Unexpected circular dependency error

[LandazuriPaul]

I'm submitting a...

[ ] Regression
[x] Bug report
[ ] Feature request
[ ] Documentation issue or request

Current behavior

Nest throws an error about a circular dependency that doesn't exist. Here is the error thrown:
Nest cannot create the module instance. Often, this is because of a circular dependency between modules. Use forwardRef() to avoid it. (Read more https://docs.nestjs.com/fundamentals/circular-dependency.) Scope [APIModule -> AuthModule]

Expected behavior

From what I understand about circular dependency, there isn't any in the situation described, so Nest should be able to create the module instance.

Minimal reproduction of the problem with instructions

• I've created a dumb repo to reproduce the error: https://github.com/LandazuriPaul/nest-circular-dependency-bug
• Here are the module declarations:

api.module.ts

import { Module } from '@nestjs/common';

import { AuthModule, UserModule } from '@modules';

@Module({
  imports: [
    AuthModule,
    UserModule,
  ],
})
export class APIModule {}

auth.module.ts

import { Module } from '@nestjs/common';

import { AuthService } from '@api/services';
import { UserModule } from '@modules';
import { UserService } from '@domain/services';

@Module({
  imports: [
    UserModule
  ],
  providers: [
    AuthService,
    UserService,
  ],
  exports: [AuthService]
})
export class AuthModule {}

user.module.ts

import { Module } from '@nestjs/common';

import { UserService } from '@domain/services';

@Module({
  providers: [UserService],
  exports: [UserService],
})
export class UserModule {}

---

And for more information, here are the 2 services:

auth.service.ts

import { Injectable, Logger } from '@nestjs/common';

import { UserService } from '@domain/services';

@Injectable()
export class AuthService {
  private logger = new Logger(AuthService.name);

  constructor(
    private readonly usersService: UserService,
  ) {}
}

user.service.ts

import {
  Injectable,
  Logger,
} from '@nestjs/common';

@Injectable()
export class UserService {
  private logger = new Logger(UserService.name);
}

Environment

Nest version: 5.4.0
Node version: 11.0.0

[LandazuriPaul]

Trying to solve my issue, I'm discovered that if I import the modules directly (instead of using the modules/index.ts with intermediate exports), Nest doesn't complain at all and everything works fine.

So as a fix, I've found a solution. I just have to replace my module imports with this:

api.module.ts

import { AuthModule } from '@modules/auth/auth.module';
import { UserModule } from '@modules/user/user.module';

...

auth.module.ts

import { UserModule } from '@modules/user/user.module';

...

---

But still, I'm curious to understand why there is an issue with my first approach. I guess I've misunderstood something about Nest dependencies or maybe it's not Nest related at all and just the way imports work in Node.js / TypeScript environment. And if so, I'm curious to know if there is a way to gather all declarations living in a directory (here, modules) in an index.ts. Because I feel that my initial approach was more developper-friendly, as I could import all my modules from a single point.

So if anyone has any input or explanation about this behaviour, it would be very welcomed! :)

And besides, the Nest framework and the way it is lead are very promising and interesting!

Dziękuję @kamilmysliwiec !

[kamilmysliwiec]

Dziękuje @LandazuriPaul! :)

I'm glad that you found a solution. Here you can read more about this issue: #1181

[LandazuriPaul]

Thanks for the issue reference!

I'll read about barrel files and its implications. I didn't know about all the outcomes tied to them.

[lock]

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