fix(cdk/testing): propagate task state to child environments

When creating a harness via `harnessForFixture`, we await `environment.forceStabilize()` before creating the component harness and its child environment. In newer versions of Safari, resuming from native `await` can escape the test zone back to the root zone. This caused child environments created afterwards to fail the `isInProxyZone()` check and omit `_taskState`, preventing `waitForTasksOutsideAngular` from tracking async tasks scheduled outside Angular.

These changes resolve the issue by propagating the task state from the parent `TestbedHarnessEnvironment` down to child environments created via `createEnvironment`.

Author: crisbeto

goldens/cdk/testing/testbed/index.api.md

@@ -6,13 +6,14 @@
 
 import { ComponentFixture } from '@angular/core/testing';
 import { DirectiveFixture } from '@angular/core/testing';
+import { Observable } from 'rxjs';
 
 // @public
 export type Fixture<T = unknown> = ComponentFixture<T> | DirectiveFixture<T>;
 
 // @public
 export class TestbedHarnessEnvironment extends HarnessEnvironment<Element> {
-    protected constructor(rawRootElement: Element, _fixture: Fixture, options?: TestbedHarnessEnvironmentOptions);
+    protected constructor(rawRootElement: Element, _fixture: Fixture, options?: TestbedHarnessEnvironmentOptions, taskState?: Observable<TaskState>);
     protected createEnvironment(element: Element): HarnessEnvironment<Element>;
     protected createTestElement(element: Element): TestElement;
     static documentRootLoader(fixture: Fixture, options?: TestbedHarnessEnvironmentOptions): HarnessLoader;

src/cdk/testing/testbed/task-state-zone-interceptor.ts

@@ -30,18 +30,17 @@ type PatchedProxyZone = ProxyZone & {
  * This serves as a workaround for https://github.com/angular/angular/issues/32896.
  */
 export class TaskStateZoneInterceptor {
-  private _lastState: HasTaskState | null = null;
-
   /** Subject that can be used to emit a new state change. */
-  private readonly _stateSubject = new BehaviorSubject<TaskState>(
-    this._lastState ? this._getTaskStateFromInternalZoneState(this._lastState) : {stable: true},
-  );
+  private readonly _stateSubject: BehaviorSubject<TaskState>;
 
   /** Public observable that emits whenever the task state changes. */
-  readonly state: Observable<TaskState> = this._stateSubject;
+  readonly state: Observable<TaskState>;
 
   constructor(lastState: HasTaskState | null) {
-    this._lastState = lastState;
+    this._stateSubject = new BehaviorSubject<TaskState>(
+      lastState ? this._getTaskStateFromInternalZoneState(lastState) : {stable: true},
+    );
+    this.state = this._stateSubject;
   }
 
   /** This will be called whenever the task state changes in the intercepted zone. */

src/cdk/testing/testbed/testbed-harness-environment.ts

@@ -106,10 +106,13 @@ export class TestbedHarnessEnvironment extends HarnessEnvironment<Element> {
     rawRootElement: Element,
     private _fixture: Fixture,
     options?: TestbedHarnessEnvironmentOptions,
+    taskState?: Observable<TaskState>,
   ) {
     super(rawRootElement);
     this._options = {...defaultEnvironmentOptions, ...options};
-    if (TaskStateZoneInterceptor.isInProxyZone()) {
+    if (taskState) {
+      this._taskState = taskState;
+    } else if (TaskStateZoneInterceptor.isInProxyZone()) {
       this._taskState = TaskStateZoneInterceptor.setup();
     }
     this._stabilizeCallback = () => this.forceStabilize();
@@ -219,7 +222,7 @@ export class TestbedHarnessEnvironment extends HarnessEnvironment<Element> {
 
   /** Creates a `HarnessLoader` rooted at the given raw element. */
   protected createEnvironment(element: Element): HarnessEnvironment<Element> {
-    return new TestbedHarnessEnvironment(element, this._fixture, this._options);
+    return new TestbedHarnessEnvironment(element, this._fixture, this._options, this._taskState);
   }
 
   /**