test(core): verify `onDestroy` callbacks are invoked when ComponentRef is destroyed (#39876)

This commit adds a few tests to verify that the `onDestroy` callbacks are invoked when `ComponentRef` instance
is destroyed and the logic is consistent between ViewEngine and Ivy.

PR Close #39876

packages/core/src/application_ref.ts

@@ -804,7 +804,6 @@ export class ApplicationRef {
 
   /** @internal */
   ngOnDestroy() {
-    // TODO(alxhub): Dispose of the NgZone.
     this._views.slice().forEach((view) => view.destroy());
     this._onMicrotaskEmptySubscription.unsubscribe();
   }

packages/core/test/acceptance/bootstrap_spec.ts

@@ -6,7 +6,8 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {COMPILER_OPTIONS, Component, destroyPlatform, NgModule, ViewEncapsulation} from '@angular/core';
+import {ApplicationRef, COMPILER_OPTIONS, Component, destroyPlatform, NgModule, TestabilityRegistry, ViewEncapsulation} from '@angular/core';
+import {expect} from '@angular/core/testing/src/testing_internal';
 import {BrowserModule} from '@angular/platform-browser';
 import {platformBrowserDynamic} from '@angular/platform-browser-dynamic';
 import {onlyInIvy, withBody} from '@angular/private/testing';
@@ -151,6 +152,81 @@ describe('bootstrap', () => {
          ngModuleRef.destroy();
        }));
 
+    describe('ApplicationRef cleanup', () => {
+      it('should cleanup ApplicationRef when Injector is destroyed',
+         withBody('<my-app></my-app>', async () => {
+           const TestModule = createComponentAndModule();
+
+           const ngModuleRef = await platformBrowserDynamic().bootstrapModule(TestModule);
+           const appRef = ngModuleRef.injector.get(ApplicationRef);
+           const testabilityRegistry = ngModuleRef.injector.get(TestabilityRegistry);
+
+           expect(appRef.components.length).toBe(1);
+           expect(testabilityRegistry.getAllRootElements().length).toBe(1);
+
+           ngModuleRef.destroy();  // also destroys an Injector instance.
+
+           expect(appRef.components.length).toBe(0);
+           expect(testabilityRegistry.getAllRootElements().length).toBe(0);
+         }));
+
+      it('should cleanup ApplicationRef when ComponentRef is destroyed',
+         withBody('<my-app></my-app>', async () => {
+           const TestModule = createComponentAndModule();
+
+           const ngModuleRef = await platformBrowserDynamic().bootstrapModule(TestModule);
+           const appRef = ngModuleRef.injector.get(ApplicationRef);
+           const testabilityRegistry = ngModuleRef.injector.get(TestabilityRegistry);
+           const componentRef = appRef.components[0];
+
+           expect(appRef.components.length).toBe(1);
+           expect(testabilityRegistry.getAllRootElements().length).toBe(1);
+
+           componentRef.destroy();
+
+           expect(appRef.components.length).toBe(0);
+           expect(testabilityRegistry.getAllRootElements().length).toBe(0);
+         }));
+
+      it('should not throw in case ComponentRef is destroyed and Injector is destroyed after that',
+         withBody('<my-app></my-app>', async () => {
+           const TestModule = createComponentAndModule();
+
+           const ngModuleRef = await platformBrowserDynamic().bootstrapModule(TestModule);
+           const appRef = ngModuleRef.injector.get(ApplicationRef);
+           const testabilityRegistry = ngModuleRef.injector.get(TestabilityRegistry);
+           const componentRef = appRef.components[0];
+
+           expect(appRef.components.length).toBe(1);
+           expect(testabilityRegistry.getAllRootElements().length).toBe(1);
+
+           componentRef.destroy();
+           ngModuleRef.destroy();  // also destroys an Injector instance.
+
+           expect(appRef.components.length).toBe(0);
+           expect(testabilityRegistry.getAllRootElements().length).toBe(0);
+         }));
+
+      it('should not throw in case Injector is destroyed and ComponentRef is destroyed after that',
+         withBody('<my-app></my-app>', async () => {
+           const TestModule = createComponentAndModule();
+
+           const ngModuleRef = await platformBrowserDynamic().bootstrapModule(TestModule);
+           const appRef = ngModuleRef.injector.get(ApplicationRef);
+           const testabilityRegistry = ngModuleRef.injector.get(TestabilityRegistry);
+           const componentRef = appRef.components[0];
+
+           expect(appRef.components.length).toBe(1);
+           expect(testabilityRegistry.getAllRootElements().length).toBe(1);
+
+           ngModuleRef.destroy();  // also destroys an Injector instance.
+           componentRef.destroy();
+
+           expect(appRef.components.length).toBe(0);
+           expect(testabilityRegistry.getAllRootElements().length).toBe(0);
+         }));
+    });
+
     onlyInIvy('options cannot be changed in Ivy').describe('changing bootstrap options', () => {
       beforeEach(() => {
         spyOn(console, 'error');

packages/core/test/acceptance/component_spec.ts

@@ -303,6 +303,57 @@ describe('component', () => {
        expect(wrapperEls.length).toBe(2);  // other elements are preserved
      });
 
+  it('should invoke `onDestroy` callbacks of dynamically created component', () => {
+    let wasOnDestroyCalled = false;
+    @Component({
+      selector: '[comp]',
+      template: 'comp content',
+    })
+    class DynamicComponent {
+    }
+
+    @NgModule({
+      declarations: [DynamicComponent],
+      entryComponents: [DynamicComponent],  // needed only for ViewEngine
+    })
+    class TestModule {
+    }
+
+    @Component({
+      selector: 'button',
+      template: '<div id="app-root" #anchor></div>',
+    })
+    class App {
+      @ViewChild('anchor', {read: ViewContainerRef}) anchor!: ViewContainerRef;
+
+      constructor(private cfr: ComponentFactoryResolver, private injector: Injector) {}
+
+      create() {
+        const factory = this.cfr.resolveComponentFactory(DynamicComponent);
+        const componentRef = factory.create(this.injector);
+        componentRef.onDestroy(() => {
+          wasOnDestroyCalled = true;
+        });
+        this.anchor.insert(componentRef.hostView);
+      }
+
+      clear() {
+        this.anchor.clear();
+      }
+    }
+
+    TestBed.configureTestingModule({imports: [TestModule], declarations: [App]});
+    const fixture = TestBed.createComponent(App);
+    fixture.detectChanges();
+
+    // Add ComponentRef to ViewContainerRef instance.
+    fixture.componentInstance.create();
+    // Clear ViewContainerRef to invoke `onDestroy` callbacks on ComponentRef.
+    fixture.componentInstance.clear();
+
+    expect(wasOnDestroyCalled).toBeTrue();
+  });
+
   describe('invalid host element', () => {
     it('should throw when <ng-container> is used as a host element for a Component', () => {
       @Component({