I recently came across a unique situation. I am using NestJS, TypeOrm and Postgres.

I have a DynamicModule called CoreModule that is registered in the AppModule as following:

@Module({
  imports: [
    ...,
    CoreModule.register(),
    ...,
  ]
})

This core module registers some typeorm entities and repositories (custom, in a separate file) as following:

export class CoreModule {
  static register(): DynamicModule {
    return {
      module: CoreModule,
      imports: [
        ...,
        TypeOrmModule.forRootAsync({
          ...,
        }),
        TypeOrmModule.forFeature([
          ARepository,
          BRepository,
          CRepository,
          AEntity,
          BEntity,
          CEntity,
        ]),
      ],
      exports: [TypeOrmModule],
    };
  }
}

The repositories I created look like this (I followed this stackoverflow answer How to create custom (separate file) repository in NestJS 9 with TypeORM 0.3.x)

import { Injectable } from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { Repository } from 'typeorm';

@Injectable()
export class ARepository extends Repository<AEntity> {
  constructor(
    @InjectRepository(AEntity)
    private aRepository: Repository<AEntity>
  ) {
    super(aRepository.target, aRepository.manager, aRepository.queryRunner);
  }

  async customFunctionA() {}

  async customFunctionB() {}
}

I use this as following in one of the services:

@Injectable()
export class SomeService {
  constructor(
    private readonly aRepository: ARepository,
  ) {}

  public async someFunction() {
    return this.aRepository.customFunctionA();
  }

Now when I try to use this CustomRepository and call aRepository.customFunctionA or aRepository.customFunctionB I get an error this.aRepository.customFunctionA is not a function. I checked and found that this.aRepository has only has only three properties (target, manager and queryRunner) I think these come from Repository that I extend but none of the custom function I define in the repository are there.

Furthermore, if I remove the ARepository from TypeOrmModule.forFeature([]) argument array and add it to all modules that use it in like a normal injectable class, it works fine (I see custom functions).

My question is, why is doing TypeOrmModule.forFeature([]) not working here, what am I doing wrong and what should be avoided with forFeature in future?

I have found a solution as mentioned above in my explanation but do not understand why the initial code doesn’t work and if there is a better way to solve it.