Nest.js: how to override providers in an imported module?

Question

Code example

Third party library

@Module({ providers: [AService] exports: [AService] }) export class AModule { } @Module({ imports: [AModule], providers: [BService] exports: [BService] }) export class BModule { }

My code

@Module({ imports: [BModule], providers: [CService] }) export class CModule { }

Question

How can I override/replace the AService provider from my code? (without third party library patching)

Answer 1

Following on from my comment, this is how you would go about making a dynamic module with a dynamic provider

export interface ProviderInterface {
  handle(): void;
}

@Injectable()
class SomeHandlingProvider {
  constructor(@Inject('MY_DYNAMIC_PROVIDER') private readonly dynamicProvider: ProviderInterface) {}
  handle(): void {
    this.dynamicProvider.handle();
  }
}

@Module({})
export class AModule {
  public static forRoot(provider: ProviderInstance): DynamicModule {
    return {
       module: AModule,
       providers: [
         {
           provide: 'MY_DYNAMIC_PROVIDER',
           useClass: provider,
         },
         SomeHandlingProvider,
      ],
    };
  }
}

Then you can use like this

class GenericDynamicProviderExample implements ProviderInterface {
  handle(): void {
    console.log('hello');
  }
}

@Module({
  imports: [
    AModule.forRoot(GenericDynamicProviderExample),
  ],
})
export class BModule {}