fix(sidenav): don't restore focus if focus isn't inside sidenav (#4578)

* fix(sidenav): don't restore focus if focus isn't inside sidenav

* inject document

src/lib/sidenav/sidenav.spec.ts

@@ -1,5 +1,5 @@
 import {fakeAsync, async, tick, ComponentFixture, TestBed} from '@angular/core/testing';
-import {Component, ViewChild} from '@angular/core';
+import {Component, ElementRef, ViewChild} from '@angular/core';
 import {By} from '@angular/platform-browser';
 import {MdSidenav, MdSidenavModule, MdSidenavToggleResult, MdSidenavContainer} from './index';
 import {A11yModule} from '../core/a11y/index';
@@ -310,19 +310,20 @@ describe('MdSidenav', () => {
       expect(testComponent.closeCount).toBe(0);
     }));
 
-    it('should restore focus to the trigger element on close', fakeAsync(() => {
+    it('should restore focus on close if focus is inside sidenav', fakeAsync(() => {
       let fixture = TestBed.createComponent(BasicTestApp);
       let sidenav: MdSidenav = fixture.debugElement
         .query(By.directive(MdSidenav)).componentInstance;
-      let trigger = document.createElement('button');
+      let openButton = fixture.componentInstance.openButton.nativeElement;
+      let sidenavButton = fixture.componentInstance.sidenavButton.nativeElement;
 
-      document.body.appendChild(trigger);
-      trigger.focus();
+      openButton.focus();
       sidenav.open();
 
       fixture.detectChanges();
       endSidenavTransition(fixture);
       tick();
+      sidenavButton.focus();
 
       sidenav.close();
 
@@ -331,9 +332,32 @@ describe('MdSidenav', () => {
       tick();
 
       expect(document.activeElement)
-          .toBe(trigger, 'Expected focus to be restored to the trigger on close.');
+          .toBe(openButton, 'Expected focus to be restored to the open button on close.');
+    }));
+
+    it('should not restore focus on close if focus is outside sidenav', fakeAsync(() => {
+      let fixture = TestBed.createComponent(BasicTestApp);
+      let sidenav: MdSidenav = fixture.debugElement
+          .query(By.directive(MdSidenav)).componentInstance;
+      let openButton = fixture.componentInstance.openButton.nativeElement;
+      let closeButton = fixture.componentInstance.closeButton.nativeElement;
+
+      openButton.focus();
+      sidenav.open();
+
+      fixture.detectChanges();
+      endSidenavTransition(fixture);
+      tick();
+      closeButton.focus();
+
+      sidenav.close();
 
-      trigger.parentNode.removeChild(trigger);
+      fixture.detectChanges();
+      endSidenavTransition(fixture);
+      tick();
+
+      expect(document.activeElement)
+          .toBe(closeButton, 'Expected focus not to be restored to the open button on close.');
     }));
   });
 
@@ -508,10 +532,10 @@ class SidenavContainerTwoSidenavTestApp {
                   (open)="open()"
                   (close-start)="closeStart()"
                   (close)="close()">
-        Content.
+        <button #sidenavButton>Content.</button>
       </md-sidenav>
-      <button (click)="sidenav.open()" class="open"></button>
-      <button (click)="sidenav.close()" class="close"></button>
+      <button (click)="sidenav.open()" class="open" #openButton></button>
+      <button (click)="sidenav.close()" class="close" #closeButton></button>
     </md-sidenav-container>`,
 })
 class BasicTestApp {
@@ -521,6 +545,10 @@ class BasicTestApp {
   closeCount: number = 0;
   backdropClickedCount: number = 0;
 
+  @ViewChild('sidenavButton') sidenavButton: ElementRef;
+  @ViewChild('openButton') openButton: ElementRef;
+  @ViewChild('closeButton') closeButton: ElementRef;
+
   openStart() {
     this.openStartCount++;
   }

src/lib/sidenav/sidenav.ts

@@ -12,12 +12,13 @@ import {
   Renderer2,
   ViewEncapsulation,
   NgZone,
-  OnDestroy,
+  OnDestroy, Inject,
 } from '@angular/core';
 import {Dir, coerceBooleanProperty} from '../core';
 import {FocusTrapFactory, FocusTrap} from '../core/a11y/focus-trap';
 import {ESCAPE} from '../core/keyboard/keycodes';
 import 'rxjs/add/operator/first';
+import {DOCUMENT} from '@angular/platform-browser';
 
 
 /** Throws an exception when two MdSidenav are matching the same side. */
@@ -126,24 +127,37 @@ export class MdSidenav implements AfterContentInit, OnDestroy {
    * @param _elementRef The DOM element reference. Used for transition and width calculation.
    *     If not available we do not hook on transitions.
    */
-  constructor(private _elementRef: ElementRef, private _focusTrapFactory: FocusTrapFactory) {
+  constructor(private _elementRef: ElementRef,
+              private _focusTrapFactory: FocusTrapFactory,
+              @Optional() @Inject(DOCUMENT) private _doc: any) {
     this.onOpen.subscribe(() => {
-      this._elementFocusedBeforeSidenavWasOpened = document.activeElement as HTMLElement;
+      if (this._doc) {
+        this._elementFocusedBeforeSidenavWasOpened = this._doc.activeElement as HTMLElement;
+      }
 
       if (this.isFocusTrapEnabled && this._focusTrap) {
         this._focusTrap.focusInitialElementWhenReady();
       }
     });
 
-    this.onClose.subscribe(() => {
+    this.onClose.subscribe(() => this._restoreFocus());
+  }
+
+  /**
+   * If focus is currently inside the sidenav, restores it to where it was before the sidenav
+   * opened.
+   */
+  private _restoreFocus() {
+    let activeEl = this._doc && this._doc.activeElement;
+    if (activeEl && this._elementRef.nativeElement.contains(activeEl)) {
       if (this._elementFocusedBeforeSidenavWasOpened instanceof HTMLElement) {
         this._elementFocusedBeforeSidenavWasOpened.focus();
       } else {
         this._elementRef.nativeElement.blur();
       }
+    }
 
-      this._elementFocusedBeforeSidenavWasOpened = null;
-    });
+    this._elementFocusedBeforeSidenavWasOpened = null;
   }
 
   ngAfterContentInit() {