fix(router): error if module is destroyed before location is initialized (#42560)

This is something I ran into while working on a fix for the `TestBed` module teardown behavior for #18831. In the `RouterInitializer.appInitializer` we have a callback to the `LOCATION_INITIALIZED` which has to do some DI lookups. The problem is that if the module is destroyed before the location promise resolves, the `Injector.get` calls will fail. This is unlikely to happen in a real app, but it'll show up in unit tests once the test module teardown behavior is fixed.

PR Close #42560

packages/router/src/router_module.ts

@@ -7,7 +7,7 @@
  */
 
 import {APP_BASE_HREF, HashLocationStrategy, Location, LOCATION_INITIALIZED, LocationStrategy, PathLocationStrategy, PlatformLocation, ViewportScroller} from '@angular/common';
-import {ANALYZE_FOR_ENTRY_COMPONENTS, APP_BOOTSTRAP_LISTENER, APP_INITIALIZER, ApplicationRef, Compiler, ComponentRef, Inject, Injectable, InjectionToken, Injector, ModuleWithProviders, NgModule, NgModuleFactoryLoader, NgProbeToken, Optional, Provider, SkipSelf, SystemJsNgModuleLoader} from '@angular/core';
+import {ANALYZE_FOR_ENTRY_COMPONENTS, APP_BOOTSTRAP_LISTENER, APP_INITIALIZER, ApplicationRef, Compiler, ComponentRef, Inject, Injectable, InjectionToken, Injector, ModuleWithProviders, NgModule, NgModuleFactoryLoader, NgProbeToken, OnDestroy, Optional, Provider, SkipSelf, SystemJsNgModuleLoader} from '@angular/core';
 import {of, Subject} from 'rxjs';
 
 import {EmptyOutletComponent} from './components/empty_outlet';
@@ -503,8 +503,9 @@ export function rootRoute(router: Router): ActivatedRoute {
  * pauses. It waits for the hook to be resolved. We then resolve it only in a bootstrap listener.
  */
 @Injectable()
-export class RouterInitializer {
-  private initNavigation: boolean = false;
+export class RouterInitializer implements OnDestroy {
+  private initNavigation = false;
+  private destroyed = false;
   private resultOfPreactivationDone = new Subject<void>();
 
   constructor(private injector: Injector) {}
@@ -512,6 +513,11 @@ export class RouterInitializer {
   appInitializer(): Promise<any> {
     const p: Promise<any> = this.injector.get(LOCATION_INITIALIZED, Promise.resolve(null));
     return p.then(() => {
+      // If the injector was destroyed, the DI lookups below will fail.
+      if (this.destroyed) {
+        return Promise.resolve(true);
+      }
+
       let resolve: Function = null!;
       const res = new Promise(r => resolve = r);
       const router = this.injector.get(Router);
@@ -566,6 +572,10 @@ export class RouterInitializer {
     this.resultOfPreactivationDone.next(null!);
     this.resultOfPreactivationDone.complete();
   }
+
+  ngOnDestroy() {
+    this.destroyed = true;
+  }
 }
 
 export function getAppInitializer(r: RouterInitializer) {

packages/router/test/integration.spec.ts

@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {CommonModule, Location, LocationStrategy, PlatformLocation} from '@angular/common';
+import {APP_BASE_HREF, CommonModule, Location, LOCATION_INITIALIZED, LocationStrategy, PlatformLocation} from '@angular/common';
 import {SpyLocation} from '@angular/common/testing';
 import {ChangeDetectionStrategy, Component, EventEmitter, Injectable, NgModule, NgModuleFactoryLoader, NgModuleRef, NgZone, OnDestroy, ViewChild, ɵConsole as Console, ɵNoopNgZone as NoopNgZone} from '@angular/core';
 import {ComponentFixture, fakeAsync, inject, TestBed, tick} from '@angular/core/testing';
@@ -16,6 +16,7 @@ import {ActivatedRoute, ActivatedRouteSnapshot, ActivationEnd, ActivationStart,
 import {EMPTY, Observable, Observer, of, Subscription, SubscriptionLike} from 'rxjs';
 import {delay, filter, first, map, mapTo, tap} from 'rxjs/operators';
 
+import {RouterInitializer} from '../src/router_module';
 import {forEach} from '../src/utils/collection';
 import {RouterTestingModule, SpyNgModuleFactoryLoader} from '../testing';
 
@@ -6210,6 +6211,42 @@ describe('Integration', () => {
          expect(fixture).toContainComponent(Tool2Component, '(e)');
        }));
   });
+
+  describe('RouterInitializer', () => {
+    it('should not throw from appInitializer if module is destroyed before location is initialized',
+       done => {
+         let resolveInitializer: () => void;
+         let moduleRef: NgModuleRef<SelfDestructModule>;
+
+         @NgModule({
+           imports: [RouterModule.forRoot([])],
+           providers: [
+             {
+               provide: LOCATION_INITIALIZED,
+               useValue: new Promise<void>(resolve => resolveInitializer = resolve)
+             },
+             {
+               // Required when running the tests in a browser
+               provide: APP_BASE_HREF,
+               useValue: ''
+             }
+           ]
+         })
+         class SelfDestructModule {
+           constructor(ref: NgModuleRef<SelfDestructModule>, routerInitializer: RouterInitializer) {
+             moduleRef = ref;
+             routerInitializer.appInitializer().then(done, done.fail);
+           }
+         }
+
+         TestBed.resetTestingModule()
+             .configureTestingModule({imports: [SelfDestructModule], declarations: [SimpleCmp]})
+             .createComponent(SimpleCmp);
+
+         moduleRef!.destroy();
+         resolveInitializer!();
+       });
+  });
 });
 
 describe('Testing router options', () => {