fix(selection-list): tabIndex should respect disabled state

* Currently if the selection-list is disabled, the tabIndex may be still set to a valid value that allows tabbing to the element. The `mixinTabIndex` respects the disabled state of the selection list.

src/lib/list/selection-list.spec.ts

@@ -214,6 +214,49 @@ describe('MdSelectionList', () => {
     });
   });
 
+  describe('with tabindex', () => {
+
+    beforeEach(async(() => {
+      TestBed.configureTestingModule({
+        imports: [MdListModule],
+        declarations: [
+          SelectionListWithTabindexAttr,
+          SelectionListWithTabindexBinding,
+        ]
+      });
+
+      TestBed.compileComponents();
+    }));
+
+    it('should properly handle native tabindex attribute', () => {
+      const fixture = TestBed.createComponent(SelectionListWithTabindexAttr);
+      const selectionList = fixture.debugElement.query(By.directive(MdSelectionList));
+
+      expect(selectionList.componentInstance.tabIndex)
+        .toBe(5, 'Expected the selection-list tabindex to be set to the attribute value.');
+    });
+
+    it('should support changing the tabIndex through binding', () => {
+      const fixture = TestBed.createComponent(SelectionListWithTabindexBinding);
+      const selectionList = fixture.debugElement.query(By.directive(MdSelectionList));
+
+      expect(selectionList.componentInstance.tabIndex)
+        .toBe(0, 'Expected the tabIndex to be set to "0" by default.');
+
+      fixture.componentInstance.tabIndex = 3;
+      fixture.detectChanges();
+
+      expect(selectionList.componentInstance.tabIndex)
+        .toBe(3, 'Expected the tabIndex to updated through binding.');
+
+      fixture.componentInstance.disabled = true;
+      fixture.detectChanges();
+
+      expect(selectionList.componentInstance.tabIndex)
+        .toBe(-1, 'Expected the tabIndex to be set to "-1" if selection list is disabled.');
+    });
+  });
+
   describe('with single option', () => {
     let fixture: ComponentFixture<SelectionListWithOnlyOneOption>;
     let listOption: DebugElement;
@@ -458,3 +501,16 @@ class SelectionListWithDisabledOption {
   </mat-selection-list>`})
 class SelectionListWithOnlyOneOption {
 }
+
+@Component({
+  template: `<mat-selection-list tabindex="5"></mat-selection-list>`
+})
+class SelectionListWithTabindexAttr {}
+
+@Component({
+  template: `<mat-selection-list [tabIndex]="tabIndex" [disabled]="disabled"></mat-selection-list>`
+})
+class SelectionListWithTabindexBinding {
+  tabIndex: number;
+  disabled: boolean;
+}

src/lib/list/selection-list.ts

@@ -23,6 +23,7 @@ import {
   OnDestroy,
   forwardRef,
   Inject,
+  Attribute,
 } from '@angular/core';
 import {coerceBooleanProperty, SelectionModel, MdLine, MdLineSetter} from '../core';
 import {FocusKeyManager} from '../core/a11y/focus-key-manager';
@@ -34,11 +35,13 @@ import {RxChain, switchMap, startWith} from '../core/rxjs/index';
 import {merge} from 'rxjs/observable/merge';
 import {CanDisableRipple, mixinDisableRipple} from '../core/common-behaviors/disable-ripple';
 import {MATERIAL_COMPATIBILITY_MODE} from '../core/compatibility/compatibility';
+import {mixinTabIndex, HasTabIndex} from '../core/common-behaviors/tabindex';
 
 
 /** @docs-private */
 export class MdSelectionListBase {}
-export const _MdSelectionListMixinBase = mixinDisableRipple(mixinDisabled(MdSelectionListBase));
+export const _MdSelectionListMixinBase =
+  mixinTabIndex(mixinDisableRipple(mixinDisabled(MdSelectionListBase)));
 
 /** @docs-private */
 export class MdListOptionBase {}
@@ -182,10 +185,10 @@ export class MdListOption extends _MdListOptionMixinBase
 @Component({
   moduleId: module.id,
   selector: 'md-selection-list, mat-selection-list',
-  inputs: ['disabled', 'disableRipple'],
+  inputs: ['disabled', 'disableRipple', 'tabIndex'],
   host: {
     'role': 'listbox',
-    '[attr.tabindex]': '_tabIndex',
+    '[tabIndex]': 'tabIndex',
     'class': 'mat-selection-list',
     '(focus)': 'focus()',
     '(keydown)': '_keydown($event)',
@@ -195,11 +198,8 @@ export class MdListOption extends _MdListOptionMixinBase
   encapsulation: ViewEncapsulation.None,
   changeDetection: ChangeDetectionStrategy.OnPush
 })
-export class MdSelectionList extends _MdSelectionListMixinBase
-    implements FocusableOption, CanDisable, CanDisableRipple, AfterContentInit, OnDestroy {
-
-  /** Tab index for the selection-list. */
-  _tabIndex = 0;
+export class MdSelectionList extends _MdSelectionListMixinBase implements FocusableOption,
+    CanDisable, CanDisableRipple, HasTabIndex, AfterContentInit, OnDestroy {
 
   /** Subscription to all list options' onFocus events */
   private _optionFocusSubscription = Subscription.EMPTY;
@@ -216,17 +216,15 @@ export class MdSelectionList extends _MdSelectionListMixinBase
   /** The currently selected options. */
   selectedOptions: SelectionModel<MdListOption> = new SelectionModel<MdListOption>(true);
 
-  constructor(private _element: ElementRef) {
+  constructor(private _element: ElementRef, @Attribute('tabindex') tabIndex: string) {
     super();
+
+    this.tabIndex = parseInt(tabIndex) || 0;
   }
 
   ngAfterContentInit(): void {
     this._keyManager = new FocusKeyManager<MdListOption>(this.options).withWrap();
 
-    if (this.disabled) {
-      this._tabIndex = -1;
-    }
-
     this._optionFocusSubscription = this._onFocusSubscription();
     this._optionDestroyStream = this._onDestroySubscription();
   }