feat(ivy): support checkNoChanges (angular#22710)

PR Close angular#22710

Author: kara

packages/core/src/render3/instructions.ts

@@ -151,6 +151,13 @@ let bindingIndex: number;
  */
 let cleanup: any[]|null;
 
+/**
+ * In this mode, any changes in bindings will throw an ExpressionChangedAfterChecked error.
+ *
+ * Necessary to support ChangeDetectorRef.checkNoChanges().
+ */
+let checkNoChangesMode = false;
+
 const enum BindingDirection {
   Input,
   Output,
@@ -194,9 +201,11 @@ export function enterView(newView: LView, host: LElementNode | LViewNode | null)
  * the direction of traversal (up or down the view tree) a bit clearer.
  */
 export function leaveView(newView: LView): void {
-  executeHooks(
-      currentView.data, currentView.tView.viewHooks, currentView.tView.viewCheckHooks,
-      creationMode);
+  if (!checkNoChangesMode) {
+    executeHooks(
+        currentView.data, currentView.tView.viewHooks, currentView.tView.viewCheckHooks,
+        creationMode);
+  }
   // Views should be clean and in update mode after being checked, so these bits are cleared
   currentView.flags &= ~(LViewFlags.CreationMode | LViewFlags.Dirty);
   currentView.lifecycleStage = LifecycleStage.INIT;
@@ -1135,9 +1144,11 @@ export function containerRefreshStart(index: number): void {
                    (previousOrParentNode as LContainerNode).native, undefined,
                    `the container's native element should not have been set yet.`);
 
-  // We need to execute init hooks here so ngOnInit hooks are called in top level views
-  // before they are called in embedded views (for backwards compatibility).
-  executeInitHooks(currentView, currentView.tView, creationMode);
+  if (!checkNoChangesMode) {
+    // We need to execute init hooks here so ngOnInit hooks are called in top level views
+    // before they are called in embedded views (for backwards compatibility).
+    executeInitHooks(currentView, currentView.tView, creationMode);
+  }
 }
 
 /**
@@ -1270,8 +1281,10 @@ export function embeddedViewEnd(): void {
  * @param elementIndex
  */
 export function directiveRefresh<T>(directiveIndex: number, elementIndex: number): void {
-  executeInitHooks(currentView, currentView.tView, creationMode);
-  executeContentHooks(currentView, currentView.tView, creationMode);
+  if (!checkNoChangesMode) {
+    executeInitHooks(currentView, currentView.tView, creationMode);
+    executeContentHooks(currentView, currentView.tView, creationMode);
+  }
   const template = (tData[directiveIndex] as ComponentDef<T>).template;
   if (template != null) {
     ngDevMode && assertDataInRange(elementIndex);
@@ -1594,6 +1607,37 @@ export function detectChanges<T>(component: T): void {
 }
 
 
+/**
+ * Checks the change detector and its children, and throws if any changes are detected.
+ *
+ * This is used in development mode to verify that running change detection doesn't
+ * introduce other changes.
+ */
+export function checkNoChanges<T>(component: T): void {
+  checkNoChangesMode = true;
+  try {
+    detectChanges(component);
+  } finally {
+    checkNoChangesMode = false;
+  }
+}
+
+/** Throws an ExpressionChangedAfterChecked error if checkNoChanges mode is on. */
+function throwErrorIfNoChangesMode(oldValue: any, currValue: any): never|void {
+  if (checkNoChangesMode) {
+    let msg =
+        `ExpressionChangedAfterItHasBeenCheckedError: Expression has changed after it was checked. Previous value: '${oldValue}'. Current value: '${currValue}'.`;
+    if (creationMode) {
+      msg +=
+          ` It seems like the view has been created after its parent and its children have been dirty checked.` +
+          ` Has it been created in a change detection hook ?`;
+    }
+    // TODO: include debug context
+    throw new Error(msg);
+  }
+}
+
+
 /** Checks the view of the component provided. Does not gate on dirty checks or execute doCheck. */
 function detectChangesInternal<T>(hostView: LView, hostNode: LElementNode, component: T) {
   const componentIndex = hostNode.flags >> LNodeFlags.INDX_SHIFT;
@@ -1672,6 +1716,7 @@ export function bind<T>(value: T | NO_CHANGE): T|NO_CHANGE {
 
   const changed: boolean = value !== NO_CHANGE && isDifferent(data[bindingIndex], value);
   if (changed) {
+    throwErrorIfNoChangesMode(data[bindingIndex], value);
     data[bindingIndex] = value;
   }
   bindingIndex++;
@@ -1841,14 +1886,17 @@ export function consumeBinding(): any {
 export function bindingUpdated(value: any): boolean {
   ngDevMode && assertNotEqual(value, NO_CHANGE, 'Incoming value should never be NO_CHANGE.');
 
-  if (creationMode || isDifferent(data[bindingIndex], value)) {
-    creationMode && initBindings();
-    data[bindingIndex++] = value;
-    return true;
+  if (creationMode) {
+    initBindings();
+  } else if (isDifferent(data[bindingIndex], value)) {
+    throwErrorIfNoChangesMode(data[bindingIndex], value);
   } else {
     bindingIndex++;
     return false;
   }
+
+  data[bindingIndex++] = value;
+  return true;
 }
 
 /** Updates binding if changed, then returns the latest value. */

packages/core/src/render3/view_ref.ts

@@ -8,7 +8,7 @@
 
 import {EmbeddedViewRef as viewEngine_EmbeddedViewRef} from '../linker/view_ref';
 
-import {detectChanges, markViewDirty} from './instructions';
+import {checkNoChanges, detectChanges, markViewDirty} from './instructions';
 import {ComponentTemplate} from './interfaces/definition';
 import {LViewNode} from './interfaces/node';
 import {LView, LViewFlags} from './interfaces/view';
@@ -195,7 +195,13 @@ export class ViewRef<T> implements viewEngine_EmbeddedViewRef<T> {
    */
   detectChanges(): void { detectChanges(this.context); }
 
-  checkNoChanges(): void { notImplemented(); }
+  /**
+   * Checks the change detector and its children, and throws if any changes are detected.
+   *
+   * This is used in development mode to verify that running change detection doesn't
+   * introduce other changes.
+   */
+  checkNoChanges(): void { checkNoChanges(this.context); }
 }
 
 

packages/core/test/bundling/hello_world/bundle.golden_symbols.json

@@ -35,6 +35,9 @@
   {
     "name": "canInsertNativeNode"
   },
+  {
+    "name": "checkNoChangesMode"
+  },
   {
     "name": "createLNode"
   },

packages/core/test/render3/change_detection_spec.ts

@@ -911,6 +911,162 @@ describe('change detection', () => {
       // TODO(kara): add test for dynamic views once bug fix is in
     });
 
+    describe('checkNoChanges', () => {
+      let comp: NoChangesComp;
+
+      class NoChangesComp {
+        value = 1;
+        doCheckCount = 0;
+        contentCheckCount = 0;
+        viewCheckCount = 0;
+
+        ngDoCheck() { this.doCheckCount++; }
+
+        ngAfterContentChecked() { this.contentCheckCount++; }
+
+        ngAfterViewChecked() { this.viewCheckCount++; }
+
+        constructor(public cdr: ChangeDetectorRef) {}
+
+        static ngComponentDef = defineComponent({
+          type: NoChangesComp,
+          tag: 'no-changes-comp',
+          factory: () => comp = new NoChangesComp(injectChangeDetectorRef()),
+          template: (ctx: NoChangesComp, cm: boolean) => {
+            if (cm) {
+              text(0);
+            }
+            textBinding(0, bind(ctx.value));
+          }
+        });
+      }
+
+      class AppComp {
+        value = 1;
+
+        constructor(public cdr: ChangeDetectorRef) {}
+
+        static ngComponentDef = defineComponent({
+          type: AppComp,
+          tag: 'app-comp',
+          factory: () => new AppComp(injectChangeDetectorRef()),
+          /**
+           * {{ value }} -
+           * <no-changes-comp></no-changes-comp>
+           */
+          template: (ctx: AppComp, cm: boolean) => {
+            if (cm) {
+              text(0);
+              elementStart(1, NoChangesComp);
+              elementEnd();
+            }
+            textBinding(0, interpolation1('', ctx.value, ' - '));
+            NoChangesComp.ngComponentDef.h(2, 1);
+            directiveRefresh(2, 1);
+          }
+        });
+      }
+
+      it('should throw if bindings in current view have changed', () => {
+        const comp = renderComponent(NoChangesComp);
+
+        expect(() => comp.cdr.checkNoChanges()).not.toThrow();
+
+        comp.value = 2;
+        expect(() => comp.cdr.checkNoChanges())
+            .toThrowError(
+                /ExpressionChangedAfterItHasBeenCheckedError: .+ Previous value: '1'. Current value: '2'/gi);
+      });
+
+      it('should throw if interpolations in current view have changed', () => {
+        const app = renderComponent(AppComp);
+
+        expect(() => app.cdr.checkNoChanges()).not.toThrow();
+
+        app.value = 2;
+        expect(() => app.cdr.checkNoChanges())
+            .toThrowError(
+                /ExpressionChangedAfterItHasBeenCheckedError: .+ Previous value: '1'. Current value: '2'/gi);
+      });
+
+      it('should throw if bindings in children of current view have changed', () => {
+        const app = renderComponent(AppComp);
+
+        expect(() => app.cdr.checkNoChanges()).not.toThrow();
+
+        comp.value = 2;
+        expect(() => app.cdr.checkNoChanges())
+            .toThrowError(
+                /ExpressionChangedAfterItHasBeenCheckedError: .+ Previous value: '1'. Current value: '2'/gi);
+      });
+
+      it('should throw if bindings in embedded view have changed', () => {
+        class EmbeddedViewApp {
+          value = 1;
+          showing = true;
+
+          constructor(public cdr: ChangeDetectorRef) {}
+
+          static ngComponentDef = defineComponent({
+            type: EmbeddedViewApp,
+            tag: 'embedded-view-app',
+            factory: () => new EmbeddedViewApp(injectChangeDetectorRef()),
+            /**
+             * % if (showing) {
+             *  {{ value }}
+             * %}
+             */
+            template: (ctx: EmbeddedViewApp, cm: boolean) => {
+              if (cm) {
+                container(0);
+              }
+              containerRefreshStart(0);
+              {
+                if (ctx.showing) {
+                  if (embeddedViewStart(0)) {
+                    text(0);
+                  }
+                  textBinding(0, bind(ctx.value));
+                  embeddedViewEnd();
+                }
+              }
+              containerRefreshEnd();
+            }
+          });
+        }
+
+        const app = renderComponent(EmbeddedViewApp);
+
+        expect(() => app.cdr.checkNoChanges()).not.toThrow();
+
+        app.value = 2;
+        expect(() => app.cdr.checkNoChanges())
+            .toThrowError(
+                /ExpressionChangedAfterItHasBeenCheckedError: .+ Previous value: '1'. Current value: '2'/gi);
+      });
+
+      it('should NOT call lifecycle hooks', () => {
+        const app = renderComponent(AppComp);
+        expect(comp.doCheckCount).toEqual(1);
+        expect(comp.contentCheckCount).toEqual(1);
+        expect(comp.viewCheckCount).toEqual(1);
+
+        comp.value = 2;
+        expect(() => app.cdr.checkNoChanges()).toThrow();
+        expect(comp.doCheckCount).toEqual(1);
+        expect(comp.contentCheckCount).toEqual(1);
+        expect(comp.viewCheckCount).toEqual(1);
+      });
+
+      it('should NOT throw if bindings in ancestors of current view have changed', () => {
+        const app = renderComponent(AppComp);
+
+        app.value = 2;
+        expect(() => comp.cdr.checkNoChanges()).not.toThrow();
+      });
+
+    });
+
   });
 
 });