feat: add a PLATFORM_ID token that provides a platform id Object. (#14647)

modules/@angular/core/src/application_tokens.ts

@@ -46,6 +46,12 @@ function _randomChar(): string {
  */
 export const PLATFORM_INITIALIZER = new InjectionToken<Array<() => void>>('Platform Initializer');
 
+/**
+ * A token that indicates an opaque platform id.
+ * @experimental
+ */
+export const PLATFORM_ID = new InjectionToken<Object>('Platform ID');
+
 /**
  * All callbacks provided via this token will be called for every component that is bootstrapped.
  * Signature of the callback:

modules/@angular/core/src/core.ts

@@ -16,7 +16,7 @@ export * from './version';
 export * from './util';
 export * from './di';
 export {createPlatform, assertPlatform, destroyPlatform, getPlatform, PlatformRef, ApplicationRef, enableProdMode, isDevMode, createPlatformFactory, NgProbeToken} from './application_ref';
-export {APP_ID, PACKAGE_ROOT_URL, PLATFORM_INITIALIZER, APP_BOOTSTRAP_LISTENER} from './application_tokens';
+export {APP_ID, PACKAGE_ROOT_URL, PLATFORM_INITIALIZER, PLATFORM_ID, APP_BOOTSTRAP_LISTENER} from './application_tokens';
 export {APP_INITIALIZER, ApplicationInitStatus} from './application_init';
 export * from './zone';
 export * from './render';

modules/@angular/core/src/platform_core_providers.ts

@@ -7,6 +7,7 @@
  */
 
 import {PlatformRef, PlatformRef_, createPlatformFactory} from './application_ref';
+import {PLATFORM_ID} from './application_tokens';
 import {Console} from './console';
 import {Provider} from './di';
 import {Reflector, reflector} from './reflection/reflection';
@@ -18,6 +19,8 @@ function _reflector(): Reflector {
 }
 
 const _CORE_PLATFORM_PROVIDERS: Provider[] = [
+  // Set a default platform name for platforms that don't set it explicitly.
+  {provide: PLATFORM_ID, useValue: 'unknown'},
   PlatformRef_,
   {provide: PlatformRef, useExisting: PlatformRef_},
   {provide: Reflector, useFactory: _reflector, deps: []},