion);

                var widgetset = getConfig('widgetset');
                var widgetsetUrl = getConfig('widgetsetUrl');
diff --git a/shared/src/main/java/com/vaadin/shared/ui/ui/UIState.java b/shared/src/main/java/com/vaadin/shared/ui/ui/UIState.java
index 90269a8b09..c784e732da 100644
--- a/shared/src/main/java/com/vaadin/shared/ui/ui/UIState.java
+++ b/shared/src/main/java/com/vaadin/shared/ui/ui/UIState.java
@@ -79,6 +79,14 @@ public class UIState extends AbstractSingleComponentContainerState {
     * @since 7.3
     */
    public String theme;
+
+    /**
+     * Used for cache detection
+     *
+     * @since 8.5
+     */
+    public String appVersion;
+
    public ReconnectDialogConfigurationState reconnectDialogConfiguration = new ReconnectDialogConfigurationState();
    {
        primaryStyleName = "v-ui";

[Emmenemoi]

up. This is very annoying for the users: they must manually clear the cache.