angular - Error: Unexpected value 'undefined' imported by the module

Question

I'm getting this error after migrating to NgModule, the error doesn't help too much, any advice please?

Error: Error: Unexpected value 'undefined' imported by the module 'AppModule'
        at new BaseException (http://localhost:5555/node_modules/@angular/compiler/bundles/compiler.umd.js:5116:27)
        at eval (http://localhost:5555/node_modules/@angular/compiler/bundles/compiler.umd.js:13231:35)
        at Array.forEach (native)
        at CompileMetadataResolver.getNgModuleMetadata (http://localhost:5555/node_modules/@angular/compiler/bundles/compiler.umd.js:13215:48)
        at RuntimeCompiler._compileComponents (http://localhost:5555/node_modules/@angular/compiler/bundles/compiler.umd.js:15845:51)
        at RuntimeCompiler._compileModuleAndComponents (http://localhost:5555/node_modules/@angular/compiler/bundles/compiler.umd.js:15769:41)
        at RuntimeCompiler.compileModuleAsync (http://localhost:5555/node_modules/@angular/compiler/bundles/compiler.umd.js:15746:25)
        at PlatformRef_._bootstrapModuleWithZone (http://localhost:5555/node_modules/@angular/core/bundles/core.umd.js:9991:29)
        at PlatformRef_.bootstrapModule (http://localhost:5555/node_modules/@angular/core/bundles/core.umd.js:9984:25)
        at Object.eval (http://localhost:5555/app/main.js:8:53)
    Evaluating http://localhost:5555/app/main.js
    Error loading http://localhost:5555/app/main.js "Report this error at https://github.com/mgechev/angular2-seed/issues"(anonymous function) @ contracts:142ZoneDelegate.invoke @ zone.js?1472711930202:332Zone.run @ zone.js?1472711930202:225(anonymous function) @ zone.js?1472711930202:586ZoneDelegate.invokeTask @ zone.js?1472711930202:365Zone.runTask @ zone.js?1472711930202:265drainMicroTaskQueue @ zone.js?1472711930202:491ZoneTask.invoke @ zone.js?1472711930202:435

app.module.ts:

    import { NgModule } from '@angular/core';
    import { BrowserModule } from '@angular/platform-browser';
    import { APP_BASE_HREF } from '@angular/common';
    import { RouterModule } from '@angular/router';
    import { HttpModule } from '@angular/http';
    import { AppComponent } from './app.component';
    import { routes } from './app.routes';

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

    //dgf ng2-translate
    import { TRANSLATE_PROVIDERS, TranslateLoader, TranslateStaticLoader, MissingTranslationHandler } from 'ng2-translate/ng2-translate';
    import { HTTP_PROVIDERS, Http } from '@angular/http';
    import { FormsModule,ReactiveFormsModule } from '@angular/forms';
    import { TranslationNotFoundHandler } from './shared/common/TranslationNotFoundHandler';
    //dgf ng2-translate END

    import {CalendarModule,DataTableModule,DialogModule,PanelModule} from 'primeng/primeng';

    import {TranslateModule} from 'ng2-translate/ng2-translate';

    import { AuthGuard,AppConfigService,AppConfig,DateHelper,ThemeComponent,ToolbarComponent, RemoveHostTagDirective } from './index';
    import { HomeComponent,MessagesExampleComponent,PrimeNgHomeComponent,CalendarComponent,Ng2BootstrapExamplesComponent,DatepickerDemoComponent,UserListComponent,UserEditComponent,ContractListComponent,AboutComponent } from './index';


@NgModule({
  imports: [BrowserModule, HttpModule, RouterModule.forRoot(routes), /* AboutModule, HomeModule, SharedModule.forRoot()*/
          FormsModule,
          ReactiveFormsModule,
          //third-party
          ,TranslateModule.forRoot() //,
          //third-party PRIMENG
          ,CalendarModule,DataTableModule,DialogModule,PanelModule
  ],
  declarations: [
    AppComponent,ThemeComponent, ToolbarComponent, RemoveHostTagDirective,
    HomeComponent,MessagesExampleComponent,PrimeNgHomeComponent,CalendarComponent,Ng2BootstrapExamplesComponent,DatepickerDemoComponent,UserListComponent,UserEditComponent,ContractListComponent,AboutComponent
  ],
  providers: [{
      provide: APP_BASE_HREF,
      useValue: '<%= APP_BASE %>'
    },
    FormsModule,
    ReactiveFormsModule,
    provide(TranslateLoader, { //DGF ng2-translate
          useFactory: (http: Http) => new TranslateStaticLoader(http, 'assets/i18n', '.json'),
          deps: [Http]
      }),
    provide(MissingTranslationHandler, { useClass: TranslationNotFoundHandler }), //DGF ng2-translate

    AuthGuard,AppConfigService,AppConfig,
    DateHelper
  ],
  bootstrap: [AppComponent]
})

export class AppModule { }

Answer 1

For anyone facing this same error, my situation was that I have double commas in the imports section

imports: [
      BrowserModule,
      HttpModule,
      FormsModule,
      RouterModule.forRoot(appRoutes), , // <-- this was the error
      // .... 
],