Angular CLI依赖项 - 如果我不使用它，为什么需要安装@ angular / router？

Question

When I start a blank Angular CLI project, these dependencies from package.json look like not necessary, so I'm trying to remove them (as well as removing FormModules and HttpModules from imports):

@angular/forms": "^4.0.0",
@angular/http": "^4.0.0",
@angular/router": "^4.0.0",

But when I try build the project, I'm getting an error:

'ERROR in Could not resolve module @angular/router'

And what looks even more weird to me, after re-saving a file the project rebuilds successfully and it works.

Can somebody explain where is this hidden dependency from @angular/router?

My files:

app.modules.ts:

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';    
import { AppComponent } from './app.component';

@NgModule({
  declarations: [
    AppComponent
  ],
  imports: [
    BrowserModule
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule {}

app.component.ts:

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

@Component({
  selector: 'app-root',
  template: '<h1>test</h1>'
})
export class AppComponent {}

Answer 1

Angular cli uses @ngtool/webpack plugin that uses private API from @angular/compiler-cli to get lazy loaded routes

plugin.ts

const {__NGTOOLS_PRIVATE_API_2} = require('@angular/compiler-cli');

https://github.com/angular/angular-cli/blob/v1.0.1/packages/%40ngtools/webpack/src/plugin.ts#L7

// We need to run the `listLazyRoutes` the first time because it also navigates libraries
// and other things that we might miss using the findLazyRoutesInAst.
let discoveredLazyRoutes: LazyRouteMap = this.firstRun ?
__NGTOOLS_PRIVATE_API_2.listLazyRoutes({
  program: this._program,
  host: this._compilerHost,
  angularCompilerOptions: this._angularCompilerOptions,
  entryModule: this._entryModule
})
: this._findLazyRoutesInAst();

https://github.com/angular/angular-cli/blob/v1.0.1/packages/%40ngtools/webpack/src/plugin.ts#L492-L501

Notice this.firstRun .That's why you are getting the error on the first run.

@angular/compiler-cli/src/ngtools_impl.ts

const ROUTER_MODULE_PATH = '@angular/router';

https://github.com/angular/angular/blob/4.1.0/packages/compiler-cli/src/ngtools_impl.ts#L20

Here is reproduction

See also

• https://github.com/angular/angular-cli/issues/5967