Angular 9“错误：此构造函数与依赖注入不兼容。”

Question

这个奇怪的错误，我不记得在常春藤之前看到过，在使用最新的 Angular 9 CLI 创建的新应用程序的设置中弹出。看起来这可能是 Ivy 的错误？任何关于如何修复的想法将不胜感激。

ng 测试的错误结果

Error: This constructor was not compatible with Dependency Injection.
    at Module.??invalidFactory (http://localhost:9876/_karma_webpack_/node_modules/@angular/core/__ivy_ngcc__/fesm5/core.js:14150:1)
    at Object.Router_Factory [as factory] (http://localhost:9876/_karma_webpack_/node_modules/@angular/router/__ivy_ngcc__/fesm5/router.js:4404:67)
    at R3Injector.push../node_modules/@angular/core/__ivy_ngcc__/fesm5/core.js.R3Injector.hydrate (http://localhost:9876/_karma_webpack_/node_modules/@angular/core/__ivy_ngcc__/fesm5/core.js:11425:1)
    at R3Injector.push../node_modules/@angular/core/__ivy_ngcc__/fesm5/core.js.R3Injector.get (http://localhost:9876/_karma_webpack_/node_modules/@angular/core/__ivy_ngcc__/fesm5/core.js:11247:1)
    at injectInjectorOnly (http://localhost:9876/_karma_webpack_/node_modules/@angular/core/__ivy_ngcc__/fesm5/core.js:787:1)
    at ??inject (http://localhost:9876/_karma_webpack_/node_modules/@angular/core/__ivy_ngcc__/fesm5/core.js:792:1)
    at Object.AuthService_Factory [as factory] (ng:///AuthService/?fac.js:5:39)
    at R3Injector.push../node_modules/@angular/core/__ivy_ngcc__/fesm5/core.js.R3Injector.hydrate (http://localhost:9876/_karma_webpack_/node_modules/@angular/core/__ivy_ngcc__/fesm5/core.js:11425:1)
    at R3Injector.push../node_modules/@angular/core/__ivy_ngcc__/fesm5/core.js.R3Injector.get (http://localhost:9876/_karma_webpack_/node_modules/@angular/core/__ivy_ngcc__/fesm5/core.js:11247:1)
    at NgModuleRef$1.push../node_modules/@angular/core/__ivy_ngcc__/fesm5/core.js.NgModuleRef$1.get (http://localhost:9876/_karma_webpack_/node_modules/@angular/core/__ivy_ngcc__/fesm5/core.js:24218:1)

Error: Expected undefined to be truthy.
    at <Jasmine>
    at UserContext.<anonymous> (http://localhost:9876/_karma_webpack_/src/app/shared/components/header/header.component.spec.ts:25:23)
    at ZoneDelegate.invoke (http://localhost:9876/_karma_webpack_/node_modules/zone.js/dist/zone.js:396:1)
    at ProxyZoneSpec.onInvoke (http://localhost:9876/_karma_webpack_/node_modules/zone.js/dist/zone-testing.js:305:1)

app.component.ts

import { Component, HostBinding } from '@angular/core';
import { AuthService, ScreenService, AppInfoService } from './shared/services';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.scss'],
})
export class AppComponent {
  @HostBinding('class') get getClass() {
    return Object.keys(this.screen.sizes)
      .filter(cl => this.screen.sizes[cl])
      .join(' ');
  }

  constructor(
    private authService: AuthService,
    private screen: ScreenService,
    public appInfo: AppInfoService,
  ) {}

  isAuthorized() {
    return this.authService.isLoggedIn;
  }
}

app.component.spec.ts

import { async, ComponentFixture, TestBed } from '@angular/core/testing';
import { Router } from '@angular/router';

import { AppComponent } from './app.component';
import { AuthService } from './shared/services';

describe('AppComponent', () => {
  let component: AppComponent;
  let fixture: ComponentFixture<AppComponent>;

  beforeEach(async(() => {
    TestBed.configureTestingModule({
      declarations: [AppComponent],
      providers: [AuthService, Router],
    }).compileComponents();
  }));

  beforeEach(() => {
    fixture = TestBed.createComponent(AppComponent);
    component = fixture.componentInstance;
    fixture.detectChanges();
  });

  it('should create', () => {
    expect(component).toBeTruthy();
  });
});

package.json 依赖项

  "dependencies": {
    "@angular/animations": "~9.0.2",
    "@angular/cdk": "^8.0.0",
    "@angular/common": "~9.0.2",
    "@angular/compiler": "~9.0.2",
    "@angular/core": "~9.0.2",
    "@angular/forms": "~9.0.2",
    "@angular/platform-browser": "~9.0.2",
    "@angular/platform-browser-dynamic": "~9.0.2",
    "@angular/router": "~9.0.2",
    "devextreme": "latest",
    "devextreme-angular": "latest",
    "rxjs": "~6.5.4",
    "tslib": "^1.10.0",
    "zone.js": "~0.10.2"
  },
  "devDependencies": {
    "@angular-devkit/build-angular": "~0.900.3",
    "@angular/cli": "~9.0.3",
    "@angular/compiler-cli": "~9.0.2",
    "@angular/language-service": "~9.0.2",
    "@types/jasmine": "~3.5.0",
    "@types/jasminewd2": "~2.0.3",
    "@types/node": "^12.11.1",
    "codelyzer": "^5.1.2",
    "devextreme-cli": "latest",
    "devextreme-themebuilder": "latest",
    "husky": "^4.2.3",
    "jasmine-core": "~3.5.0",
    "jasmine-spec-reporter": "~4.2.1",
    "karma": "~4.3.0",
    "karma-chrome-launcher": "~3.1.0",
    "karma-coverage-istanbul-reporter": "~2.1.0",
    "karma-jasmine": "~2.0.1",
    "karma-jasmine-html-reporter": "^1.4.2",
    "prettier": "^1.19.1",
    "pretty-quick": "^2.0.1",
    "protractor": "~5.4.3",
    "ts-node": "~8.3.0",
    "tslint": "~5.18.0",
    "tslint-config-prettier": "^1.18.0",
    "typescript": "~3.7.5",
    "webpack-bundle-analyzer": "^3.6.0"
  }

注意：修复NullInjectorErrorAuthService 和路由器后出现此错误。

Answer 1

您Router在测试中设置了as provider。那不是这样做的方法。

您应该RouterTestingModule在测试中导入以便能够访问它。

beforeEach(async(() => {
  TestBed.configureTestingModule({
    imports: [RouterTestingModule],
    declarations: [AppComponent],
    providers: [AuthService],
  }).compileComponents();
}));

我猜对于ivy和/或angular 9，他们从路由器服务中声明了`providedIn`，这样你就不能再在另一个模块中提供它了（无论如何你都不应该这样做:)）

背景资料：

查看源代码，您可以看到他们使用工厂以特殊方式注入路由器。路由器类本身只是一个没有@Injectable()装饰器的普通类。

Answer 2

此错误的另一个来源（与 OP 的问题无关）可能是当您有一个带有默认参数的构造函数参数时，例如：

constructor(someProp: string = 'propVal') {
    this.someProp = someProp;
}

您可以通过这样做来解决它：

constructor(@Inject('propVal') @Optional() someProp: string) {
    this.someProp = someProp;
}

Answer 3

如果您不小心尝试注入接口而不是服务，也可能会产生此错误，哈哈。

示例.interface.ts

export interface ExampleInterface {
  id: string
}

示例.service.ts

import { Injectable } from '@angular/core'

@Injectable({
  providedIn: 'root'
})
export class ExampleService {
  constructor() { }
}

依赖服务.ts

import { Injectable } from '@angular/core'

@Injectable({
  providedIn: 'root'
})
export class DependentService {
  constructor(
    private example: ExampleInterface // This is the error; should be ExampleService
  ) { }
}