fix(bottom-sheet): DOM nodes not cleaned up if view container is destroyed mid-animation (#16349)

Along the same lines as #16309.

Currently the bottom sheet's cleanup logic is tied to its exit animation completing. This usually isn't a problem since by default the bottom sheet is attached to the application ref, however if the consumer has set a viewContainerRef and that ref is destroyed mid-animation, the exit animation event will never fire. These changes add a timeout as a fallback in case the animation doesn't finish in the specified time.

src/material/bottom-sheet/bottom-sheet-ref.ts

@@ -39,6 +39,9 @@ export class MatBottomSheetRef<T = any, R = any> {
   /** Result to be passed down to the `afterDismissed` stream. */
   private _result: R | undefined;
 
+  /** Handle to the timeout that's running as a fallback in case the exit animation doesn't fire. */
+  private _closeFallbackTimeout: number;
+
   constructor(
     containerInstance: MatBottomSheetContainer,
     private _overlayRef: OverlayRef,
@@ -61,6 +64,7 @@ export class MatBottomSheetRef<T = any, R = any> {
     containerInstance._animationStateChanged
         .pipe(filter(event => event.phaseName === 'done' && event.toState === 'hidden'), take(1))
         .subscribe(() => {
+          clearTimeout(this._closeFallbackTimeout);
           _overlayRef.dispose();
         });
 
@@ -91,7 +95,18 @@ export class MatBottomSheetRef<T = any, R = any> {
       this.containerInstance._animationStateChanged.pipe(
         filter(event => event.phaseName === 'start'),
         take(1)
-      ).subscribe(() => this._overlayRef.detachBackdrop());
+      ).subscribe(event => {
+        // The logic that disposes of the overlay depends on the exit animation completing, however
+        // it isn't guaranteed if the parent view is destroyed while it's running. Add a fallback
+        // timeout which will clean everything up if the animation hasn't fired within the specified
+        // amount of time plus 100ms. We don't need to run this outside the NgZone, because for the
+        // vast majority of cases the timeout will have been cleared before it has fired.
+        this._closeFallbackTimeout = setTimeout(() => {
+          this._overlayRef.dispose();
+        }, event.totalTime + 100);
+
+        this._overlayRef.detachBackdrop();
+      });
 
       this._result = result;
       this.containerInstance.exit();

src/material/bottom-sheet/bottom-sheet.spec.ts

@@ -192,6 +192,18 @@ describe('MatBottomSheet', () => {
     expect(overlayContainerElement.querySelector('mat-bottom-sheet-container')).toBeFalsy();
   }));
 
+  it('should dispose of bottom sheet if view container is destroyed while animating',
+    fakeAsync(() => {
+      const bottomSheetRef = bottomSheet.open(PizzaMsg, {viewContainerRef: testViewContainerRef});
+
+      bottomSheetRef.dismiss();
+      viewContainerFixture.detectChanges();
+      viewContainerFixture.destroy();
+      flush();
+
+      expect(overlayContainerElement.querySelector('mat-dialog-container')).toBeNull();
+    }));
+
   it('should emit the backdropClick stream when clicking on the overlay backdrop', fakeAsync(() => {
     const bottomSheetRef = bottomSheet.open(PizzaMsg, {viewContainerRef: testViewContainerRef});
     const spy = jasmine.createSpy('backdropClick spy');