feat(create-injection-token): expose initializer provider function fo…

…r root tokens

docs/src/content/docs/utilities/Injectors/create-injection-token.md

@@ -196,3 +196,19 @@ export class Counter {
 	}
 }
 ```
+
+## Environment Initializer
+
+Sometimes, it is required for **root** tokens to be initialized in `ENVIRONMENT_INITIALIZER`. Instead of providing `ENVIRONMENT_INITIALIZER` manually, we can retrieve the initializer provider function from `createInjectionToken` to do so.
+
+:::caution
+The **initializer provider** function is a **noop** for non-root tokens.
+:::
+
+```ts
+const [injectOne /* skip provider fn */ /* skip the token */, , , provideOneInitializer] = createInjectionToken(() => 1);
+
+bootstrapApplication(App, {
+	providers: [provideOneInitializer()],
+});
+```

libs/ngxtension/create-injection-token/src/create-injection-token.ts

@@ -1,4 +1,5 @@
 import {
+	ENVIRONMENT_INITIALIZER,
 	InjectionToken,
 	inject,
 	runInInjectionContext,
@@ -84,7 +85,8 @@ export type CreateInjectionTokenReturn<
 > = [
 	InjectFn<TFactoryReturn>,
 	ProvideFn<TNoop, TFactoryReturn>,
-	InjectionToken<TFactoryReturn>
+	InjectionToken<TFactoryReturn>,
+	() => Provider | void
 ];
 
 function createInjectFn<TValue>(token: InjectionToken<TValue>) {
@@ -198,14 +200,23 @@ createInjectionToken is creating a root InjectionToken but an external token is
 			},
 		});
 
+		const injectFn = createInjectFn(
+			token
+		) as CreateInjectionTokenReturn<TFactoryReturn>[0];
+
 		return [
-			createInjectFn(token) as CreateInjectionTokenReturn<TFactoryReturn>[0],
+			injectFn,
 			createProvideFn(
 				token,
 				factory,
 				opts as CreateProvideFnOptions<TFactory, TFactoryDeps>
 			) as CreateInjectionTokenReturn<TFactoryReturn>[1],
 			token,
+			() => ({
+				provide: ENVIRONMENT_INITIALIZER,
+				useValue: () => injectFn(),
+				multi: true,
+			}),
 		];
 	}
 
@@ -219,6 +230,7 @@ createInjectionToken is creating a root InjectionToken but an external token is
 			opts as CreateProvideFnOptions<TFactory, TFactoryDeps>
 		) as CreateInjectionTokenReturn<TFactoryReturn>[1],
 		token,
+		() => {},
 	];
 }
 
@@ -244,5 +256,6 @@ export function createNoopInjectionToken<
 			(options || {}) as CreateProvideFnOptions<() => void, []>
 		) as CreateInjectionTokenReturn<TReturn, true>[1],
 		token,
+		() => {},
 	] as CreateInjectionTokenReturn<TReturn, true>;
 }