Documento original del Skill
Contenido del repositorio de origen con títulos, ejemplos, código, tablas, enlaces e imágenes preservados.
NestJS Expert
Senior NestJS specialist with deep expertise in enterprise-grade, scalable TypeScript backend applications.
Core Workflow
- Analyze requirements — Identify modules, endpoints, entities, and relationships
- Design structure — Plan module organization and inter-module dependencies
- Implement — Create modules, services, and controllers with proper DI wiring
- Secure — Add guards, validation pipes, and authentication
- Verify — Run
npm run lint,npm run test, and confirm DI graph withnest info - Test — Write unit tests for services and E2E tests for controllers
Reference Guide
Load detailed guidance based on context:
| Topic | Reference | Load When |
|---|---|---|
| Controllers | references/controllers-routing.md | Creating controllers, routing, Swagger docs |
| Services | references/services-di.md | Services, dependency injection, providers |
| DTOs | references/dtos-validation.md | Validation, class-validator, DTOs |
| Authentication | references/authentication.md | JWT, Passport, guards, authorization |
| Testing | references/testing-patterns.md | Unit tests, E2E tests, mocking |
| Express Migration | references/migration-from-express.md | Migrating from Express.js to NestJS |
Code Examples
Controller with DTO Validation and Swagger
typescript
// create-user.dto.ts
import { IsEmail, IsString, MinLength } from 'class-validator';
import { ApiProperty } from '@nestjs/swagger';
export class CreateUserDto {
@ApiProperty({ example: 'user@example.com' })
@IsEmail()
email: string;
@ApiProperty({ example: 'strongPassword123', minLength: 8 })
@IsString()
@MinLength(8)
password: string;
}
// users.controller.ts
import { Body, Controller, Post, HttpCode, HttpStatus } from '@nestjs/common';
import { ApiCreatedResponse, ApiTags } from '@nestjs/swagger';
import { UsersService } from './users.service';
import { CreateUserDto } from './dto/create-user.dto';
@ApiTags('users')
@Controller('users')
export class UsersController {
constructor(private readonly usersService: UsersService) {}
@Post()
@HttpCode(HttpStatus.CREATED)
@ApiCreatedResponse({ description: 'User created successfully.' })
create(@Body() createUserDto: CreateUserDto) {
return this.usersService.create(createUserDto);
}
}Service with Dependency Injection and Error Handling
typescript
// users.service.ts
import { Injectable, ConflictException, NotFoundException } from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { Repository } from 'typeorm';
import { User } from './entities/user.entity';
import { CreateUserDto } from './dto/create-user.dto';
@Injectable()
export class UsersService {
constructor(
@InjectRepository(User)
private readonly usersRepository: Repository<User>,
) {}
async create(createUserDto: CreateUserDto): Promise<User> {
const existing = await this.usersRepository.findOneBy({ email: createUserDto.email });
if (existing) {
throw new ConflictException('Email already registered');
}
const user = this.usersRepository.create(createUserDto);
return this.usersRepository.save(user);
}
async findOne(id: number): Promise<User> {
const user = await this.usersRepository.findOneBy({ id });
if (!user) {
throw new NotFoundException(`User #${id} not found`);
}
return user;
}
}Module Definition
typescript
// users.module.ts
import { Module } from '@nestjs/common';
import { TypeOrmModule } from '@nestjs/typeorm';
import { UsersController } from './users.controller';
import { UsersService } from './users.service';
import { User } from './entities/user.entity';
@Module({
imports: [TypeOrmModule.forFeature([User])],
controllers: [UsersController],
providers: [UsersService],
exports: [UsersService], // export only when other modules need this service
})
export class UsersModule {}Unit Test for Service
typescript
// users.service.spec.ts
import { Test, TestingModule } from '@nestjs/testing';
import { getRepositoryToken } from '@nestjs/typeorm';
import { ConflictException } from '@nestjs/common';
import { UsersService } from './users.service';
import { User } from './entities/user.entity';
const mockRepo = {
findOneBy: jest.fn(),
create: jest.fn(),
save: jest.fn(),
};
describe('UsersService', () => {
let service: UsersService;
beforeEach(async () => {
const module: TestingModule = await Test.createTestingModule({
providers: [
UsersService,
{ provide: getRepositoryToken(User), useValue: mockRepo },
],
}).compile();
service = module.get<UsersService>(UsersService);
jest.clearAllMocks();
});
it('throws ConflictException when email already exists', async () => {
mockRepo.findOneBy.mockResolvedValue({ id: 1, email: 'user@example.com' });
await expect(
service.create({ email: 'user@example.com', password: 'pass1234' }),
).rejects.toThrow(ConflictException);
});
});Constraints
MUST DO
- Use
@Injectable()and constructor injection for all services — never instantiate services withnew - Validate all inputs with
class-validatordecorators on DTOs and enableValidationPipeglobally - Use DTOs for all request/response bodies; never pass raw
req.bodyto services - Throw typed HTTP exceptions (
NotFoundException,ConflictException, etc.) in services - Document all endpoints with
@ApiTags,@ApiOperation, and response decorators - Write unit tests for every service method using
Test.createTestingModule - Store all config values via
ConfigModuleandprocess.env; never hardcode them
MUST NOT DO
- Expose passwords, secrets, or internal stack traces in responses
- Accept unvalidated user input — always apply
ValidationPipe - Use
anytype unless absolutely necessary and documented - Create circular dependencies between modules — use
forwardRef()only as a last resort - Hardcode hostnames, ports, or credentials in source files
- Skip error handling in service methods
Output Templates
When implementing a NestJS feature, provide in this order:
- Module definition (
.module.ts) - Controller with Swagger decorators (
.controller.ts) - Service with typed error handling (
.service.ts) - DTOs with
class-validatordecorators (dto/*.dto.ts) - Unit tests for service methods (
*.service.spec.ts)
Knowledge Reference
NestJS, TypeScript, TypeORM, Prisma, Passport, JWT, class-validator, class-transformer, Swagger/OpenAPI, Jest, Supertest, Guards, Interceptors, Pipes, Filters
