refactor(router): Remove `defer` as it's not needed anymore (#38781)

This change contains the test from #38780 and also removes `defer` from
the `apply_redirects` logic because the change that introduced
`concatMap` instead of `map`...`concatAll` makes `defer` unnecessary.

PR Close #38781

packages/router/src/apply_redirects.ts

@@ -7,7 +7,7 @@
  */
 
 import {Injector, NgModuleRef} from '@angular/core';
-import {defer, EmptyError, from, Observable, Observer, of} from 'rxjs';
+import {EmptyError, from, Observable, Observer, of} from 'rxjs';
 import {catchError, combineAll, concatMap, first, map, mergeMap, tap} from 'rxjs/operators';
 
 import {LoadedRouterConfig, Route, Routes} from './config';
@@ -274,12 +274,11 @@ class ApplyRedirects {
       segments: UrlSegment[]): Observable<UrlSegmentGroup> {
     if (route.path === '**') {
       if (route.loadChildren) {
-        return defer(
+        return this.configLoader.load(ngModule.injector, route)
-            () => this.configLoader.load(ngModule.injector, route)
             .pipe(map((cfg: LoadedRouterConfig) => {
               route._loadedConfig = cfg;
               return new UrlSegmentGroup(segments, {});
-                      })));
+            }));
       }
 
       return of(new UrlSegmentGroup(segments, {}));

packages/router/test/integration.spec.ts

@@ -4090,7 +4090,7 @@ describe('Integration', () => {
         return of(delayMs).pipe(delay(delayMs), mapTo(true));
       }
 
-      @NgModule()
+      @NgModule({imports: [RouterModule.forChild([{path: '', component: BlankCmp}])]})
       class LoadedModule {
       }
 
@@ -4119,6 +4119,15 @@ describe('Integration', () => {
                 return false;
               }
             },
+            {
+              provide: 'returnFalseAndNavigate',
+              useFactory: (router: Router) => () => {
+                log.push('returnFalseAndNavigate');
+                router.navigateByUrl('/redirected');
+                return false;
+              },
+              deps: [Router]
+            },
             {
               provide: 'returnUrlTree',
               useFactory: (router: Router) => () => {
@@ -4132,7 +4141,23 @@ describe('Integration', () => {
         });
       });
 
-      it('should wait for higher priority guards to be resolved',
+      it('should only execute canLoad guards of routes being activated', fakeAsync(() => {
+           const router = TestBed.inject(Router);
+
+           router.resetConfig([
+             {path: 'lazy', canLoad: ['guard1'], loadChildren: () => of(LoadedModule)},
+             {path: 'redirected', component: SimpleCmp},
+             // canLoad should not run for this route because 'lazy' activates first
+             {path: '', canLoad: ['returnFalseAndNavigate'], loadChildren: () => of(LoadedModule)},
+           ]);
+
+           router.navigateByUrl('/lazy');
+           tick(5);
+           expect(log.length).toEqual(1);
+           expect(log).toEqual(['guard1']);
+         }));
+
+      it('should execute canLoad guards',
          fakeAsync(inject(
              [Router, NgModuleFactoryLoader],
              (router: Router, loader: SpyNgModuleFactoryLoader) => {