fix(snack-bar): clean up element when associated viewContainer is destroyed

src/lib/snack-bar/snack-bar-container.ts

@@ -8,7 +8,8 @@ import {
   transition,
   animate,
   AnimationTransitionEvent,
-  NgZone
+  NgZone,
+  OnDestroy,
 } from '@angular/core';
 import {
   BasePortalHost,
@@ -53,7 +54,7 @@ export const HIDE_ANIMATION = '195ms cubic-bezier(0.0,0.0,0.2,1)';
     ])
   ],
 })
-export class MdSnackBarContainer extends BasePortalHost {
+export class MdSnackBarContainer extends BasePortalHost implements OnDestroy {
   /** The portal host inside of this container into which the snack bar content will be loaded. */
   @ViewChild(PortalHostDirective) _portalHost: PortalHostDirective;
 
@@ -87,12 +88,6 @@ export class MdSnackBarContainer extends BasePortalHost {
     throw Error('Not yet implemented');
   }
 
-  /** Begin animation of the snack bar exiting from view. */
-  exit(): Observable<void> {
-    this.animationState = 'complete';
-    return this.onExit.asObservable();
-  }
-
   /** Handle end of animations, updating the state of the snackbar. */
   onAnimationEnd(event: AnimationTransitionEvent) {
     if (event.toState === 'void' || event.toState === 'complete') {
@@ -116,6 +111,28 @@ export class MdSnackBarContainer extends BasePortalHost {
 
   /** Returns an observable resolving when the enter animation completes.  */
   _onEnter(): Observable<void> {
+    this.animationState = 'visible';
     return this.onEnter.asObservable();
   }
+
+  /** Begin animation of the snack bar exiting from view. */
+  exit(): Observable<void> {
+    this.animationState = 'complete';
+    return this._onExit();
+  }
+
+  /** Returns an observable that completes after the closing animation is done. */
+  _onExit(): Observable<void> {
+    return this.onExit.asObservable();
+  }
+
+  /** Makes sure the exit callbacks have been invoked when the element is destroyed. */
+  ngOnDestroy() {
+    // Wait for the zone to settle before removing the element. Helps prevent
+    // errors where we end up removing an element which is in the middle of an animation.
+    this._ngZone.onMicrotaskEmpty.first().subscribe(() => {
+      this.onExit.next();
+      this.onExit.complete();
+    });
+  }
 }

src/lib/snack-bar/snack-bar-ref.ts

@@ -33,16 +33,13 @@ export class MdSnackBarRef<T> {
     this.containerInstance = containerInstance;
     // Dismiss snackbar on action.
     this.onAction().subscribe(() => this.dismiss());
+    containerInstance._onExit().subscribe(() => this._finishDismiss());
   }
 
   /** Dismisses the snack bar. */
   dismiss(): void {
     if (!this._afterClosed.closed) {
-      this.containerInstance.exit().subscribe(() => {
-        this._overlayRef.dispose();
-        this._afterClosed.next();
-        this._afterClosed.complete();
-      });
+      this.containerInstance.exit();
     }
   }
 
@@ -62,6 +59,13 @@ export class MdSnackBarRef<T> {
     }
   }
 
+  /** Cleans up the DOM after closing. */
+  private _finishDismiss(): void {
+    this._overlayRef.dispose();
+    this._afterClosed.next();
+    this._afterClosed.complete();
+  }
+
   /** Gets an observable that is notified when the snack bar is finished closing. */
   afterDismissed(): Observable<void> {
     return this._afterClosed.asObservable();

src/lib/snack-bar/snack-bar.spec.ts

@@ -8,6 +8,7 @@ import {
   tick,
 } from '@angular/core/testing';
 import {NgModule, Component, Directive, ViewChild, ViewContainerRef} from '@angular/core';
+import {CommonModule} from '@angular/common';
 import {MdSnackBar, MdSnackBarModule} from './snack-bar';
 import {MdSnackBarConfig} from './snack-bar-config';
 import {OverlayContainer, MdLiveAnnouncer} from '../core';
@@ -151,6 +152,20 @@ describe('MdSnackBar', () => {
     });
   }));
 
+  it('should clean itself up when the view container gets destroyed', async(() => {
+    snackBar.open(simpleMessage, null, { viewContainerRef: testViewContainerRef });
+    viewContainerFixture.detectChanges();
+    expect(overlayContainerElement.childElementCount).toBeGreaterThan(0);
+
+    viewContainerFixture.componentInstance.childComponentExists = false;
+    viewContainerFixture.detectChanges();
+
+    viewContainerFixture.whenStable().then(() => {
+      expect(overlayContainerElement.childElementCount)
+          .toBe(0, 'Expected snack bar to be removed after the view container was destroyed');
+    });
+  }));
+
   it('should open a custom component', () => {
     let config = {viewContainerRef: testViewContainerRef};
     let snackBarRef = snackBar.openFromComponent(BurritosNotification, config);
@@ -314,11 +329,13 @@ class DirectiveWithViewContainer {
 
 @Component({
   selector: 'arbitrary-component',
-  template: `<dir-with-view-container></dir-with-view-container>`,
+  template: `<dir-with-view-container *ngIf="childComponentExists"></dir-with-view-container>`,
 })
 class ComponentWithChildViewContainer {
   @ViewChild(DirectiveWithViewContainer) childWithViewContainer: DirectiveWithViewContainer;
 
+  childComponentExists: boolean = true;
+
   get childViewContainer() {
     return this.childWithViewContainer.viewContainerRef;
   }
@@ -337,7 +354,7 @@ const TEST_DIRECTIVES = [ComponentWithChildViewContainer,
                          BurritosNotification,
                          DirectiveWithViewContainer];
 @NgModule({
-  imports: [MdSnackBarModule],
+  imports: [CommonModule, MdSnackBarModule],
   exports: TEST_DIRECTIVES,
   declarations: TEST_DIRECTIVES,
   entryComponents: [ComponentWithChildViewContainer, BurritosNotification],