Implementing ErrorHandler class in Angular 8+ gives the exception at run time

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)

move your MyErrorHandler class to a separate file and import it in your AppModule and it should work. — Yuriy Kravets
– Yuriy Kravets, Commented May 26, 2020 at 21:27

Yuriy Kravets · Accepted Answer · 2020-05-28 22:11:40Z

1

move your MyErrorHandler class to a separate file and import it in your AppModule and it should work.
Angular uses typescript decorators, which are defined above each class they belong to. In your case you were adding a decorator @NgModule to a class MyErrorHandler, that way Angular could not find proper configuration for main AppModule, and that's why you receive such error when compiling.

answered May 28, 2020 at 22:11

Yuriy Kravets

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1 Comment

Asad Naeem Over a year ago

Thanks for your great help and guidance.

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