fix(button-toggle): forward tabindex to underlying button (#12538)

src/lib/button-toggle/button-toggle.html

@@ -1,6 +1,7 @@
 <button #button class="mat-button-toggle-button"
         type="button"
         [id]="buttonId"
+        [attr.tabindex]="disabled ? -1 : tabIndex"
         [attr.aria-pressed]="checked"
         [disabled]="disabled || null"
         [attr.name]="name || null"

src/lib/button-toggle/button-toggle.spec.ts

@@ -211,6 +211,7 @@ describe('MatButtonToggle without forms', () => {
         ButtonToggleWithAriaLabel,
         ButtonToggleWithAriaLabelledby,
         RepeatedButtonTogglesWithPreselectedValue,
+        ButtonToggleWithTabindex,
       ],
     });
 
@@ -686,6 +687,26 @@ describe('MatButtonToggle without forms', () => {
     });
   });
 
+  describe('with tabindex ', () => {
+    it('should forward the tabindex to the underlying button', () => {
+      const fixture = TestBed.createComponent(ButtonToggleWithTabindex);
+      fixture.detectChanges();
+
+      const button = fixture.nativeElement.querySelector('.mat-button-toggle button');
+
+      expect(button.getAttribute('tabindex')).toBe('3');
+    });
+
+    it('should clear the tabindex from the host element', () => {
+      const fixture = TestBed.createComponent(ButtonToggleWithTabindex);
+      fixture.detectChanges();
+
+      const host = fixture.nativeElement.querySelector('.mat-button-toggle');
+
+      expect(host.hasAttribute('tabindex')).toBe(false);
+    });
+  });
+
   it('should not throw on init when toggles are repeated and there is an initial value', () => {
     const fixture = TestBed.createComponent(RepeatedButtonTogglesWithPreselectedValue);
 
@@ -855,3 +876,10 @@ class RepeatedButtonTogglesWithPreselectedValue {
   possibleValues = ['One', 'Two', 'Three'];
   value = 'Two';
 }
+
+
+@Component({
+  template: `<mat-button-toggle tabindex="3"></mat-button-toggle>`
+})
+class ButtonToggleWithTabindex {}
+

src/lib/button-toggle/button-toggle.ts

@@ -26,6 +26,7 @@ import {
   QueryList,
   ViewChild,
   ViewEncapsulation,
+  Attribute,
 } from '@angular/core';
 import {ControlValueAccessor, NG_VALUE_ACCESSOR} from '@angular/forms';
 import {
@@ -330,6 +331,8 @@ export const _MatButtonToggleMixinBase = mixinDisableRipple(MatButtonToggleBase)
     '[class.mat-button-toggle-checked]': 'checked',
     '[class.mat-button-toggle-disabled]': 'disabled',
     'class': 'mat-button-toggle',
+    // Clear out the native tabindex here since we forward it to the underlying button
+    '[attr.tabindex]': 'null',
     '[attr.id]': 'id',
   }
 })
@@ -370,6 +373,9 @@ export class MatButtonToggle extends _MatButtonToggleMixinBase implements OnInit
   /** MatButtonToggleGroup reads this to assign its own value. */
   @Input() value: any;
 
+  /** Tabindex for the toggle. */
+  @Input() tabIndex: number | null;
+
   /** Whether the button is checked. */
   @Input()
   get checked(): boolean {
@@ -404,9 +410,13 @@ export class MatButtonToggle extends _MatButtonToggleMixinBase implements OnInit
   constructor(@Optional() toggleGroup: MatButtonToggleGroup,
               private _changeDetectorRef: ChangeDetectorRef,
               private _elementRef: ElementRef<HTMLElement>,
-              private _focusMonitor: FocusMonitor) {
+              private _focusMonitor: FocusMonitor,
+              // @breaking-change 8.0.0 `defaultTabIndex` to be made a required parameter.
+              @Attribute('tabindex') defaultTabIndex: string) {
     super();
 
+    const parsedTabIndex = Number(defaultTabIndex);
+    this.tabIndex = (parsedTabIndex || parsedTabIndex === 0) ? parsedTabIndex : null;
     this.buttonToggleGroup = toggleGroup;
   }