fix(router): redirect to root url when returned as UrlTree from guard (#28271)

When a UrlTree of root url was returned by a guard as a redirection, the
navigation was not processed. The issue came from the error handler which
incorrectly marked the router as already navigated.

Fixes #27845

PR Close #28271

packages/router/src/router.ts

@@ -715,9 +715,14 @@ export class Router {
                 /* This error type is issued during Redirect, and is handled as a cancellation
                  * rather than an error. */
                 if (isNavigationCancelingError(e)) {
-                  this.navigated = true;
                   const redirecting = isUrlTree(e.url);
                   if (!redirecting) {
+                    // Set property only if we're not redirecting. If we landed on a page and
+                    // redirect to `/` route, the new navigation is going to see the `/` isn't
+                    // a change from the default currentUrlTree and won't navigate. This is
+                    // only applicable with initial navigation, so setting `navigated` only when
+                    // not redirecting resolves this scenario.
+                    this.navigated = true;
                     this.resetStateAndUrl(t.currentRouterState, t.currentUrlTree, t.rawUrl);
                   }
                   const navCancel =

packages/router/test/integration.spec.ts

@@ -2256,11 +2256,18 @@ describe('Integration', () => {
 
       describe('should redirect when guard returns UrlTree', () => {
         beforeEach(() => TestBed.configureTestingModule({
-          providers: [{
+          providers: [
-            provide: 'returnUrlTree',
+            {
-            useFactory: (router: Router) => () => { return router.parseUrl('/redirected'); },
+              provide: 'returnUrlTree',
-            deps: [Router]
+              useFactory: (router: Router) => () => { return router.parseUrl('/redirected'); },
-          }]
+              deps: [Router]
+            },
+            {
+              provide: 'returnRootUrlTree',
+              useFactory: (router: Router) => () => { return router.parseUrl('/'); },
+              deps: [Router]
+            }
+          ]
         }));
 
         it('works', fakeAsync(inject([Router, Location], (router: Router, location: Location) => {
@@ -2305,6 +2312,49 @@ describe('Integration', () => {
                [NavigationEnd, '/redirected'],
              ]);
            })));
+
+        it('works with root url',
+           fakeAsync(inject([Router, Location], (router: Router, location: Location) => {
+             const recordedEvents: any[] = [];
+             let cancelEvent: NavigationCancel = null !;
+             router.events.forEach((e: any) => {
+               recordedEvents.push(e);
+               if (e instanceof NavigationCancel) cancelEvent = e;
+             });
+             router.resetConfig([
+               {path: '', component: SimpleCmp},
+               {path: 'one', component: RouteCmp, canActivate: ['returnRootUrlTree']}
+             ]);
+
+             const fixture = TestBed.createComponent(RootCmp);
+             router.navigateByUrl('/one');
+
+             advance(fixture);
+
+             expect(location.path()).toEqual('/');
+             expect(fixture.nativeElement).toHaveText('simple');
+             expect(cancelEvent && cancelEvent.reason)
+                 .toBe('NavigationCancelingError: Redirecting to "/"');
+             expectEvents(recordedEvents, [
+               [NavigationStart, '/one'],
+               [RoutesRecognized, '/one'],
+               [GuardsCheckStart, '/one'],
+               [ChildActivationStart, undefined],
+               [ActivationStart, undefined],
+               [NavigationCancel, '/one'],
+               [NavigationStart, '/'],
+               [RoutesRecognized, '/'],
+               [GuardsCheckStart, '/'],
+               [ChildActivationStart, undefined],
+               [ActivationStart, undefined],
+               [GuardsCheckEnd, '/'],
+               [ResolveStart, '/'],
+               [ResolveEnd, '/'],
+               [ActivationEnd, undefined],
+               [ChildActivationEnd, undefined],
+               [NavigationEnd, '/'],
+             ]);
+           })));
       });
 
       describe('runGuardsAndResolvers', () => {