Angular 5 APP_INITIALIZER：提供者解析错误：无法实例化循环依赖

Question

在我的 Angular 应用程序启动之前，我正在使用 APP_INITIALIZER 令牌在页面加载时执行某些操作。我用于该逻辑的服务取决于我在CoreModule 中的另一项服务。

我知道这个错误正在发生，因为我将AuthService 注入到我的AppService 中，但是我不明白为什么这很重要。 AuthService 没有注入AppService，那它怎么是循环依赖呢？

这是我的错误：

> Uncaught Error: Provider parse errors: Cannot instantiate cyclic
> dependency! ApplicationRef ("[ERROR ->]"): in NgModule AppModule in
> ./AppModule@-1:-1 Cannot instantiate cyclic dependency! ApplicationRef
> ("[ERROR ->]"): in NgModule AppModule in ./AppModule@-1:-1
>     at NgModuleProviderAnalyzer.parse (compiler.js:19550)
>     at NgModuleCompiler.compile (compiler.js:20139)
>     at JitCompiler._compileModule (compiler.js:34437)
>     at eval (compiler.js:34368)
>     at Object.then (compiler.js:474)
>     at JitCompiler._compileModuleAndComponents (compiler.js:34366)
>     at JitCompiler.compileModuleAsync (compiler.js:34260)
>     at CompilerImpl.compileModuleAsync (platform-browser-dynamic.js:239)
>     at PlatformRef.bootstrapModule (core.js:5567)
>     at bootstrap (main.ts:13)

这是我的AppModule：

import { NgModule, APP_INITIALIZER } from '@angular/core';

import { AppService, AppServiceFactory } from './app.service';
import { CoreModule } from 'core';

@NgModule({
    imports: [
        // ...
        CoreModule,
        // ...
    ],
    providers: [
        AppService,
        {
            provide: APP_INITIALIZER,
            useFactory: AppServiceFactory,
            deps: [AppService],
            multi: true
        }
    ],
    declarations: [AppComponent],
    bootstrap: [AppComponent]
})
export class AppModule {}

这里是AppService：

import { Injectable } from '@angular/core';

import { finalize } from 'rxjs/operators';

import { AuthService } from 'core/services/auth/auth.service';

export function AppServiceFactory(appService: AppService): () => Promise<any> {
    return () => appService.doBeforeBootstrap();
}

@Injectable()
export class AppService {
    constructor(private authService: AuthService) {}

    doBeforeBootstrap(): Promise<any> {
        return new Promise(resolve => {
            this.authService.isLoggedIn().then((loggedIn: boolean) => {
                // If the user is logged in, resolve (do nothing).
                if (loggedIn) {
                    return resolve();
                }

                // Otherwise, refresh the users token before resolving.
                this.authService.refreshToken().pipe(
                    finalize(() => resolve())
                ).subscribe();
            });
        });
    }
}

有人知道为什么会出现这样的错误吗？

编辑（AuthService的依赖项）：

constructor(
    private ref: ApplicationRef,
    private router: Router,
    private http: HttpClient,
    // Other custom services that are NOT imported into AppService...
) {}

Answer 1

您为APP_INITIALIZER 提供一个工厂，该工厂依赖于AppService，该工厂依赖于AuthService，该工厂依赖于ApplicationRef，该工厂依赖于ApplicationInitStatus，该工厂依赖于APP_INITIALIZER...等等

请参阅第 398 行的 https://github.com/angular/angular/blob/5.2.9/packages/core/src/application_init.ts 和 https://github.com/angular/angular/blob/5.2.9/packages/core/src/application_ref.ts