nestjs-expert

name	nestjs-expert
type	reference
description	Provides NestJS patterns for modules, controllers, providers, guards, interceptors, and microservices. Use when working with NestJS TypeScript files (*.module.ts, *.controller.ts, *.service.ts) or when the user mentions NestJS, Nest.js, or NestJS modules.
paths	["**/*.module.ts","**/*.controller.ts","**/*.service.ts","**/*.guard.ts","**/nest-cli.json"]
effort	3
allowed-tools	Read, Glob, Grep, Write, Edit, Bash
user-invocable	true
when_to_use	When building NestJS backend APIs, microservices, or guards/interceptors

NestJS Expert

Critical rules (non-obvious)

• Circular dependencies: use forwardRef(() => ServiceB) in both modules; better — restructure to avoid
• Global modules: use @Global() sparingly; prefer explicit imports to keep modules testable
• APP_GUARD / APP_INTERCEPTOR: registered in AppModule providers, not in individual modules
• Lifecycle hooks order: onModuleInit → onApplicationBootstrap → ready; onModuleDestroy → beforeApplicationShutdown → onApplicationShutdown
• Never use req.user without type assertion — it's any from Passport; extend Express.Request

Module structure

@Module({
  imports: [TypeOrmModule.forFeature([User]), JwtModule],
  controllers: [UserController],
  providers: [UserService, UserRepository],
  exports: [UserService],   // export what other modules need
})
export class UserModule {}

Controller with validation

@Controller("users")
@UseGuards(JwtAuthGuard)
export class UserController {
  constructor(private readonly userService: ) {}

  ()
  (.)
   () {
     ..(id);
  }

  ()
  (.)
   () {
     ..(dto);
  }
}