fix(router): lazy loading keeps refetching modules (#10707)

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

@@ -244,10 +244,14 @@ class ApplyRedirects {
     } else if (route.loadChildren) {
       return runGuards(injector, route).mergeMap(shouldLoad => {
         if (shouldLoad) {
-          return this.configLoader.load(injector, route.loadChildren).map(r => {
-            (<any>route)._loadedConfig = r;
-            return r;
-          });
+          if ((<any>route)._loadedConfig) {
+            return of ((<any>route)._loadedConfig);
+          } else {
+            return this.configLoader.load(injector, route.loadChildren).map(r => {
+              (<any>route)._loadedConfig = r;
+              return r;
+            });
+          }
         } else {
           return canLoadFails(route);
         }

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

@@ -406,7 +406,6 @@ export class Router {
           })
           .forEach((shouldActivate: boolean) => {
             if (!shouldActivate || id !== this.navigationId) {
-              this.routerEvents.next(new NavigationCancel(id, this.serializeUrl(url)));
               navigationIsSuccessful = false;
               return;
             }
@@ -429,9 +428,14 @@ export class Router {
           .then(
               () => {
                 this.navigated = true;
-                this.routerEvents.next(
-                    new NavigationEnd(id, this.serializeUrl(url), this.serializeUrl(appliedUrl)));
-                resolvePromise(navigationIsSuccessful);
+                if (navigationIsSuccessful) {
+                  this.routerEvents.next(
+                      new NavigationEnd(id, this.serializeUrl(url), this.serializeUrl(appliedUrl)));
+                  resolvePromise(true);
+                } else {
+                  this.routerEvents.next(new NavigationCancel(id, this.serializeUrl(url)));
+                  resolvePromise(false);
+                }
               },
               e => {
                 this.currentRouterState = storedState;

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

@@ -266,6 +266,32 @@ describe('applyRedirects', () => {
         expect((<any>config[1])._loadedConfig).toBe(loadedConfig);
       });
     });
+
+    it('should load the configuration only once', () => {
+      const loadedConfig = new LoadedRouterConfig(
+          [{path: '', component: ComponentB}], <any>'stubInjector', <any>'stubFactoryResolver');
+
+      let called = false;
+      const loader = {
+        load: (injector: any, p: any) => {
+          if (called) throw new Error('Should not be called twice');
+          called = true;
+          return of (loadedConfig);
+        }
+      };
+
+      const config = [{path: 'a', loadChildren: 'children'}];
+
+      applyRedirects(<any>'providedInjector', <any>loader, tree('a?k1'), config).subscribe(r => {});
+
+      applyRedirects(<any>'providedInjector', <any>loader, tree('a?k2'), config)
+          .subscribe(
+              r => {
+                compareTrees(r, tree('a'));
+                expect((<any>config[0])._loadedConfig).toBe(loadedConfig);
+              },
+              (e) => { throw 'Should not reach'; });
+    });
   });
 
   describe('empty paths', () => {