Name: oh-my-ai/nestjs
Rating: 99.7 (1 reviews)
Author: oh-my-ai

oh-my-ai/nestjs

NestJS architecture, dependency injection, validation, security, errors, testing, persistence, APIs, microservices, and deployment patterns with prioritized rule tiers and companion rule files.

1.12x

Quality

100%

Does it follow best practices?

Impact

97%

1.12x

Average score across 2 eval scenarios

Securityby

Advisory

Suggest reviewing before use

name:: arch-avoid-circular-deps
description:: Avoid Circular Dependencies — #1 cause of runtime crashes
title:: Avoid Circular Dependencies
impact:: CRITICAL
impactDescription:: #1 cause of runtime crashes
tags:: architecture, modules, dependencies

Avoid Circular Dependencies

Circular dependencies occur when Module A imports Module B, and Module B imports Module A (directly or transitively). NestJS can sometimes resolve these through forward references, but they indicate architectural problems and should be avoided. This is the #1 cause of runtime crashes in NestJS applications.

Incorrect (circular module imports):

// users.module.ts
@Module({
  imports: [OrdersModule], // Orders needs Users, Users needs Orders = circular
  providers: [UsersService],
  exports: [UsersService],
})
export class UsersModule {}

// orders.module.ts
@Module({
  imports: [UsersModule], // Circular dependency!
  providers: [OrdersService],
  exports: [OrdersService],
})
export class OrdersModule {}

Correct (extract shared logic or use events):

// Option 1: Extract shared logic to a third module
// shared.module.ts
@Module({
  providers: [SharedService],
  exports: [SharedService],
})
export class SharedModule {}

// users.module.ts
@Module({
  imports: [SharedModule],
  providers: [UsersService],
})
export class UsersModule {}

// orders.module.ts
@Module({
  imports: [SharedModule],
  providers: [OrdersService],
})
export class OrdersModule {}

// Option 2: Use events for decoupled communication
// users.service.ts
@Injectable()
export class UsersService {
  constructor(private eventEmitter: EventEmitter2) {}

  async createUser(data: CreateUserDto) {
    const user = await this.userRepo.save(data);
    this.eventEmitter.emit('user.created', user);
    return user;
  }
}

// orders.service.ts
@Injectable()
export class OrdersService {
  @OnEvent('user.created')
  handleUserCreated(user: User) {
    // React to user creation without direct dependency
  }
}

Reference: NestJS Circular Dependency