feat(core): allow custom selector when bootstrapping components (#15668)

- fixes #7136

PR Close #15668

packages/core/src/application_ref.ts

@@ -358,10 +358,15 @@ export abstract class ApplicationRef {
    * specified application component onto DOM elements identified by the [componentType]'s
    * selector and kicks off automatic change detection to finish initializing the component.
    *
+   * Optionally, a component can be mounted onto a DOM element that does not match the
+   * [componentType]'s selector.
+   *
    * ### Example
    * {@example core/ts/platform/platform.ts region='longform'}
    */
-  abstract bootstrap<C>(componentFactory: ComponentFactory<C>|Type<C>): ComponentRef<C>;
+  abstract bootstrap<C>(
+      componentFactory: ComponentFactory<C>|Type<C>,
+      rootSelectorOrNode?: string|any): ComponentRef<C>;
 
   /**
    * Invoke this method to explicitly process change detection and its side-effects.
@@ -491,7 +496,8 @@ export class ApplicationRef_ extends ApplicationRef {
     view.detachFromAppRef();
   }
 
-  bootstrap<C>(componentOrFactory: ComponentFactory<C>|Type<C>): ComponentRef<C> {
+  bootstrap<C>(componentOrFactory: ComponentFactory<C>|Type<C>, rootSelectorOrNode?: string|any):
+      ComponentRef<C> {
     if (!this._initStatus.done) {
       throw new Error(
           'Cannot bootstrap as there are still asynchronous initializers running. Bootstrap components in the `ngDoBootstrap` method of the root module.');
@@ -509,7 +515,8 @@ export class ApplicationRef_ extends ApplicationRef {
     const ngModule = componentFactory instanceof ComponentFactoryBoundToModule ?
         null :
         this._injector.get(NgModuleRef);
-    const compRef = componentFactory.create(Injector.NULL, [], componentFactory.selector, ngModule);
+    const selectorOrNode = rootSelectorOrNode || componentFactory.selector;
+    const compRef = componentFactory.create(Injector.NULL, [], selectorOrNode, ngModule);
 
     compRef.onDestroy(() => { this._unloadComponent(compRef); });
     const testability = compRef.injector.get(Testability, null);

packages/core/test/application_ref_spec.ts

@@ -30,11 +30,11 @@ export function main() {
 
     beforeEach(() => { mockConsole = new MockConsole(); });
 
-    function createRootEl() {
+    function createRootEl(selector = 'bootstrap-app') {
       const doc = TestBed.get(DOCUMENT);
       const rootEl = <HTMLElement>getDOM().firstChild(
-          getDOM().content(getDOM().createTemplate(`<bootstrap-app></bootstrap-app>`)));
-      const oldRoots = getDOM().querySelectorAll(doc, 'bootstrap-app');
+          getDOM().content(getDOM().createTemplate(`<${selector}></${selector}>`)));
+      const oldRoots = getDOM().querySelectorAll(doc, selector);
       for (let i = 0; i < oldRoots.length; i++) {
         getDOM().remove(oldRoots[i]);
       }
@@ -100,6 +100,34 @@ export function main() {
          expect(component.injector.get('hello')).toEqual('component');
        })));
 
+    it('should bootstrap a component with a custom selector',
+       async(inject([ApplicationRef, Compiler], (app: ApplicationRef, compiler: Compiler) => {
+         @Component({
+           selector: 'bootstrap-app',
+           template: '',
+         })
+         class SomeComponent {
+         }
+
+         @NgModule({
+           providers: [{provide: 'hello', useValue: 'component'}],
+           declarations: [SomeComponent],
+           entryComponents: [SomeComponent],
+         })
+         class SomeModule {
+         }
+
+         createRootEl('custom-selector');
+         const modFactory = compiler.compileModuleSync(SomeModule);
+         const module = modFactory.create(TestBed);
+         const cmpFactory =
+             module.componentFactoryResolver.resolveComponentFactory(SomeComponent) !;
+         const component = app.bootstrap(cmpFactory, 'custom-selector');
+
+         // The component should see the child module providers
+         expect(component.injector.get('hello')).toEqual('component');
+       })));
+
     describe('ApplicationRef', () => {
       beforeEach(() => { TestBed.configureTestingModule({imports: [createModule()]}); });
 

tools/public_api_guard/core/core.d.ts

@@ -131,7 +131,7 @@ export declare abstract class ApplicationRef {
     readonly abstract isStable: Observable<boolean>;
     readonly abstract viewCount: number;
     abstract attachView(view: ViewRef): void;
-    abstract bootstrap<C>(componentFactory: ComponentFactory<C> | Type<C>): ComponentRef<C>;
+    abstract bootstrap<C>(componentFactory: ComponentFactory<C> | Type<C>, rootSelectorOrNode?: string | any): ComponentRef<C>;
     abstract detachView(view: ViewRef): void;
     abstract tick(): void;
 }