chore(tabs): use custom portal template directive for hosting tab body content

src/lib/tabs/public-api.ts

@@ -9,11 +9,14 @@
 export * from './tabs-module';
 export * from './tab-group';
 export {MatInkBar} from './ink-bar';
-export {MatTabBody, MatTabBodyOriginState, MatTabBodyPositionState} from './tab-body';
+export {
+  MatTabBody,
+  MatTabBodyOriginState,
+  MatTabBodyPositionState,
+  MatTabBodyPortal
+} from './tab-body';
 export {MatTabHeader, ScrollDirection} from './tab-header';
 export {MatTabLabelWrapper} from './tab-label-wrapper';
 export {MatTab} from './tab';
 export {MatTabLabel} from './tab-label';
 export {MatTabNav, MatTabLink} from './tab-nav-bar/index';
-
-

src/lib/tabs/tab-body.html

@@ -2,5 +2,5 @@
      [@translateTab]="_position"
      (@translateTab.start)="_onTranslateTabStarted($event)"
      (@translateTab.done)="_onTranslateTabComplete($event)">
-  <ng-template cdkPortalOutlet></ng-template>
+  <ng-template matTabBodyHost></ng-template>
 </div>

src/lib/tabs/tab-body.spec.ts

@@ -2,10 +2,10 @@ import {Direction, Directionality} from '@angular/cdk/bidi';
 import {PortalModule, TemplatePortal} from '@angular/cdk/portal';
 import {CommonModule} from '@angular/common';
 import {Component, TemplateRef, ViewChild, ViewContainerRef} from '@angular/core';
-import {async, ComponentFixture, fakeAsync, flushMicrotasks, TestBed} from '@angular/core/testing';
+import {async, ComponentFixture, TestBed} from '@angular/core/testing';
 import {MatRippleModule} from '@angular/material/core';
 import {NoopAnimationsModule} from '@angular/platform-browser/animations';
-import {MatTabBody} from './tab-body';
+import {MatTabBody, MatTabBodyPortal} from './tab-body';
 
 
 describe('MatTabBody', () => {
@@ -17,6 +17,7 @@ describe('MatTabBody', () => {
       imports: [CommonModule, PortalModule, MatRippleModule, NoopAnimationsModule],
       declarations: [
         MatTabBody,
+        MatTabBodyPortal,
         SimpleTabBodyApp,
       ],
       providers: [
@@ -145,30 +146,6 @@ describe('MatTabBody', () => {
       expect(fixture.componentInstance.tabBody._position).toBe('left');
     });
   });
-
-  describe('on centered', () => {
-    let fixture: ComponentFixture<SimpleTabBodyApp>;
-
-    beforeEach(fakeAsync(() => {
-      fixture = TestBed.createComponent(SimpleTabBodyApp);
-    }));
-
-    it('should attach the content when centered and detach when not', fakeAsync(() => {
-      fixture.componentInstance.position = 1;
-      fixture.detectChanges();
-      expect(fixture.componentInstance.tabBody._portalOutlet.hasAttached()).toBe(false);
-
-      fixture.componentInstance.position = 0;
-      fixture.detectChanges();
-      expect(fixture.componentInstance.tabBody._portalOutlet.hasAttached()).toBe(true);
-
-      fixture.componentInstance.position = 1;
-      fixture.detectChanges();
-      flushMicrotasks(); // Finish animation and let it detach in animation done handler
-      expect(fixture.componentInstance.tabBody._portalOutlet.hasAttached()).toBe(false);
-    }));
-  });
-
 });
 
 

src/lib/tabs/tab-body.ts

@@ -7,17 +7,21 @@
  */
 
 import {
-  ViewChild,
   Component,
   Input,
+  Inject,
   Output,
   EventEmitter,
+  OnDestroy,
   OnInit,
   ElementRef,
+  Directive,
   Optional,
-  AfterViewChecked,
   ViewEncapsulation,
   ChangeDetectionStrategy,
+  ComponentFactoryResolver,
+  ViewContainerRef,
+  forwardRef,
 } from '@angular/core';
 import {
   trigger,
@@ -29,7 +33,10 @@ import {
 } from '@angular/animations';
 import {TemplatePortal, CdkPortalOutlet} from '@angular/cdk/portal';
 import {Directionality, Direction} from '@angular/cdk/bidi';
+import {Subscription} from 'rxjs/Subscription';
 
+/** Workaround for https://github.com/angular/angular/issues/17849 */
+export const _MatTabBodyPortalBaseClass = CdkPortalOutlet;
 
 /**
  * These position states are used internally as animation states for the tab body. Setting the
@@ -52,6 +59,44 @@ export type MatTabBodyPositionState =
  */
 export type MatTabBodyOriginState = 'left' | 'right';
 
+/**
+ * The portal host directive for the contents of the tab.
+ * @docs-private
+ */
+@Directive({
+  selector: '[matTabBodyHost]'
+})
+export class MatTabBodyPortal extends _MatTabBodyPortalBaseClass implements OnInit, OnDestroy {
+  /** A subscription to events for when the tab body begins centering. */
+  private _centeringSub: Subscription;
+
+  constructor(
+    _componentFactoryResolver: ComponentFactoryResolver,
+    _viewContainerRef: ViewContainerRef,
+    @Inject(forwardRef(() => MatTabBody)) private _host: MatTabBody) {
+      super(_componentFactoryResolver, _viewContainerRef);
+  }
+
+  /** Set initial visibility or set up subscription for changing visibility. */
+  ngOnInit(): void {
+    if (this._host._isCenterPosition(this._host._position)) {
+      this.attach(this._host._content);
+    } else {
+      this._centeringSub = this._host._beforeCentering.subscribe(() => {
+        this.attach(this._host._content);
+        this._centeringSub.unsubscribe();
+      });
+    }
+  }
+
+  /** Clean up subscription if necessary. */
+  ngOnDestroy(): void {
+    if (this._centeringSub && !this._centeringSub.closed) {
+      this._centeringSub.unsubscribe();
+    }
+  }
+}
+
 /**
  * Wrapper for the contents of a tab.
  * @docs-private
@@ -86,13 +131,13 @@ export type MatTabBodyOriginState = 'left' | 'right';
     ])
   ]
 })
-export class MatTabBody implements OnInit, AfterViewChecked {
-  /** The portal outlet inside of this container into which the tab body content will be loaded. */
-  @ViewChild(CdkPortalOutlet) _portalOutlet: CdkPortalOutlet;
-
+export class MatTabBody implements OnInit {
   /** Event emitted when the tab begins to animate towards the center as the active tab. */
   @Output() _onCentering: EventEmitter<number> = new EventEmitter<number>();
 
+  /** Event emitted before the centering of the tab begins. */
+  @Output() _beforeCentering: EventEmitter<number> = new EventEmitter<number>();
+
   /** Event emitted when the tab completes its animation towards the center. */
   @Output() _onCentered: EventEmitter<void> = new EventEmitter<void>(true);
 
@@ -139,28 +184,14 @@ export class MatTabBody implements OnInit, AfterViewChecked {
     }
   }
 
-  /**
-   * After the view has been set, check if the tab content is set to the center and attach the
-   * content if it is not already attached.
-   */
-  ngAfterViewChecked() {
-    if (this._isCenterPosition(this._position) && !this._portalOutlet.hasAttached()) {
-      this._portalOutlet.attach(this._content);
-    }
-  }
-
-  _onTranslateTabStarted(e: AnimationEvent) {
+  _onTranslateTabStarted(e: AnimationEvent): void {
     if (this._isCenterPosition(e.toState)) {
+      this._beforeCentering.emit();
       this._onCentering.emit(this._elementRef.nativeElement.clientHeight);
     }
   }
 
-  _onTranslateTabComplete(e: AnimationEvent) {
-    // If the end state is that the tab is not centered, then detach the content.
-    if (!this._isCenterPosition(e.toState) && !this._isCenterPosition(this._position)) {
-      this._portalOutlet.detach();
-    }
-
+  _onTranslateTabComplete(e: AnimationEvent): void {
     // If the transition to the center is complete, emit an event.
     if (this._isCenterPosition(e.toState) && this._isCenterPosition(this._position)) {
       this._onCentered.emit();
@@ -173,7 +204,7 @@ export class MatTabBody implements OnInit, AfterViewChecked {
   }
 
   /** Whether the provided position state is considered center, regardless of origin. */
-  private _isCenterPosition(position: MatTabBodyPositionState|string): boolean {
+  _isCenterPosition(position: MatTabBodyPositionState|string): boolean {
     return position == 'center' ||
         position == 'left-origin-center' ||
         position == 'right-origin-center';

src/lib/tabs/tab-group.spec.ts

@@ -26,15 +26,22 @@ describe('MatTabGroup', () => {
 
   describe('basic behavior', () => {
     let fixture: ComponentFixture<SimpleTabsTestApp>;
+    let element: HTMLElement;
 
     beforeEach(() => {
       fixture = TestBed.createComponent(SimpleTabsTestApp);
+      element = fixture.nativeElement;
     });
 
     it('should default to the first tab', () => {
       checkSelectedIndex(1, fixture);
     });
 
+    it('will properly load content on first change detection pass', () => {
+      fixture.detectChanges();
+      expect(element.querySelectorAll('.mat-tab-body')[1].querySelectorAll('span').length).toBe(3);
+    });
+
     it('should change selected index on click', () => {
       let component = fixture.debugElement.componentInstance;
       component.selectedIndex = 0;
@@ -318,23 +325,26 @@ describe('MatTabGroup', () => {
           fixture.debugElement.query(By.directive(MatTabGroup)).componentInstance as MatTabGroup;
     });
 
-    it('should support a tab-group with the simple api', () => {
+    it('should support a tab-group with the simple api', async(() => {
       expect(getSelectedLabel(fixture).textContent).toMatch('Junk food');
       expect(getSelectedContent(fixture).textContent).toMatch('Pizza, fries');
 
       tabGroup.selectedIndex = 2;
       fixture.detectChanges();
+      // Use whenStable to wait for async observables and change detection to run in content.
+      fixture.whenStable().then(() => {
 
-      expect(getSelectedLabel(fixture).textContent).toMatch('Fruit');
-      expect(getSelectedContent(fixture).textContent).toMatch('Apples, grapes');
+        expect(getSelectedLabel(fixture).textContent).toMatch('Fruit');
+        expect(getSelectedContent(fixture).textContent).toMatch('Apples, grapes');
 
-      fixture.componentInstance.otherLabel = 'Chips';
-      fixture.componentInstance.otherContent = 'Salt, vinegar';
-      fixture.detectChanges();
+        fixture.componentInstance.otherLabel = 'Chips';
+        fixture.componentInstance.otherContent = 'Salt, vinegar';
+        fixture.detectChanges();
 
-      expect(getSelectedLabel(fixture).textContent).toMatch('Chips');
-      expect(getSelectedContent(fixture).textContent).toMatch('Salt, vinegar');
-    });
+        expect(getSelectedLabel(fixture).textContent).toMatch('Chips');
+        expect(getSelectedContent(fixture).textContent).toMatch('Salt, vinegar');
+      });
+    }));
 
     it('should support @ViewChild in the tab content', () => {
       expect(fixture.componentInstance.legumes).toBeTruthy();
@@ -415,7 +425,7 @@ describe('nested MatTabGroup with enabled animations', () => {
       </mat-tab>
       <mat-tab>
         <ng-template mat-tab-label>Tab Two</ng-template>
-        Tab two content
+        <span>Tab </span><span>two</span><span>content</span>
       </mat-tab>
       <mat-tab>
         <ng-template mat-tab-label>Tab Three</ng-template>

src/lib/tabs/tabs-module.ts

@@ -14,7 +14,7 @@ import {NgModule} from '@angular/core';
 import {MatCommonModule, MatRippleModule} from '@angular/material/core';
 import {MatInkBar} from './ink-bar';
 import {MatTab} from './tab';
-import {MatTabBody} from './tab-body';
+import {MatTabBody, MatTabBodyPortal} from './tab-body';
 import {MatTabGroup} from './tab-group';
 import {MatTabHeader} from './tab-header';
 import {MatTabLabel} from './tab-label';
@@ -49,6 +49,7 @@ import {MatTabLink, MatTabNav} from './tab-nav-bar/tab-nav-bar';
     MatTabNav,
     MatTabLink,
     MatTabBody,
+    MatTabBodyPortal,
     MatTabHeader
   ],
   providers: [VIEWPORT_RULER_PROVIDER],