feat(material/tabs): Refactor MatTabNav to follow the ARIA tabs patte…

…rn (#24062)

by introducing a new tabpanel component.

src/components-examples/material/tabs/index.ts

@@ -20,6 +20,7 @@ import {TabGroupLazyLoadedExample} from './tab-group-lazy-loaded/tab-group-lazy-
 import {TabGroupStretchedExample} from './tab-group-stretched/tab-group-stretched-example';
 import {TabGroupThemeExample} from './tab-group-theme/tab-group-theme-example';
 import {TabNavBarBasicExample} from './tab-nav-bar-basic/tab-nav-bar-basic-example';
+import {TabNavBarWithPanelExample} from './tab-nav-bar-with-panel/tab-nav-bar-with-panel-example';
 
 export {
   TabGroupAlignExample,
@@ -35,6 +36,7 @@ export {
   TabGroupStretchedExample,
   TabGroupThemeExample,
   TabNavBarBasicExample,
+  TabNavBarWithPanelExample,
 };
 
 const EXAMPLES = [
@@ -51,6 +53,7 @@ const EXAMPLES = [
   TabGroupStretchedExample,
   TabGroupThemeExample,
   TabNavBarBasicExample,
+  TabNavBarWithPanelExample,
 ];
 
 @NgModule({

src/components-examples/material/tabs/tab-nav-bar-with-panel/tab-nav-bar-with-panel-example.css

@@ -0,0 +1,4 @@
+.example-action-button {
+  margin-top: 8px;
+  margin-right: 8px;
+}

src/components-examples/material/tabs/tab-nav-bar-with-panel/tab-nav-bar-with-panel-example.html

@@ -0,0 +1,9 @@
+<!-- #docregion mat-tab-nav -->
+<nav mat-tab-nav-bar [tabPanel]="tabPanel">
+  <a mat-tab-link *ngFor="let link of links"
+     (click)="activeLink = link"
+     [active]="activeLink == link"> {{link}} </a>
+  <a mat-tab-link disabled>Disabled Link</a>
+</nav>
+<mat-tab-nav-panel #tabPanel></mat-tab-nav-panel>
+<!-- #enddocregion mat-tab-nav -->

src/components-examples/material/tabs/tab-nav-bar-with-panel/tab-nav-bar-with-panel-example.ts

@@ -0,0 +1,14 @@
+import {Component} from '@angular/core';
+
+/**
+ * @title Use of the tab nav bar with the dedicated panel component.
+ */
+@Component({
+  selector: 'tab-nav-bar-with-panel-example',
+  templateUrl: 'tab-nav-bar-with-panel-example.html',
+  styleUrls: ['tab-nav-bar-with-panel-example.css'],
+})
+export class TabNavBarWithPanelExample {
+  links = ['First', 'Second', 'Third'];
+  activeLink = this.links[0];
+}

src/dev-app/mdc-tabs/mdc-tabs-demo.html

@@ -127,4 +127,13 @@ <h2>Tab nav bar</h2>
       [active]="activeLink == link">{{link}}</a>
     <a mat-tab-link disabled>Disabled Link</a>
   </nav>
+
+  <h2>Tab nav bar with panel</h2>
+  <nav mat-tab-nav-bar [tabPanel]="tabPanel">
+    <a mat-tab-link *ngFor="let link of links"
+      (click)="activeLink = link"
+      [active]="activeLink == link">{{link}}</a>
+    <a mat-tab-link disabled>Disabled Link</a>
+  </nav>
+  <mat-tab-nav-panel #tabPanel></mat-tab-nav-panel>
 </div>

src/dev-app/tabs/tabs-demo.html

@@ -18,5 +18,7 @@ <h3>Tab group stretched</h3>
 <tab-group-stretched-example></tab-group-stretched-example>
 <h3>Tab group theming</h3>
 <tab-group-theme-example></tab-group-theme-example>
-<h3>Tab Navigation Bar basic</h3>
+<h3>Tab navigation bar basic</h3>
 <tab-nav-bar-basic-example></tab-nav-bar-basic-example>
+<h3>Tab navigation bar with panel</h3>
+<tab-nav-bar-with-panel-example></tab-nav-bar-with-panel-example>

src/material-experimental/mdc-tabs/module.ts

@@ -19,7 +19,7 @@ import {MatTabLabelWrapper} from './tab-label-wrapper';
 import {MatTab} from './tab';
 import {MatTabHeader} from './tab-header';
 import {MatTabGroup} from './tab-group';
-import {MatTabNav, MatTabLink} from './tab-nav-bar/tab-nav-bar';
+import {MatTabNav, MatTabNavPanel, MatTabLink} from './tab-nav-bar/tab-nav-bar';
 
 @NgModule({
   imports: [
@@ -37,6 +37,7 @@ import {MatTabNav, MatTabLink} from './tab-nav-bar/tab-nav-bar';
     MatTab,
     MatTabGroup,
     MatTabNav,
+    MatTabNavPanel,
     MatTabLink,
   ],
   declarations: [
@@ -45,6 +46,7 @@ import {MatTabNav, MatTabLink} from './tab-nav-bar/tab-nav-bar';
     MatTab,
     MatTabGroup,
     MatTabNav,
+    MatTabNavPanel,
     MatTabLink,
 
     // Private directives, should not be exported.

src/material-experimental/mdc-tabs/public-api.ts

@@ -15,7 +15,7 @@ export {MatTab} from './tab';
 export {MatInkBar} from './ink-bar';
 export {MatTabHeader} from './tab-header';
 export {MatTabGroup} from './tab-group';
-export {MatTabNav, MatTabLink} from './tab-nav-bar/tab-nav-bar';
+export {MatTabNav, MatTabNavPanel, MatTabLink} from './tab-nav-bar/tab-nav-bar';
 
 export {
   MatTabBodyPositionState,

src/material-experimental/mdc-tabs/tab-nav-bar/tab-nav-bar.spec.ts

@@ -1,11 +1,16 @@
+import {SPACE} from '@angular/cdk/keycodes';
 import {waitForAsync, ComponentFixture, fakeAsync, TestBed, tick} from '@angular/core/testing';
 import {Component, QueryList, ViewChild, ViewChildren} from '@angular/core';
 import {
   MAT_RIPPLE_GLOBAL_OPTIONS,
   RippleGlobalOptions,
 } from '@angular/material-experimental/mdc-core';
 import {By} from '@angular/platform-browser';
-import {dispatchFakeEvent, dispatchMouseEvent} from '../../../cdk/testing/private';
+import {
+  dispatchFakeEvent,
+  dispatchKeyboardEvent,
+  dispatchMouseEvent,
+} from '../../../cdk/testing/private';
 import {Direction, Directionality} from '@angular/cdk/bidi';
 import {Subject} from 'rxjs';
 import {MatTabsModule} from '../module';
@@ -30,6 +35,7 @@ describe('MDC-based MatTabNavBar', () => {
           TabLinkWithTabIndexBinding,
           TabLinkWithNativeTabindexAttr,
           TabBarWithInactiveTabsOnInit,
+          TabBarWithPanel,
         ],
         providers: [
           {provide: MAT_RIPPLE_GLOBAL_OPTIONS, useFactory: () => globalRippleOptions},
@@ -309,6 +315,123 @@ describe('MDC-based MatTabNavBar', () => {
     expect(instance.tabNavBar.selectedIndex).toBe(1);
   });
 
+  describe('without panel', () => {
+    let fixture: ComponentFixture<SimpleTabNavBarTestApp>;
+
+    beforeEach(() => {
+      fixture = TestBed.createComponent(SimpleTabNavBarTestApp);
+      fixture.detectChanges();
+    });
+
+    it('should have no explicit roles', () => {
+      const tabBar = fixture.nativeElement.querySelector('.mat-mdc-tab-nav-bar')!;
+      expect(tabBar.getAttribute('role')).toBe(null);
+
+      const tabLinks = fixture.nativeElement.querySelectorAll('.mat-mdc-tab-link');
+      expect(tabLinks[0].getAttribute('role')).toBe(null);
+      expect(tabLinks[1].getAttribute('role')).toBe(null);
+      expect(tabLinks[2].getAttribute('role')).toBe(null);
+    });
+
+    it('should not setup aria-controls', () => {
+      const tabLinks = fixture.nativeElement.querySelectorAll('.mat-mdc-tab-link');
+      expect(tabLinks[0].getAttribute('aria-controls')).toBe(null);
+      expect(tabLinks[1].getAttribute('aria-controls')).toBe(null);
+      expect(tabLinks[2].getAttribute('aria-controls')).toBe(null);
+    });
+
+    it('should not manage aria-selected', () => {
+      const tabLinks = fixture.nativeElement.querySelectorAll('.mat-mdc-tab-link');
+      expect(tabLinks[0].getAttribute('aria-selected')).toBe(null);
+      expect(tabLinks[1].getAttribute('aria-selected')).toBe(null);
+      expect(tabLinks[2].getAttribute('aria-selected')).toBe(null);
+    });
+
+    it('should not activate a link when space is pressed', () => {
+      const tabLinks = fixture.nativeElement.querySelectorAll('.mat-mdc-tab-link');
+      expect(tabLinks[1].classList.contains('mdc-tab--active')).toBe(false);
+
+      dispatchKeyboardEvent(tabLinks[1], 'keydown', SPACE);
+      fixture.detectChanges();
+
+      expect(tabLinks[1].classList.contains('mdc-tab--active')).toBe(false);
+    });
+  });
+
+  describe('with panel', () => {
+    let fixture: ComponentFixture<TabBarWithPanel>;
+
+    beforeEach(() => {
+      fixture = TestBed.createComponent(TabBarWithPanel);
+      fixture.detectChanges();
+    });
+
+    it('should have the proper roles', () => {
+      const tabBar = fixture.nativeElement.querySelector('.mat-mdc-tab-nav-bar')!;
+      expect(tabBar.getAttribute('role')).toBe('tablist');
+
+      const tabLinks = fixture.nativeElement.querySelectorAll('.mat-mdc-tab-link');
+      expect(tabLinks[0].getAttribute('role')).toBe('tab');
+      expect(tabLinks[1].getAttribute('role')).toBe('tab');
+      expect(tabLinks[2].getAttribute('role')).toBe('tab');
+
+      const tabPanel = fixture.nativeElement.querySelector('.mat-mdc-tab-nav-panel')!;
+      expect(tabPanel.getAttribute('role')).toBe('tabpanel');
+    });
+
+    it('should manage tabindex properly', () => {
+      const tabLinks = fixture.nativeElement.querySelectorAll('.mat-mdc-tab-link');
+      expect(tabLinks[0].tabIndex).toBe(0);
+      expect(tabLinks[1].tabIndex).toBe(-1);
+      expect(tabLinks[2].tabIndex).toBe(-1);
+
+      tabLinks[1].click();
+      fixture.detectChanges();
+
+      expect(tabLinks[0].tabIndex).toBe(-1);
+      expect(tabLinks[1].tabIndex).toBe(0);
+      expect(tabLinks[2].tabIndex).toBe(-1);
+    });
+
+    it('should setup aria-controls properly', () => {
+      const tabLinks = fixture.nativeElement.querySelectorAll('.mat-mdc-tab-link');
+      expect(tabLinks[0].getAttribute('aria-controls')).toBe('tab-panel');
+      expect(tabLinks[1].getAttribute('aria-controls')).toBe('tab-panel');
+      expect(tabLinks[2].getAttribute('aria-controls')).toBe('tab-panel');
+    });
+
+    it('should not manage aria-current', () => {
+      const tabLinks = fixture.nativeElement.querySelectorAll('.mat-mdc-tab-link');
+      expect(tabLinks[0].getAttribute('aria-current')).toBe(null);
+      expect(tabLinks[1].getAttribute('aria-current')).toBe(null);
+      expect(tabLinks[2].getAttribute('aria-current')).toBe(null);
+    });
+
+    it('should manage aria-selected properly', () => {
+      const tabLinks = fixture.nativeElement.querySelectorAll('.mat-mdc-tab-link');
+      expect(tabLinks[0].getAttribute('aria-selected')).toBe('true');
+      expect(tabLinks[1].getAttribute('aria-selected')).toBe('false');
+      expect(tabLinks[2].getAttribute('aria-selected')).toBe('false');
+
+      tabLinks[1].click();
+      fixture.detectChanges();
+
+      expect(tabLinks[0].getAttribute('aria-selected')).toBe('false');
+      expect(tabLinks[1].getAttribute('aria-selected')).toBe('true');
+      expect(tabLinks[2].getAttribute('aria-selected')).toBe('false');
+    });
+
+    it('should activate a link when space is pressed', () => {
+      const tabLinks = fixture.nativeElement.querySelectorAll('.mat-mdc-tab-link');
+      expect(tabLinks[1].classList.contains('mdc-tab--active')).toBe(false);
+
+      dispatchKeyboardEvent(tabLinks[1], 'keydown', SPACE);
+      fixture.detectChanges();
+
+      expect(tabLinks[1].classList.contains('mdc-tab--active')).toBe(true);
+    });
+  });
+
   describe('ripples', () => {
     let fixture: ComponentFixture<SimpleTabNavBarTestApp>;
 
@@ -532,3 +655,21 @@ class TabLinkWithNativeTabindexAttr {}
 class TabBarWithInactiveTabsOnInit {
   tabs = [0, 1, 2];
 }
+
+@Component({
+  template: `
+    <nav mat-tab-nav-bar [tabPanel]="tabPanel">
+      <a mat-tab-link
+         *ngFor="let tab of tabs; let index = index"
+         [active]="index === activeIndex"
+         (click)="activeIndex = index">
+         Tab link
+      </a>
+    </nav>
+    <mat-tab-nav-panel #tabPanel id="tab-panel">Tab panel</mat-tab-nav-panel>
+  `,
+})
+class TabBarWithPanel {
+  tabs = [0, 1, 2];
+  activeIndex = 0;
+}

src/material-experimental/mdc-tabs/tab-nav-bar/tab-nav-bar.ts

@@ -56,6 +56,7 @@ import {takeUntil} from 'rxjs/operators';
   templateUrl: 'tab-nav-bar.html',
   styleUrls: ['tab-nav-bar.css'],
   host: {
+    '[attr.role]': '_getRole()',
     'class': 'mat-mdc-tab-nav-bar mat-mdc-tab-header',
     '[class.mat-mdc-tab-header-pagination-controls-enabled]': '_showPaginationControls',
     '[class.mat-mdc-tab-header-rtl]': "_getLayoutDirection() == 'rtl'",
@@ -127,12 +128,17 @@ export class MatTabNav extends _MatTabNavBase implements AfterContentInit {
   styleUrls: ['tab-link.css'],
   host: {
     'class': 'mdc-tab mat-mdc-tab-link mat-mdc-focus-indicator',
-    '[attr.aria-current]': 'active ? "page" : null',
+    '[attr.aria-controls]': '_getAriaControls()',
+    '[attr.aria-current]': '_getAriaCurrent()',
     '[attr.aria-disabled]': 'disabled',
-    '[attr.tabIndex]': 'tabIndex',
+    '[attr.aria-selected]': '_getAriaSelected()',
+    '[attr.id]': 'id',
+    '[attr.tabIndex]': '_getTabIndex()',
+    '[attr.role]': '_getRole()',
     '[class.mat-mdc-tab-disabled]': 'disabled',
     '[class.mdc-tab--active]': 'active',
     '(focus)': '_handleFocus()',
+    '(keydown)': '_handleKeydown($event)',
   },
 })
 export class MatTabLink extends _MatTabLinkBase implements MatInkBarItem, OnInit, OnDestroy {
@@ -167,3 +173,30 @@ export class MatTabLink extends _MatTabLinkBase implements MatInkBarItem, OnInit
     this._foundation.destroy();
   }
 }
+
+// Increasing integer for generating unique ids for tab nav components.
+let nextUniqueId = 0;
+
+/**
+ * Tab panel component associated with MatTabNav.
+ */
+@Component({
+  selector: 'mat-tab-nav-panel',
+  exportAs: 'matTabNavPanel',
+  template: '<ng-content></ng-content>',
+  host: {
+    '[attr.aria-labelledby]': '_activeTabId',
+    '[attr.id]': 'id',
+    'class': 'mat-mdc-tab-nav-panel',
+    'role': 'tabpanel',
+  },
+  encapsulation: ViewEncapsulation.None,
+  changeDetection: ChangeDetectionStrategy.OnPush,
+})
+export class MatTabNavPanel {
+  /** Unique id for the tab panel. */
+  @Input() id = `mat-tab-nav-panel-${nextUniqueId++}`;
+
+  /** Id of the active tab in the nav bar. */
+  _activeTabId?: string;
+}

src/material-experimental/mdc-tabs/testing/tab-harness-filters.ts

@@ -27,3 +27,6 @@ export interface TabLinkHarnessFilters extends BaseHarnessFilters {
 
 /** A set of criteria that can be used to filter a list of `MatTabNavBarHarness` instances. */
 export interface TabNavBarHarnessFilters extends BaseHarnessFilters {}
+
+/** A set of criteria that can be used to filter a list of `MatTabNavBarHarness` instances. */
+export interface TabNavPanelHarnessFilters extends BaseHarnessFilters {}

src/material-experimental/mdc-tabs/testing/tab-nav-bar-harness.ts

@@ -7,8 +7,13 @@
  */
 
 import {ComponentHarness, HarnessPredicate, parallel} from '@angular/cdk/testing';
-import {TabNavBarHarnessFilters, TabLinkHarnessFilters} from './tab-harness-filters';
+import {
+  TabNavBarHarnessFilters,
+  TabNavPanelHarnessFilters,
+  TabLinkHarnessFilters,
+} from './tab-harness-filters';
 import {MatTabLinkHarness} from './tab-link-harness';
+import {MatTabNavPanelHarness} from './tab-nav-panel-harness';
 
 /** Harness for interacting with an MDC-based mat-tab-nav-bar in tests. */
 export class MatTabNavBarHarness extends ComponentHarness {
@@ -57,4 +62,17 @@ export class MatTabNavBarHarness extends ComponentHarness {
     }
     await tabs[0].click();
   }
+
+  /** Gets the panel associated with the nav bar. */
+  async getPanel(): Promise<MatTabNavPanelHarness> {
+    const link = await this.getActiveLink();
+    const host = await link.host();
+    const panelId = await host.getAttribute('aria-controls');
+    if (!panelId) {
+      throw Error('No panel is controlled by the nav bar.');
+    }
+
+    const filter: TabNavPanelHarnessFilters = {selector: `#${panelId}`};
+    return await this.documentRootLocatorFactory().locatorFor(MatTabNavPanelHarness.with(filter))();
+  }
 }