fix(core): export inject() from @angular/core (#22389)

inject() supports the ngInjectableDef-based configuration of the injector
(otherwise known as tree-shakeable services). It was missing from the
exported API of @angular/core, this PR adds it.

The test added here is correct in theory, but may pass accidentally due
to the decorator side-effect replacing the inject() call at runtime. An
upcoming compiler PR will strip reified decorators from the output
entirely.

Fixes #22388

PR Close #22389

Author: alxhub

packages/compiler-cli/integrationtest/bazel/injectable_def/app/src/dep.ts

@@ -0,0 +1,41 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import {Component, Injectable, NgModule} from '@angular/core';
+import {BrowserModule} from '@angular/platform-browser';
+import {ServerModule} from '@angular/platform-server';
+
+@Injectable()
+export class NormalService {
+}
+
+@Component({
+  selector: 'dep-app',
+  template: '{{found}}',
+})
+export class AppComponent {
+  found: boolean;
+  constructor(service: ShakeableService) { this.found = !!service.normal; }
+}
+
+@NgModule({
+  imports: [
+    BrowserModule.withServerTransition({appId: 'id-app'}),
+    ServerModule,
+  ],
+  declarations: [AppComponent],
+  bootstrap: [AppComponent],
+  providers: [NormalService],
+})
+export class DepAppModule {
+}
+
+@Injectable({scope: DepAppModule})
+export class ShakeableService {
+  constructor(readonly normal: NormalService) {}
+}

packages/compiler-cli/integrationtest/bazel/injectable_def/app/src/token.ts

@@ -6,19 +6,19 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {Component, Inject, InjectionToken, NgModule, forwardRef} from '@angular/core';
+import {Component, Inject, Injectable, InjectionToken, NgModule, forwardRef, inject} from '@angular/core';
 import {BrowserModule} from '@angular/platform-browser';
 import {ServerModule} from '@angular/platform-server';
 
-export interface IService { readonly data: string; }
+export interface IService { readonly dep: {readonly data: string;}; }
 
 @NgModule({})
 export class TokenModule {
 }
 
 export const TOKEN = new InjectionToken('test', {
   scope: TokenModule,
-  factory: () => new Service(),
+  factory: () => new Service(inject(Dep)),
 });
 
 
@@ -28,7 +28,7 @@ export const TOKEN = new InjectionToken('test', {
 })
 export class AppComponent {
   data: string;
-  constructor(@Inject(TOKEN) service: IService) { this.data = service.data; }
+  constructor(@Inject(TOKEN) service: IService) { this.data = service.dep.data; }
 }
 
 @NgModule({
@@ -37,10 +37,18 @@ export class AppComponent {
     ServerModule,
     TokenModule,
   ],
+  providers: [forwardRef(() => Dep)],
   declarations: [AppComponent],
   bootstrap: [AppComponent],
 })
 export class TokenAppModule {
 }
 
-export class Service { readonly data = 'fromToken'; }
+@Injectable()
+export class Dep {
+  readonly data = 'fromToken';
+}
+
+export class Service {
+  constructor(readonly dep: Dep) {}
+}

packages/compiler-cli/integrationtest/bazel/injectable_def/app/test/app_spec.ts

@@ -9,6 +9,7 @@
 import {enableProdMode} from '@angular/core';
 import {renderModuleFactory} from '@angular/platform-server';
 import {BasicAppModuleNgFactory} from 'app_built/src/basic.ngfactory';
+import {DepAppModuleNgFactory} from 'app_built/src/dep.ngfactory';
 import {HierarchyAppModuleNgFactory} from 'app_built/src/hierarchy.ngfactory';
 import {RootAppModuleNgFactory} from 'app_built/src/root.ngfactory';
 import {SelfAppModuleNgFactory} from 'app_built/src/self.ngfactory';
@@ -66,4 +67,14 @@ describe('ngInjectableDef Bazel Integration', () => {
       done();
     });
   });
+
+  it('can inject dependencies', done => {
+    renderModuleFactory(DepAppModuleNgFactory, {
+      document: '<dep-app></dep-app>',
+      url: '/',
+    }).then(html => {
+      expect(html).toMatch(/>true<\//);
+      done();
+    });
+  });
 });

packages/core/src/core_private_export.ts

@@ -12,6 +12,7 @@ export {devModeEqual as ɵdevModeEqual} from './change_detection/change_detectio
 export {isListLikeIterable as ɵisListLikeIterable} from './change_detection/change_detection_util';
 export {ChangeDetectorStatus as ɵChangeDetectorStatus, isDefaultChangeDetectionStrategy as ɵisDefaultChangeDetectionStrategy} from './change_detection/constants';
 export {Console as ɵConsole} from './console';
+export {setCurrentInjector as ɵsetCurrentInjector} from './di/injector';
 export {ComponentFactory as ɵComponentFactory} from './linker/component_factory';
 export {CodegenComponentFactoryResolver as ɵCodegenComponentFactoryResolver} from './linker/component_factory_resolver';
 export {ReflectionCapabilities as ɵReflectionCapabilities} from './reflection/reflection_capabilities';

packages/core/src/di.ts

@@ -17,7 +17,7 @@ export {defineInjectable, Injectable, InjectableDecorator, InjectableProvider, I
 
 export {forwardRef, resolveForwardRef, ForwardRefFn} from './di/forward_ref';
 
-export {InjectFlags, Injector} from './di/injector';
+export {inject, InjectFlags, Injector} from './di/injector';
 export {ReflectiveInjector} from './di/reflective_injector';
 export {StaticProvider, ValueProvider, ExistingProvider, FactoryProvider, Provider, TypeProvider, ClassProvider} from './di/provider';
 export {ResolvedReflectiveFactory, ResolvedReflectiveProvider} from './di/reflective_provider';

packages/core/src/di/injector.ts

@@ -410,6 +410,20 @@ export function setCurrentInjector(injector: Injector | null): Injector|null {
   return former;
 }
 
+/**
+ * Injects a token from the currently active injector.
+ *
+ * This function must be used in the context of a factory function such as one defined for an
+ * `InjectionToken`, and will throw an error if not called from such a context. For example:
+ *
+ * {@example core/di/ts/injector_spec.ts region='ShakeableInjectionToken'}
+ *
+ * Within such a factory function `inject` is utilized to request injection of a dependency, instead
+ * of providing an additional array of dependencies as was common to do with `useFactory` providers.
+ * `inject` is faster and more type-safe.
+ *
+ * @experimental
+ */
 export function inject<T>(
     token: Type<T>| InjectionToken<T>, notFoundValue?: undefined, flags?: InjectFlags): T;
 export function inject<T>(

packages/examples/core/di/ts/injector_spec.ts

@@ -6,7 +6,25 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {InjectionToken, Injector, ReflectiveInjector} from '@angular/core';
+import {APP_ROOT_SCOPE, InjectFlags, InjectionToken, Injector, ReflectiveInjector, Type, inject, ɵsetCurrentInjector as setCurrentInjector} from '@angular/core';
+
+class MockRootScopeInjector implements Injector {
+  constructor(readonly parent: Injector) {}
+
+  get<T>(
+      token: Type<T>|InjectionToken<T>, defaultValue?: any,
+      flags: InjectFlags = InjectFlags.Default): T {
+    if ((token as any).ngInjectableDef && (token as any).ngInjectableDef.scope === APP_ROOT_SCOPE) {
+      const old = setCurrentInjector(this);
+      try {
+        return (token as any).ngInjectableDef.factory();
+      } finally {
+        setCurrentInjector(old);
+      }
+    }
+    return this.parent.get(token, defaultValue, flags);
+  }
+}
 
 {
   describe('injector metadata examples', () => {
@@ -37,5 +55,25 @@ import {InjectionToken, Injector, ReflectiveInjector} from '@angular/core';
       expect(url).toBe('http://localhost');
       // #enddocregion
     });
+
+    it('injects a tree-shaekable InjectionToken', () => {
+      class MyDep {}
+      const injector = new MockRootScopeInjector(ReflectiveInjector.resolveAndCreate([MyDep]));
+
+      // #docregion ShakeableInjectionToken
+      class MyService {
+        constructor(readonly myDep: MyDep) {}
+      }
+
+      const MY_SERVICE_TOKEN = new InjectionToken<MyService>('Manually constructed MyService', {
+        scope: APP_ROOT_SCOPE,
+        factory: () => new MyService(inject(MyDep)),
+      });
+
+      const instance = injector.get(MY_SERVICE_TOKEN);
+      expect(instance instanceof MyService).toBeTruthy();
+      expect(instance.myDep instanceof MyDep).toBeTruthy();
+      // #enddocregion
+    });
   });
 }

tools/public_api_guard/core/core.d.ts

@@ -447,6 +447,9 @@ export interface HostDecorator {
 /** @stable */
 export declare const HostListener: HostListenerDecorator;
 
+/** @experimental */
+export declare function inject<T>(token: Type<T> | InjectionToken<T>, notFoundValue?: undefined, flags?: InjectFlags): T;
+
 /** @stable */
 export declare const Inject: InjectDecorator;