feat(bootstrap): add platform and app initializers

Often some init logic needs to run when a platform or an application is boostrapped.
For example, boostraping a platform requires initializing the dom adapter.
Now, it can be done as follows:

new Provider(PLATFORM_INITIALIZER, {useValue: initDomAdapter, multi: true}),

All platform initializers will be run after the platform injector has been created.

Similarly, all application initializers will be run after the app injector has been
created.

Closes #5355

modules/angular2/src/core/application_ref.ts

@@ -4,7 +4,9 @@ import {provide, Provider, Injector, OpaqueToken} from 'angular2/src/core/di';
 import {
   APP_COMPONENT_REF_PROMISE,
   APP_COMPONENT,
-  APP_ID_RANDOM_PROVIDER
+  APP_ID_RANDOM_PROVIDER,
+  PLATFORM_INITIALIZER,
+  APP_INITIALIZER
 } from './application_tokens';
 import {
   Promise,
@@ -30,7 +32,6 @@ import {wtfLeave, wtfCreateScope, WtfScopeFn} from './profile/profile';
 import {ChangeDetectorRef} from 'angular2/src/core/change_detection/change_detector_ref';
 import {lockDevMode} from 'angular2/src/facade/lang';
 
-
 /**
  * Construct providers specific to an individual root component.
  */
@@ -103,15 +104,32 @@ export function platform(providers?: Array<Type | Provider | any[]>): PlatformRe
   }
 }
 
+/**
+ * Dispose the existing platform.
+ */
+export function disposePlatform(): void {
+  if (isPresent(_platform)) {
+    _platform.dispose();
+    _platform = null;
+  }
+}
+
 function _createPlatform(providers?: Array<Type | Provider | any[]>): PlatformRef {
   _platformProviders = providers;
-  _platform = new PlatformRef_(Injector.resolveAndCreate(providers), () => {
+  let injector = Injector.resolveAndCreate(providers);
+  _platform = new PlatformRef_(injector, () => {
     _platform = null;
     _platformProviders = null;
   });
+  _runPlatformInitializers(injector);
   return _platform;
 }
 
+function _runPlatformInitializers(injector: Injector): void {
+  let inits: Function[] = injector.getOptional(PLATFORM_INITIALIZER);
+  if (isPresent(inits)) inits.forEach(init => init());
+}
+
 /**
  * The Angular platform is the entry point for Angular on a web page. Each page
  * has exactly one platform, and services (such as reflection) which are common
@@ -236,11 +254,12 @@ export class PlatformRef_ extends PlatformRef {
     });
     app = new ApplicationRef_(this, zone, injector);
     this._applications.push(app);
+    _runAppInitializers(injector);
     return app;
   }
 
   dispose(): void {
-    this._applications.forEach((app) => app.dispose());
+    ListWrapper.clone(this._applications).forEach((app) => app.dispose());
     this._disposeListeners.forEach((dispose) => dispose());
     this._dispose();
   }
@@ -249,6 +268,11 @@ export class PlatformRef_ extends PlatformRef {
   _applicationDisposed(app: ApplicationRef): void { ListWrapper.remove(this._applications, app); }
 }
 
+function _runAppInitializers(injector: Injector): void {
+  let inits: Function[] = injector.getOptional(APP_INITIALIZER);
+  if (isPresent(inits)) inits.forEach(init => init());
+}
+
 /**
  * A reference to an Angular application running on a page.
  *
@@ -439,7 +463,7 @@ export class ApplicationRef_ extends ApplicationRef {
 
   dispose(): void {
     // TODO(alxhub): Dispose of the NgZone.
-    this._rootComponents.forEach((ref) => ref.dispose());
+    ListWrapper.clone(this._rootComponents).forEach((ref) => ref.dispose());
     this._disposeListeners.forEach((dispose) => dispose());
     this._platform._applicationDisposed(this);
   }

modules/angular2/src/core/application_tokens.ts

@@ -48,3 +48,14 @@ export const APP_ID_RANDOM_PROVIDER: Provider =
 function _randomChar(): string {
   return StringWrapper.fromCharCode(97 + Math.floor(Math.random() * 25));
 }
+
+/**
+ * A function that will be executed when a platform is initialized.
+ */
+export const PLATFORM_INITIALIZER: OpaqueToken =
+    CONST_EXPR(new OpaqueToken("Platform Initializer"));
+
+/**
+ * A function that will be executed when an application is initialized.
+ */
+export const APP_INITIALIZER: OpaqueToken = CONST_EXPR(new OpaqueToken("Application Initializer"));

modules/angular2/src/platform/browser_common.ts

@@ -11,13 +11,13 @@ import {
   reflector,
   APPLICATION_COMMON_PROVIDERS,
   PLATFORM_COMMON_PROVIDERS,
-  EVENT_MANAGER_PLUGINS
+  EVENT_MANAGER_PLUGINS,
+  PLATFORM_INITIALIZER
 } from "angular2/core";
 import {COMMON_DIRECTIVES, COMMON_PIPES, FORM_PROVIDERS} from "angular2/common";
 import {Renderer} from 'angular2/render';
 import {Testability} from 'angular2/src/core/testability/testability';
 
-// TODO change these imports once dom_adapter is moved out of core
 import {DOM} from 'angular2/src/core/dom/dom_adapter';
 import {DomEventsPlugin} from 'angular2/src/platform/dom/events/dom_events';
 import {KeyEventsPlugin} from 'angular2/src/platform/dom/events/key_events';
@@ -42,8 +42,10 @@ export {
 export {By} from 'angular2/src/platform/browser/debug/by';
 export {BrowserDomAdapter} from './browser/browser_adapter';
 
-export const BROWSER_PROVIDERS: Array<any /*Type | Provider | any[]*/> =
-    CONST_EXPR([PLATFORM_COMMON_PROVIDERS]);
+export const BROWSER_PROVIDERS: Array<any /*Type | Provider | any[]*/> = CONST_EXPR([
+  PLATFORM_COMMON_PROVIDERS,
+  new Provider(PLATFORM_INITIALIZER, {useValue: initDomAdapter, multi: true}),
+]);
 
 function _exceptionHandler(): ExceptionHandler {
   return new ExceptionHandler(DOM, false);
@@ -73,7 +75,6 @@ export const BROWSER_APP_COMMON_PROVIDERS: Array<any /*Type | Provider | any[]*/
 ]);
 
 export function initDomAdapter() {
-  // TODO: refactor into a generic init function
   BrowserDomAdapter.makeCurrent();
   wtfInit();
   BrowserGetTestability.init();