fix(router): fix navigation ignoring logic to compare to the browser url

This PR changes the logic for determining when to skip route processing from
using the URL of the last attempted navigation to the actual resulting URL after
that transition.

Because guards may prevent navigation and reset the browser URL, the raw
URL of the previous transition may not match the actual URL of the
browser at the end of the navigation process. For that reason, we need to use
`urlAfterRedirects` instead.

Other notes:
These checks in scheduleNavigation were added in angular@eb2ceff
The test still passes and, more surprisingly, passes if the checks are removed
completely. There have likely been changes to the navigation handling that
handle the test in a different way. That said, it still appears to be important
to keep the checks there in some capacity because it does affect how many
navigation events occur. This addresses an issue that came up in angular#16710: angular#16710 (comment)
This also partially addresses angular#13586 in fixing history for imperative
navigations that are cancelled by guards.

packages/router/src/router.ts

@@ -1126,12 +1126,31 @@ export class Router {
       rawUrl: UrlTree, source: NavigationTrigger, restoredState: RestoredState|null,
       extras: NavigationExtras,
       priorPromise?: {resolve: any, reject: any, promise: Promise<boolean>}): Promise<boolean> {
+    // * Imperative navigations (router.navigate) might trigger additional navigations to the same
+    //   URL via a popstate event and the locationChangeListener. We should skip these duplicate
+    //   navs. Duplicates may also be triggered by attempts to sync AngularJS and Angular router
+    //   states.
+    // * Imperative navigations can be cancelled by router guards, meaning the URL won't change. If
+    //   the user follows that with a navigation using the back/forward button or manual URL change,
+    //   the destination may be the same as the previous imperative attempt. We should not skip
+    //   these navigations because it's a separate case from the one above -- it's not a duplicate
+    //   navigation.
     const lastNavigation = this.getTransition();
-    // If the user triggers a navigation imperatively (e.g., by using navigateByUrl),
-    // and that navigation results in 'replaceState' that leads to the same URL,
-    // we should skip those.
-    if (lastNavigation && source !== 'imperative' && lastNavigation.source === 'imperative' &&
-        lastNavigation.rawUrl.toString() === rawUrl.toString()) {
+    // The rawUrl is where the navigation is trying to go at the start. The final url
+    // may be different based on guards and redirects.
+    const navAttemptSameAsPrevious = lastNavigation.rawUrl.toString() === rawUrl.toString();
+    const navIsSameAsInFlightNav = this.currentNavigation && navAttemptSameAsPrevious;
+    // We don't want to skip duplicate successful navs if they're imperative because
+    // onSameUrlNavigation could be 'reload' (so the duplicate is intended).
+    const browserNavPrecededByRouterNav =
+        source !== 'imperative' && lastNavigation?.source === 'imperative';
+    const lastNavigationSucceeded = this.lastSuccessfulId === lastNavigation.id;
+    // If the last navigation succeeded, we can use the rawUrl as the comparison.
+    // However, if it failed, we should compare to the final result (urlAfterRedirects).
+    const duplicateNav = lastNavigationSucceeded ?
+        navAttemptSameAsPrevious :
+        lastNavigation.urlAfterRedirects.toString() === rawUrl.toString();
+    if (browserNavPrecededByRouterNav && (duplicateNav || navIsSameAsInFlightNav)) {
       return Promise.resolve(true);  // return value is not used
     }
 

packages/router/test/integration.spec.ts

@@ -909,7 +909,7 @@ describe('Integration', () => {
        expect(cmp.recordedUrls()).toEqual(['one/two', 'three/four']);
      })));
 
-  describe('should reset location if a navigation by location is successful', () => {
+  describe('duplicate in-flight navigations', () => {
     beforeEach(() => {
       TestBed.configureTestingModule({
         providers: [{
@@ -924,7 +924,27 @@ describe('Integration', () => {
       });
     });
 
-    it('work', fakeAsync(inject([Router, Location], (router: Router, location: Location) => {
+    it('should ignore the duplicate resulting from a location sync', fakeAsync(() => {
+         const router = TestBed.inject(Router);
+         const fixture = createRoot(router, RootCmp);
+         const location = TestBed.inject(Location) as SpyLocation;
+         router.resetConfig([{path: 'simple', component: SimpleCmp, canActivate: ['in1Second']}]);
+
+         const recordedEvents: any[] = [];
+         router.events.forEach(e => onlyNavigationStartAndEnd(e) && recordedEvents.push(e));
+
+         setTimeout(() => {
+           router.navigateByUrl('/simple');
+         }, 0);
+         location.simulateUrlPop('/simple');
+         tick(1000);
+         advance(fixture);
+         expectEvents(recordedEvents, [[NavigationStart, '/simple'], [NavigationEnd, '/simple']]);
+       }));
+
+    it('should reset location if a navigation by location is successful', fakeAsync(() => {
+         const router = TestBed.inject(Router);
+         const location = TestBed.inject(Location) as SpyLocation;
          const fixture = createRoot(router, RootCmp);
 
          router.resetConfig([{path: 'simple', component: SimpleCmp, canActivate: ['in1Second']}]);
@@ -936,14 +956,14 @@ describe('Integration', () => {
          // - location change 'simple'
          // - the first location change gets canceled, the URL gets reset to '/'
          // - the second location change gets finished, the URL should be reset to '/simple'
-         (<any>location).simulateUrlPop('/simple');
-         (<any>location).simulateUrlPop('/simple');
+         location.simulateUrlPop('/simple');
+         location.simulateUrlPop('/simple');
 
          tick(2000);
          advance(fixture);
 
          expect(location.path()).toEqual('/simple');
-       })));
+       }));
   });
 
   it('should support secondary routes', fakeAsync(inject([Router], (router: Router) => {
@@ -2539,6 +2559,161 @@ describe('Integration', () => {
            })));
       });
 
+      describe('should not break the history', () => {
+        @Injectable({providedIn: 'root'})
+        class MyGuard implements CanDeactivate<any> {
+          allow: boolean = true;
+          canDeactivate(): boolean {
+            return this.allow;
+          }
+        }
+
+        @Component({selector: 'parent', template: '<router-outlet></router-outlet>'})
+        class Parent {
+        }
+
+        @Component({selector: 'home', template: 'home'})
+        class Home {
+        }
+
+        @Component({selector: 'child1', template: 'child1'})
+        class Child1 {
+        }
+
+        @Component({selector: 'child2', template: 'child2'})
+        class Child2 {
+        }
+
+        @Component({selector: 'child3', template: 'child3'})
+        class Child3 {
+        }
+
+        @Component({selector: 'child4', template: 'child4'})
+        class Child4 {
+        }
+
+        @Component({selector: 'child5', template: 'child5'})
+        class Child5 {
+        }
+
+        @NgModule({
+          declarations: [Parent, Home, Child1, Child2, Child3, Child4, Child5],
+          entryComponents: [Child1, Child2, Child3, Child4, Child5],
+          imports: [RouterModule]
+        })
+        class TestModule {
+        }
+
+        let fixture: ComponentFixture<unknown>;
+
+        beforeEach(fakeAsync(() => {
+          TestBed.configureTestingModule({imports: [TestModule]});
+          const router = TestBed.get(Router);
+          const location = TestBed.get(Location);
+          fixture = createRoot(router, Parent);
+
+          router.resetConfig([
+            {path: '', component: Home},
+            {path: 'first', component: Child1},
+            {path: 'second', component: Child2},
+            {path: 'third', component: Child3, canDeactivate: [MyGuard]},
+            {path: 'fourth', component: Child4},
+            {path: 'fifth', component: Child5},
+          ]);
+
+          // Create a navigation history of pages 1-5, and go back to 3 so that there is both
+          // back and forward history.
+          router.navigateByUrl('/first');
+          advance(fixture);
+          router.navigateByUrl('/second');
+          advance(fixture);
+          router.navigateByUrl('/third');
+          advance(fixture);
+          router.navigateByUrl('/fourth');
+          advance(fixture);
+          router.navigateByUrl('/fifth');
+          advance(fixture);
+          location.back();
+          advance(fixture);
+          location.back();
+          advance(fixture);
+        }));
+
+        // TODO(https://github.com/angular/angular/issues/13586)
+        // A fix to this requires much more design
+        xit('when navigate back using Back button', fakeAsync(() => {
+              const location = TestBed.get(Location);
+              expect(location.path()).toEqual('/third');
+
+              TestBed.get(MyGuard).allow = false;
+              location.back();
+              advance(fixture);
+              expect(location.path()).toEqual('/third');
+              expect(fixture.nativeElement).toHaveText('child3');
+
+              TestBed.get(MyGuard).allow = true;
+              location.back();
+              advance(fixture);
+              expect(location.path()).toEqual('/second');
+              expect(fixture.nativeElement).toHaveText('child2');
+            }));
+
+        it('when navigate back imperatively', fakeAsync(() => {
+             const router = TestBed.get(Router);
+             const location = TestBed.get(Location);
+             expect(location.path()).toEqual('/third');
+
+             TestBed.get(MyGuard).allow = false;
+             router.navigateByUrl('/second');
+             advance(fixture);
+             expect(location.path()).toEqual('/third');
+             expect(fixture.nativeElement).toHaveText('child3');
+
+             TestBed.get(MyGuard).allow = true;
+             location.back();
+             advance(fixture);
+             expect(location.path()).toEqual('/second');
+             expect(fixture.nativeElement).toHaveText('child2');
+           }));
+
+        // TODO(https://github.com/angular/angular/issues/13586)
+        // A fix to this requires much more design
+        xit('when navigate back using Foward button', fakeAsync(() => {
+              const location = TestBed.get(Location);
+              expect(location.path()).toEqual('/third');
+
+              TestBed.get(MyGuard).allow = false;
+              location.forward();
+              advance(fixture);
+              expect(location.path()).toEqual('/third');
+              expect(fixture.nativeElement).toHaveText('child3');
+
+              TestBed.get(MyGuard).allow = true;
+              location.forward();
+              advance(fixture);
+              expect(location.path()).toEqual('/fourth');
+              expect(fixture.nativeElement).toHaveText('child4');
+            }));
+
+        it('when navigate forward imperatively', fakeAsync(() => {
+             const router = TestBed.get(Router);
+             const location = TestBed.get(Location);
+             expect(location.path()).toEqual('/third');
+
+             TestBed.get(MyGuard).allow = false;
+             router.navigateByUrl('/fourth');
+             advance(fixture);
+             expect(location.path()).toEqual('/third');
+             expect(fixture.nativeElement).toHaveText('child3');
+
+             TestBed.get(MyGuard).allow = true;
+             location.forward();
+             advance(fixture);
+             expect(location.path()).toEqual('/fourth');
+             expect(fixture.nativeElement).toHaveText('child4');
+           }));
+      });
+
       describe('should redirect when guard returns UrlTree', () => {
         beforeEach(() => TestBed.configureTestingModule({
           providers: [