angular - 在Angular 8+中实现ErrorHandler类会在运行时给出异常

Question

this snippet is from app.module.ts. I just created an angular 9 application 
 and tried to implement ErrorHandler class to catch error but it is showing 
 the error at run time and page does not load.

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

@NgModule({
  declarations: [
    AppComponent
  ],
  imports: [
    BrowserModule,
    AppRoutingModule
  ],
  providers: [
    {provide: ErrorHandler, useClass: MyErrorHandler}
  ],
  bootstrap: [AppComponent]
})

class MyErrorHandler implements ErrorHandler {
  handleError(error) {
    alert(error);
    // do something with the exception
  }
}
export class AppModule { }

Exception in browser:

ASSERTION ERROR: Type passed in is not NgModuleType, it does not have 'ɵmod' property.
    at throwError (core.js:1344)
    at assertNgModuleType (core.js:2951)
    at compileNgModuleFactory__POST_R3__ (core.js:42275)
    at PlatformRef.bootstrapModule (core.js:42663)
    at Module../src/main.ts (main.ts:11)
    at __webpack_require__ (bootstrap:79)
    at Object.0 (main.ts:12)
    at __webpack_require__ (bootstrap:79)
    at checkDeferredModules (bootstrap:45)
    at Array.webpackJsonpCallback [as push] (bootstrap:32)

Answer 1

将您的MyErrorHandler类移动到一个单独的文件中，并将其导入到AppModule中，它应该可以工作。
Angular使用 typescript 装饰器，这些装饰器在它们所属的每个类之上定义。在您的情况下，您要将装饰器@NgModule添加到类MyErrorHandler中，这样Angular找不到主AppModule的正确配置，这就是为什么在编译时会收到此类错误。