fix(material/tabs): prevent default keyboard actions on disabled links (#27274)

Fixes that while we were preventing clicks on disabled links using `pointer-events`, we didn't prevent keyboard events.

Fixes #27270.

(cherry picked from commit 2fbb81d)

Author: crisbeto

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

@@ -1,4 +1,4 @@
-import {SPACE} from '@angular/cdk/keycodes';
+import {ENTER, 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/core';
@@ -73,31 +73,6 @@ describe('MDC-based MatTabNavBar', () => {
       expect(tabLinkElements[1].classList.contains('mdc-tab--active')).toBeTruthy();
     });
 
-    it('should add the disabled class if disabled', () => {
-      const tabLinkElements = fixture.debugElement
-        .queryAll(By.css('a'))
-        .map(tabLinkDebugEl => tabLinkDebugEl.nativeElement);
-
-      expect(
-        tabLinkElements.every(tabLinkEl => {
-          return !tabLinkEl.classList.contains('mat-mdc-tab-disabled');
-        }),
-      )
-        .withContext('Expected every tab link to not have the disabled class initially')
-        .toBe(true);
-
-      fixture.componentInstance.disabled = true;
-      fixture.detectChanges();
-
-      expect(
-        tabLinkElements.every(tabLinkEl => {
-          return tabLinkEl.classList.contains('mat-mdc-tab-disabled');
-        }),
-      )
-        .withContext('Expected every tab link to have the disabled class if set through binding')
-        .toBe(true);
-    });
-
     it('should update aria-disabled if disabled', () => {
       const tabLinkElements = fixture.debugElement
         .queryAll(By.css('a'))
@@ -143,6 +118,20 @@ describe('MDC-based MatTabNavBar', () => {
       expect(tabLinkElement.classList).toContain('mat-mdc-tab-disabled');
     });
 
+    it('should prevent default keyboard actions on disabled links', () => {
+      const link = fixture.debugElement.query(By.css('a')).nativeElement;
+      fixture.componentInstance.disabled = true;
+      fixture.detectChanges();
+
+      const spaceEvent = dispatchKeyboardEvent(link, 'keydown', SPACE);
+      fixture.detectChanges();
+      expect(spaceEvent.defaultPrevented).toBe(true);
+
+      const enterEvent = dispatchKeyboardEvent(link, 'keydown', ENTER);
+      fixture.detectChanges();
+      expect(enterEvent.defaultPrevented).toBe(true);
+    });
+
     it('should re-align the ink bar when the direction changes', fakeAsync(() => {
       const inkBar = fixture.componentInstance.tabNavBar._inkBar;
 

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

@@ -48,7 +48,7 @@ import {MatInkBar, MatInkBarItem, mixinInkBarItem} from '../ink-bar';
 import {BooleanInput, coerceBooleanProperty, NumberInput} from '@angular/cdk/coercion';
 import {BehaviorSubject, Subject} from 'rxjs';
 import {startWith, takeUntil} from 'rxjs/operators';
-import {SPACE} from '@angular/cdk/keycodes';
+import {ENTER, SPACE} from '@angular/cdk/keycodes';
 import {MAT_TABS_CONFIG, MatTabsConfig} from '../tab-config';
 import {MatPaginatedTabHeader, MatPaginatedTabHeaderItem} from '../paginated-tab-header';
 
@@ -261,7 +261,9 @@ export class _MatTabLinkBase
   }
 
   _handleKeydown(event: KeyboardEvent) {
-    if (this._tabNavBar.tabPanel && event.keyCode === SPACE) {
+    if (this.disabled && (event.keyCode === SPACE || event.keyCode === ENTER)) {
+      event.preventDefault();
+    } else if (this._tabNavBar.tabPanel && event.keyCode === SPACE) {
       this.elementRef.nativeElement.click();
     }
   }