feat(router): guard returning UrlTree cancels current navigation and redirects (#26521)

Fixes #24618
FW-153 #resolve

PR Close #26521

aio/content/guide/router.md

@@ -3066,11 +3066,13 @@ A guard's return value controls the router's behavior:
 
 * If it returns `true`, the navigation process continues.
 * If it returns `false`, the navigation process stops and the user stays put.
+* If it returns a `UrlTree`, the current navigation cancels and a new navigation is initiated to the `UrlTree` returned.
 
 
 <div class="alert is-helpful">
 
-**Note:** The guard can also tell the router to navigate elsewhere, effectively canceling the current navigation.
+**Note:** The guard can also tell the router to navigate elsewhere, effectively canceling the current navigation. When
+doing so inside a guard, the guard should return `false`;
 
 </div>
 

packages/router/src/interfaces.ts

@@ -17,6 +17,10 @@ import {UrlSegment, UrlTree} from './url_tree';
  * @description
  *
  * Interface that a class can implement to be a guard deciding if a route can be activated.
+ * If all guards return `true`, navigation will continue. If any guard returns `false`,
+ * navigation will be cancelled. If any guard returns a `UrlTree`, current navigation will
+ * be cancelled and a new navigation will be kicked off to the `UrlTree` returned from the
+ * guard.
  *
  * ```
  * class UserToken {}
@@ -33,7 +37,7 @@ import {UrlSegment, UrlTree} from './url_tree';
  *   canActivate(
  *     route: ActivatedRouteSnapshot,
  *     state: RouterStateSnapshot
- *   ): Observable<boolean>|Promise<boolean>|boolean|UrlTree {
+ *   ): Observable<boolean|UrlTree>|Promise<boolean|UrlTree>|boolean|UrlTree {
  *     return this.permissions.canActivate(this.currentUser, route.params.id);
  *   }
  * }
@@ -90,7 +94,11 @@ export type CanActivateFn = (route: ActivatedRouteSnapshot, state: RouterStateSn
  * @description
  *
  * Interface that a class can implement to be a guard deciding if a child route can be activated.
- *
+ * If all guards return `true`, navigation will continue. If any guard returns `false`,
+ * navigation will be cancelled. If any guard returns a `UrlTree`, current navigation will
+ * be cancelled and a new navigation will be kicked off to the `UrlTree` returned from the
+ * guard.
+ * 
  * ```
  * class UserToken {}
  * class Permissions {
@@ -106,7 +114,7 @@ export type CanActivateFn = (route: ActivatedRouteSnapshot, state: RouterStateSn
  *   canActivateChild(
  *     route: ActivatedRouteSnapshot,
  *     state: RouterStateSnapshot
- *   ): Observable<boolean>|Promise<boolean>|boolean|UrlTree {
+ *   ): Observable<boolean|UrlTree>|Promise<boolean|UrlTree>|boolean|UrlTree {
  *     return this.permissions.canActivate(this.currentUser, route.params.id);
  *   }
  * }
@@ -173,7 +181,11 @@ export type CanActivateChildFn = (childRoute: ActivatedRouteSnapshot, state: Rou
  * @description
  *
  * Interface that a class can implement to be a guard deciding if a route can be deactivated.
- *
+ * If all guards return `true`, navigation will continue. If any guard returns `false`,
+ * navigation will be cancelled. If any guard returns a `UrlTree`, current navigation will
+ * be cancelled and a new navigation will be kicked off to the `UrlTree` returned from the
+ * guard.
+ * 
  * ```
  * class UserToken {}
  * class Permissions {
@@ -191,7 +203,7 @@ export type CanActivateChildFn = (childRoute: ActivatedRouteSnapshot, state: Rou
  *     currentRoute: ActivatedRouteSnapshot,
  *     currentState: RouterStateSnapshot,
  *     nextState: RouterStateSnapshot
- *   ): Observable<boolean>|Promise<boolean>|boolean|UrlTree {
+ *   ): Observable<boolean|UrlTree>|Promise<boolean|UrlTree>|boolean|UrlTree {
  *     return this.permissions.canDeactivate(this.currentUser, route.params.id);
  *   }
  * }

packages/router/src/operators/check_guards.ts

@@ -17,7 +17,7 @@ import {ActivatedRouteSnapshot, RouterStateSnapshot} from '../router_state';
 import {UrlTree} from '../url_tree';
 import {wrapIntoObservable} from '../utils/collection';
 import {CanActivate, CanDeactivate, getCanActivateChild, getToken} from '../utils/preactivation';
-import {isCanActivate, isCanActivateChild, isCanDeactivate, isFunction, isBoolean} from '../utils/type_guards';
+import {isBoolean, isCanActivate, isCanActivateChild, isCanDeactivate, isFunction} from '../utils/type_guards';
 
 import {prioritizedGuardValue} from './prioritized_guard_value';
 

packages/router/src/operators/prioritized_guard_value.ts

@@ -7,9 +7,10 @@
  */
 
 import {Observable, OperatorFunction, combineLatest} from 'rxjs';
-import {filter, scan, startWith, switchMap, take} from 'rxjs/operators';
+import {filter, map, scan, startWith, switchMap, take} from 'rxjs/operators';
 
 import {UrlTree} from '../url_tree';
+import {isUrlTree} from '../utils/type_guards';
 
 const INITIAL_VALUE = Symbol('INITIAL_VALUE');
 declare type INTERIM_VALUES = typeof INITIAL_VALUE | boolean | UrlTree;
@@ -38,7 +39,7 @@ export function prioritizedGuardValue():
                       // navigation
                       if (val === false) return val;
 
-                      if (i === list.length - 1 || val instanceof UrlTree) {
+                      if (i === list.length - 1 || isUrlTree(val)) {
                         return val;
                       }
                     }
@@ -47,6 +48,8 @@ export function prioritizedGuardValue():
                   }, acc);
                 },
                 INITIAL_VALUE),
-            filter(item => item !== INITIAL_VALUE), take(1)) as Observable<boolean|UrlTree>;
+            filter(item => item !== INITIAL_VALUE),
+            map(item => isUrlTree(item) ? item : item === true),  //
+            take(1)) as Observable<boolean|UrlTree>;
   });
 }

packages/router/src/router.ts

@@ -8,7 +8,7 @@
 
 import {Location} from '@angular/common';
 import {Compiler, Injector, NgModuleFactoryLoader, NgModuleRef, NgZone, Type, isDevMode, ɵConsole as Console} from '@angular/core';
-import {BehaviorSubject, EMPTY, Observable, Subject, Subscription, of } from 'rxjs';
+import {BehaviorSubject, EMPTY, Observable, Subject, Subscription, defer, of } from 'rxjs';
 import {catchError, filter, finalize, map, switchMap, tap} from 'rxjs/operators';
 
 import {QueryParamsHandling, Route, Routes, standardizeConfig, validateConfig} from './config';
@@ -25,10 +25,11 @@ import {DefaultRouteReuseStrategy, RouteReuseStrategy} from './route_reuse_strat
 import {RouterConfigLoader} from './router_config_loader';
 import {ChildrenOutletContexts} from './router_outlet_context';
 import {ActivatedRoute, RouterState, RouterStateSnapshot, createEmptyState} from './router_state';
-import {Params, isNavigationCancelingError} from './shared';
+import {Params, isNavigationCancelingError, navigationCancelingError} from './shared';
 import {DefaultUrlHandlingStrategy, UrlHandlingStrategy} from './url_handling_strategy';
 import {UrlSerializer, UrlTree, containsTree, createEmptyUrlTree} from './url_tree';
 import {Checks, getAllRouteGuards} from './utils/preactivation';
+import {isUrlTree} from './utils/type_guards';
 
 
 
@@ -487,6 +488,14 @@ export class Router {
                   })),
 
               checkGuards(this.ngModule.injector, (evt: Event) => this.triggerEvent(evt)),
+              tap(t => {
+                if (isUrlTree(t.guardsResult)) {
+                  const error: Error&{url?: UrlTree} = navigationCancelingError(
+                      `Redirecting to "${this.serializeUrl(t.guardsResult)}"`);
+                  error.url = t.guardsResult;
+                  throw error;
+                }
+              }),
 
               tap(t => {
                 const guardsEnd = new GuardsCheckEnd(
@@ -602,11 +611,19 @@ export class Router {
                  * rather than an error. */
                 if (isNavigationCancelingError(e)) {
                   this.navigated = true;
-                  this.resetStateAndUrl(t.currentRouterState, t.currentUrlTree, t.rawUrl);
+                  const redirecting = isUrlTree(e.url);
+                  if (!redirecting) {
+                    this.resetStateAndUrl(t.currentRouterState, t.currentUrlTree, t.rawUrl);
+                  }
                   const navCancel =
                       new NavigationCancel(t.id, this.serializeUrl(t.extractedUrl), e.message);
                   eventsSubject.next(navCancel);
                   t.resolve(false);
+
+                  if (redirecting) {
+                    this.navigateByUrl(e.url);
+                  }
+
                   /* All other errors should reset to the router's internal URL reference to the
                    * pre-error state. */
                 } else {
@@ -815,7 +832,7 @@ export class Router {
           `Navigation triggered outside Angular zone, did you forget to call 'ngZone.run()'?`);
     }
 
-    const urlTree = url instanceof UrlTree ? url : this.parseUrl(url);
+    const urlTree = isUrlTree(url) ? url : this.parseUrl(url);
     const mergedTree = this.urlHandlingStrategy.merge(urlTree, this.rawUrlTree);
 
     return this.scheduleNavigation(mergedTree, 'imperative', null, extras);
@@ -867,7 +884,7 @@ export class Router {
 
   /** Returns whether the url is activated */
   isActive(url: string|UrlTree, exact: boolean): boolean {
-    if (url instanceof UrlTree) {
+    if (isUrlTree(url)) {
       return containsTree(this.currentUrlTree, url, exact);
     }
 

packages/router/src/utils/type_guards.ts

@@ -7,6 +7,7 @@
  */
 
 import {CanActivate, CanActivateChild, CanDeactivate, CanLoad} from '../interfaces';
+import {UrlTree} from '../url_tree';
 
 /**
  * Simple function check, but generic so type inference will flow. Example:
@@ -29,6 +30,10 @@ export function isBoolean(v: any): v is boolean {
   return typeof v === 'boolean';
 }
 
+export function isUrlTree(v: any): v is UrlTree {
+  return v instanceof UrlTree;
+}
+
 export function isCanLoad(guard: any): guard is CanLoad {
   return guard && isFunction<CanLoad>(guard.canLoad);
 }
@@ -38,7 +43,7 @@ export function isCanActivate(guard: any): guard is CanActivate {
 }
 
 export function isCanActivateChild(guard: any): guard is CanActivateChild {
-  return guard && isFunction<CanActivateChild>(guard.canActivate);
+  return guard && isFunction<CanActivateChild>(guard.canActivateChild);
 }
 
 export function isCanDeactivate<T>(guard: any): guard is CanDeactivate<T> {

packages/router/test/integration.spec.ts

@@ -9,7 +9,7 @@
 import {CommonModule, Location} from '@angular/common';
 import {SpyLocation} from '@angular/common/testing';
 import {ChangeDetectionStrategy, Component, Injectable, NgModule, NgModuleFactoryLoader, NgModuleRef, NgZone, OnDestroy, ɵConsole as Console, ɵNoopNgZone as NoopNgZone} from '@angular/core';
-import {ComponentFixture, TestBed, fakeAsync, inject, tick} from '@angular/core/testing';
+import {ComponentFixture, TestBed, fakeAsync, flush, inject, tick} from '@angular/core/testing';
 import {By} from '@angular/platform-browser/src/dom/debug/by';
 import {expect} from '@angular/platform-browser/testing/src/matchers';
 import {ActivatedRoute, ActivatedRouteSnapshot, ActivationEnd, ActivationStart, CanActivate, CanDeactivate, ChildActivationEnd, ChildActivationStart, DetachedRouteHandle, Event, GuardsCheckEnd, GuardsCheckStart, NavigationCancel, NavigationEnd, NavigationError, NavigationStart, PRIMARY_OUTLET, ParamMap, Params, PreloadAllModules, PreloadingStrategy, Resolve, ResolveEnd, ResolveStart, RouteConfigLoadEnd, RouteConfigLoadStart, RouteReuseStrategy, Router, RouterEvent, RouterModule, RouterPreloader, RouterStateSnapshot, RoutesRecognized, RunGuardsAndResolvers, UrlHandlingStrategy, UrlSegmentGroup, UrlSerializer, UrlTree} from '@angular/router';
@@ -2017,6 +2017,59 @@ describe('Integration', () => {
            })));
       });
 
+      describe('should redirect when guard returns UrlTree', () => {
+        beforeEach(() => TestBed.configureTestingModule({
+          providers: [{
+            provide: 'returnUrlTree',
+            useFactory: (router: Router) => () => { return router.parseUrl('/redirected'); },
+            deps: [Router]
+          }]
+        }));
+
+        it('works', 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: ['returnUrlTree']},
+               {path: 'redirected', component: SimpleCmp}
+             ]);
+
+             const fixture = TestBed.createComponent(RootCmp);
+             router.navigateByUrl('/one');
+
+             advance(fixture);
+
+             expect(location.path()).toEqual('/redirected');
+             expect(fixture.nativeElement).toHaveText('simple');
+             expect(cancelEvent && cancelEvent.reason)
+                 .toBe('NavigationCancelingError: Redirecting to "/redirected"');
+             expectEvents(recordedEvents, [
+               [NavigationStart, '/one'],
+               [RoutesRecognized, '/one'],
+               [GuardsCheckStart, '/one'],
+               [ChildActivationStart, undefined],
+               [ActivationStart, undefined],
+               [NavigationCancel, '/one'],
+               [NavigationStart, '/redirected'],
+               [RoutesRecognized, '/redirected'],
+               [GuardsCheckStart, '/redirected'],
+               [ChildActivationStart, undefined],
+               [ActivationStart, undefined],
+               [GuardsCheckEnd, '/redirected'],
+               [ResolveStart, '/redirected'],
+               [ResolveEnd, '/redirected'],
+               [ActivationEnd, undefined],
+               [ChildActivationEnd, undefined],
+               [NavigationEnd, '/redirected'],
+             ]);
+           })));
+      });
+
       describe('runGuardsAndResolvers', () => {
         let guardRunCount = 0;
         let resolverRunCount = 0;

packages/router/test/router.spec.ts

@@ -672,10 +672,11 @@ function checkGuards(
     guards: getAllRouteGuards(future, curr, new ChildrenOutletContexts())
   } as Partial<NavigationTransition>)
       .pipe(checkGuardsOperator(injector))
-      .subscribe(
+      .subscribe({
-          t => {
+        next(t) {
-            if (t.guardsResult === null) throw new Error('Guard result expected');
+          if (t.guardsResult === null) throw new Error('Guard result expected');
-            return check(t.guardsResult);
+          return check(t.guardsResult);
-          },
+        },
-          (e) => { throw e; });
+        error(e) { throw e; }
+      });
 }