fix(menu): nested menu error when items are rendered in a repeater

src/lib/menu/menu-directive.ts

@@ -10,7 +10,7 @@ import {AnimationEvent} from '@angular/animations';
 import {FocusKeyManager} from '@angular/cdk/a11y';
 import {Direction} from '@angular/cdk/bidi';
 import {ESCAPE, LEFT_ARROW, RIGHT_ARROW} from '@angular/cdk/keycodes';
-import {RxChain, startWith, switchMap} from '@angular/cdk/rxjs';
+import {RxChain, startWith, switchMap, first} from '@angular/cdk/rxjs';
 import {
   AfterContentInit,
   ChangeDetectionStrategy,
@@ -27,10 +27,12 @@ import {
   TemplateRef,
   ViewChild,
   ViewEncapsulation,
+  NgZone,
 } from '@angular/core';
 import {Observable} from 'rxjs/Observable';
 import {merge} from 'rxjs/observable/merge';
 import {Subscription} from 'rxjs/Subscription';
+import {Subject} from 'rxjs/Subject';
 import {fadeInItems, transformMenu} from './menu-animations';
 import {throwMatMenuInvalidPositionX, throwMatMenuInvalidPositionY} from './menu-errors';
 import {MatMenuItem} from './menu-item';
@@ -80,7 +82,7 @@ export class MatMenu implements AfterContentInit, MatMenuPanel, OnDestroy {
   private _tabSubscription = Subscription.EMPTY;
 
   /** Config object to be passed into the menu's ngClass */
-  _classList: any = {};
+  _classList: {[key: string]: boolean} = {};
 
   /** Current state of the panel animation. */
   _panelAnimationState: 'void' | 'enter-start' | 'enter' = 'void';
@@ -145,6 +147,7 @@ export class MatMenu implements AfterContentInit, MatMenuPanel, OnDestroy {
 
   constructor(
     private _elementRef: ElementRef,
+    private _ngZone: NgZone,
     @Inject(MAT_MENU_DEFAULT_OPTIONS) private _defaultOptions: MatMenuDefaultOptions) { }
 
   ngAfterContentInit() {
@@ -160,9 +163,16 @@ export class MatMenu implements AfterContentInit, MatMenuPanel, OnDestroy {
 
   /** Stream that emits whenever the hovered menu item changes. */
   hover(): Observable<MatMenuItem> {
-    return RxChain.from(this.items.changes)
-      .call(startWith, this.items)
-      .call(switchMap, (items: MatMenuItem[]) => merge(...items.map(item => item.hover)))
+    if (this.items) {
+      return RxChain.from(this.items.changes)
+        .call(startWith, this.items)
+        .call(switchMap, (items: MatMenuItem[]) => merge(...items.map(item => item.hover)))
+        .result();
+    }
+
+    return RxChain.from(this._ngZone.onStable.asObservable())
+      .call(first)
+      .call(switchMap, () => this.hover())
       .result();
   }
 

src/lib/menu/menu-trigger.ts

@@ -22,7 +22,7 @@ import {
 import {TemplatePortal} from '@angular/cdk/portal';
 import {filter, RxChain} from '@angular/cdk/rxjs';
 import {
-  AfterViewInit,
+  AfterContentInit,
   Directive,
   ElementRef,
   EventEmitter,
@@ -82,7 +82,7 @@ export const MENU_PANEL_TOP_PADDING = 8;
   },
   exportAs: 'matMenuTrigger'
 })
-export class MatMenuTrigger implements AfterViewInit, OnDestroy {
+export class MatMenuTrigger implements AfterContentInit, OnDestroy {
   private _portal: TemplatePortal<any>;
   private _overlayRef: OverlayRef | null = null;
   private _menuOpen: boolean = false;
@@ -126,7 +126,7 @@ export class MatMenuTrigger implements AfterViewInit, OnDestroy {
     }
   }
 
-  ngAfterViewInit() {
+  ngAfterContentInit() {
     this._checkMenu();
 
     this.menu.close.subscribe(reason => {

src/lib/menu/menu.spec.ts

@@ -48,7 +48,8 @@ describe('MatMenu', () => {
         CustomMenuPanel,
         CustomMenu,
         NestedMenu,
-        NestedMenuCustomElevation
+        NestedMenuCustomElevation,
+        NestedMenuRepeater
       ],
       providers: [
         {provide: OverlayContainer, useFactory: () => {
@@ -1029,6 +1030,21 @@ describe('MatMenu', () => {
       expect(event.preventDefault).toHaveBeenCalled();
     });
 
+    it('should handle the items being rendered in a repeater', fakeAsync(() => {
+      const repeaterFixture = TestBed.createComponent(NestedMenuRepeater);
+      overlay = overlayContainerElement;
+
+      expect(() => repeaterFixture.detectChanges()).not.toThrow();
+
+      repeaterFixture.componentInstance.rootTriggerEl.nativeElement.click();
+      repeaterFixture.detectChanges();
+      expect(overlay.querySelectorAll('.mat-menu-panel').length).toBe(1, 'Expected one open menu');
+
+      dispatchMouseEvent(overlay.querySelector('.level-one-trigger')!, 'mouseenter');
+      repeaterFixture.detectChanges();
+      expect(overlay.querySelectorAll('.mat-menu-panel').length).toBe(2, 'Expected two open menus');
+    }));
+
   });
 
 });
@@ -1223,3 +1239,28 @@ class NestedMenuCustomElevation {
   @ViewChild('rootTrigger') rootTrigger: MatMenuTrigger;
   @ViewChild('levelOneTrigger') levelOneTrigger: MatMenuTrigger;
 }
+
+
+@Component({
+  template: `
+    <button [matMenuTriggerFor]="root" #rootTriggerEl>Toggle menu</button>
+    <mat-menu #root="matMenu">
+      <button
+        mat-menu-item
+        class="level-one-trigger"
+        *ngFor="let item of items"
+        [matMenuTriggerFor]="levelOne">{{item}}</button>
+    </mat-menu>
+
+    <mat-menu #levelOne="matMenu">
+      <button mat-menu-item>Four</button>
+      <button mat-menu-item>Five</button>
+    </mat-menu>
+  `
+})
+class NestedMenuRepeater {
+  @ViewChild('rootTriggerEl') rootTriggerEl: ElementRef;
+  @ViewChild('levelOneTrigger') levelOneTrigger: MatMenuTrigger;
+
+  items = ['one', 'two', 'three'];
+}