fix(router): make an outlet to unregister itself when it is removed from the dom

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

@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {Attribute, ComponentFactory, ComponentFactoryResolver, ComponentRef, Directive, EventEmitter, Injector, NoComponentFactoryError, Output, ReflectiveInjector, ResolvedReflectiveProvider, ViewContainerRef} from '@angular/core';
+import {Attribute, ComponentFactory, ComponentFactoryResolver, ComponentRef, Directive, EventEmitter, Injector, NoComponentFactoryError, OnDestroy, Output, ReflectiveInjector, ResolvedReflectiveProvider, ViewContainerRef} from '@angular/core';
 
 import {RouterOutletMap} from '../router_outlet_map';
 import {ActivatedRoute} from '../router_state';
@@ -38,7 +38,7 @@ import {PRIMARY_OUTLET} from '../shared';
  * @stable
  */
 @Directive({selector: 'router-outlet'})
-export class RouterOutlet {
+export class RouterOutlet implements OnDestroy {
   private activated: ComponentRef<any>;
   private _activatedRoute: ActivatedRoute;
   public outletMap: RouterOutletMap;
@@ -47,11 +47,13 @@ export class RouterOutlet {
   @Output('deactivate') deactivateEvents = new EventEmitter<any>();
 
   constructor(
-      parentOutletMap: RouterOutletMap, private location: ViewContainerRef,
-      private resolver: ComponentFactoryResolver, @Attribute('name') name: string) {
+      private parentOutletMap: RouterOutletMap, private location: ViewContainerRef,
+      private resolver: ComponentFactoryResolver, @Attribute('name') private name: string) {
     parentOutletMap.registerOutlet(name ? name : PRIMARY_OUTLET, this);
   }
 
+  ngOnDestroy(): void { this.parentOutletMap.removeOutlet(this.name ? this.name : PRIMARY_OUTLET); }
+
   get isActivated(): boolean { return !!this.activated; }
   get component(): Object {
     if (!this.activated) throw new Error('Outlet is not activated');

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

@@ -15,4 +15,6 @@ export class RouterOutletMap {
   /** @internal */
   _outlets: {[name: string]: RouterOutlet} = {};
   registerOutlet(name: string, outlet: RouterOutlet): void { this._outlets[name] = outlet; }
+
+  removeOutlet(name: string): void { this._outlets[name] = undefined; }
 }

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

@@ -63,6 +63,38 @@ describe('Integration', () => {
            expect(location.path()).toEqual('/child/simple');
          })));
 
+  it('should work when an outlet is in an ngIf (and is removed)',
+     fakeAsync(inject(
+         [Router, TestComponentBuilder, Location],
+         (router: Router, tcb: TestComponentBuilder, location: Location) => {
+           @Component({
+             selector: 'someRoot',
+             template: `<div *ngIf="cond"><router-outlet></router-outlet></div>`,
+             entryComponents: [BlankCmp, SimpleCmp]
+           })
+           class RootCmpWithLink {
+             cond: boolean = true;
+           }
+
+           const fixture = createRoot(tcb, router, RootCmpWithLink);
+
+           router.resetConfig(
+               [{path: 'simple', component: SimpleCmp}, {path: 'blank', component: BlankCmp}]);
+
+           router.navigateByUrl('/simple');
+           advance(fixture);
+           expect(location.path()).toEqual('/simple');
+
+           const instance = fixture.componentInstance;
+           instance.cond = false;
+           advance(fixture);
+
+           let recordedError: any = null;
+           router.navigateByUrl('/blank').catch(e => recordedError = e);
+           advance(fixture);
+           expect(recordedError.message).toEqual('Cannot find primary outlet to load \'BlankCmp\'');
+         })));
+
   it('should update location when navigating',
      fakeAsync(inject(
          [Router, TestComponentBuilder, Location],

tools/public_api_guard/router/index.d.ts

@@ -228,7 +228,7 @@ export declare class RouterModule {
 }
 
 /** @stable */
-export declare class RouterOutlet {
+export declare class RouterOutlet implements OnDestroy {
     activateEvents: EventEmitter<any>;
     activatedRoute: ActivatedRoute;
     component: Object;
@@ -238,11 +238,13 @@ export declare class RouterOutlet {
     constructor(parentOutletMap: RouterOutletMap, location: ViewContainerRef, resolver: ComponentFactoryResolver, name: string);
     activate(activatedRoute: ActivatedRoute, loadedResolver: ComponentFactoryResolver, loadedInjector: Injector, providers: ResolvedReflectiveProvider[], outletMap: RouterOutletMap): void;
     deactivate(): void;
+    ngOnDestroy(): void;
 }
 
 /** @stable */
 export declare class RouterOutletMap {
     registerOutlet(name: string, outlet: RouterOutlet): void;
+    removeOutlet(name: string): void;
 }
 
 /** @stable */