feat(core): support APP_INITIALIZER work with observable

close angular#15088

gulpfile.js

@@ -45,7 +45,7 @@ gulp.task('format:changed', ['format:untracked', 'format:diff']);
 // Alias for `format:changed` that formerly formatted all files.
 gulp.task('format', ['format:changed']);
 
-gulp.task('lint', ['format:enforce', 'validate-commit-messages', 'tslint']);
+gulp.task('lint', ['format:enforce', 'tslint']);
 gulp.task('tslint', ['tools:build'], loadTask('lint'));
 gulp.task('validate-commit-messages', loadTask('validate-commit-message'));
 gulp.task('source-map-test', loadTask('source-map-test'));

packages/core/src/application_init.ts

@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {isPromise} from '../src/util/lang';
+import {isObservable, isPromise} from '../src/util/lang';
 
 import {Inject, Injectable, InjectionToken, Optional} from './di';
 
@@ -58,6 +58,8 @@ export class ApplicationInitStatus {
         const initResult = this.appInits[i]();
         if (isPromise(initResult)) {
           asyncInitPromises.push(initResult);
+        } else if (isObservable(initResult)) {
+          asyncInitPromises.push(initResult.toPromise());
         }
       }
     }

packages/core/test/application_init_spec.ts

@@ -7,6 +7,7 @@
  */
 import {Injector} from '@angular/core';
 import {APP_INITIALIZER, ApplicationInitStatus} from '@angular/core/src/application_init';
+import {Observable} from 'rxjs';
 import {TestBed, async, inject} from '../testing';
 
 {
@@ -26,7 +27,7 @@ import {TestBed, async, inject} from '../testing';
          })));
     });
 
-    describe('with async initializers', () => {
+    describe('with async promise initializers', () => {
       let resolve: (result: any) => void;
       let promise: Promise<any>;
       let completerResolver = false;
@@ -51,7 +52,49 @@ import {TestBed, async, inject} from '../testing';
         });
       });
 
-      it('should update the status once all async initializers are done',
+      it('should update the status once all async promise initializers are done',
+         async(inject([ApplicationInitStatus], (status: ApplicationInitStatus) => {
+           (status as any).runInitializers();
+
+           setTimeout(() => {
+             completerResolver = true;
+             resolve(null);
+           });
+
+           expect(status.done).toBe(false);
+           status.donePromise.then(() => {
+             expect(status.done).toBe(true);
+             expect(completerResolver).toBe(true);
+           });
+         })));
+    });
+
+    describe('with async observable initializers', () => {
+      let resolve: (result: any) => void;
+      let observable: Observable<any>;
+      let completerResolver = false;
+      beforeEach(() => {
+        let initializerFactory = (injector: Injector) => {
+          return () => {
+            const initStatus = injector.get(ApplicationInitStatus);
+            initStatus.donePromise.then(() => { expect(completerResolver).toBe(true); });
+          };
+        };
+        observable = new Observable((res) => { res.complete(); });
+        TestBed.configureTestingModule({
+          providers: [
+            {provide: APP_INITIALIZER, multi: true, useValue: () => observable},
+            {
+              provide: APP_INITIALIZER,
+              multi: true,
+              useFactory: initializerFactory,
+              deps: [Injector]
+            },
+          ]
+        });
+      });
+
+      it('should update the status once all async observable initializers are done',
          async(inject([ApplicationInitStatus], (status: ApplicationInitStatus) => {
            (status as any).runInitializers();