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.

Author: devversion

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

@@ -256,6 +256,49 @@ describe('MatSelectionList', () => {
     });
   });
 
+  describe('with tabindex', () => {
+
+    beforeEach(async(() => {
+      TestBed.configureTestingModule({
+        imports: [MatListModule],
+        declarations: [
+          SelectionListWithTabindexAttr,
+          SelectionListWithTabindexBinding,
+        ]
+      });
+
+      TestBed.compileComponents();
+    }));
+
+    it('should properly handle native tabindex attribute', () => {
+      const fixture = TestBed.createComponent(SelectionListWithTabindexAttr);
+      const selectionList = fixture.debugElement.query(By.directive(MatSelectionList));
+
+      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(MatSelectionList));
+
+      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;
@@ -509,3 +552,16 @@ class SelectionListWithSelectedOption {
   </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

@@ -12,6 +12,7 @@ import {SelectionModel} from '@angular/cdk/collections';
 import {SPACE} from '@angular/cdk/keycodes';
 import {
   AfterContentInit,
+  Attribute,
   ChangeDetectionStrategy,
   ChangeDetectorRef,
   Component,
@@ -32,16 +33,19 @@ import {
 import {
   CanDisable,
   CanDisableRipple,
+  HasTabIndex,
   MatLine,
   MatLineSetter,
   mixinDisabled,
   mixinDisableRipple,
+  mixinTabIndex,
 } from '@angular/material/core';
 
 
 /** @docs-private */
 export class MatSelectionListBase {}
-export const _MatSelectionListMixinBase = mixinDisableRipple(mixinDisabled(MatSelectionListBase));
+export const _MatSelectionListMixinBase =
+  mixinTabIndex(mixinDisableRipple(mixinDisabled(MatSelectionListBase)));
 
 /** @docs-private */
 export class MatListOptionBase {}
@@ -178,10 +182,10 @@ export class MatListOption extends _MatListOptionMixinBase
 @Component({
   moduleId: module.id,
   selector: '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)',
@@ -192,11 +196,8 @@ export class MatListOption extends _MatListOptionMixinBase
   preserveWhitespaces: false,
   changeDetection: ChangeDetectionStrategy.OnPush
 })
-export class MatSelectionList extends _MatSelectionListMixinBase
-    implements FocusableOption, CanDisable, CanDisableRipple, AfterContentInit {
-
-  /** Tab index for the selection-list. */
-  _tabIndex = 0;
+export class MatSelectionList extends _MatSelectionListMixinBase implements FocusableOption,
+    CanDisable, CanDisableRipple, HasTabIndex, AfterContentInit {
 
   /** The FocusKeyManager which handles focus. */
   _keyManager: FocusKeyManager<MatListOption>;
@@ -207,16 +208,14 @@ export class MatSelectionList extends _MatSelectionListMixinBase
   /** The currently selected options. */
   selectedOptions: SelectionModel<MatListOption> = new SelectionModel<MatListOption>(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<MatListOption>(this.options).withWrap();
-
-    if (this.disabled) {
-      this._tabIndex = -1;
-    }
   }
 
   /** Focus the selection-list. */