fix(router): do not fire events on 'duplicate' location events

modules/@angular/router/src/router.ts

@@ -288,7 +288,14 @@ export class Router {
 
   private setUpLocationChangeListener(): void {
     this.locationSubscription = <any>this.location.subscribe((change) => {
-      return this.scheduleNavigation(this.urlSerializer.parse(change['url']), change['pop']);
+      const tree = this.urlSerializer.parse(change['url']);
+      // we fire multiple events for a single URL change
+      // we should navigate only once
+      if (this.currentUrlTree.toString() !== tree.toString()) {
+        return this.scheduleNavigation(tree, change['pop']);
+      } else {
+        return null;
+      }
     });
   }
 

modules/@angular/router/test/router.spec.ts

@@ -111,13 +111,27 @@ describe('Integration', () => {
              children: [{path: 'user/:name', component: UserCmp}]
            }]);
 
+           const recordedEvents: any = [];
+           router.events.forEach(e => recordedEvents.push(e));
+
            router.navigateByUrl('/team/22/user/victor');
            advance(fixture);
 
            (<any>location).simulateHashChange('/team/22/user/fedor');
            advance(fixture);
 
-           expect(fixture.debugElement.nativeElement).toHaveText('team 22 [ user fedor, right:  ]');
+           (<any>location).simulateUrlPop('/team/22/user/fedor');
+           advance(fixture);
+
+           expect(fixture.debugElement.nativeElement).toHaveText('team 22 { user fedor, right:  }');
+
+           expectEvents(recordedEvents, [
+             [NavigationStart, '/team/22/user/victor'], [RoutesRecognized, '/team/22/user/victor'],
+             [NavigationEnd, '/team/22/user/victor'],
+
+             [NavigationStart, '/team/22/user/fedor'], [RoutesRecognized, '/team/22/user/fedor'],
+             [NavigationEnd, '/team/22/user/fedor']
+           ]);
          })));
 
   it('should update the location when the matched route does not change',