jeffallan/nestjs-expert
Creates and configures NestJS modules, controllers, services, DTOs, guards, and interceptors for enterprise-grade TypeScript backend applications. Use when building NestJS REST APIs or GraphQL services, implementing dependency injection, scaffolding modular architecture, adding JWT/Passport authentication, integrating TypeORM or Prisma, or working with .module.ts, .controller.ts, and .service.ts files. Invoke for guards, interceptors, pipes, validation, Swagger documentation, and unit/E2E testing in NestJS projects.
npx skills add https://github.com/Jeffallan/claude-skills --skill nestjs-expertSenior NestJS specialist with deep expertise in enterprise-grade, scalable TypeScript backend applications.
npm run lint, npm run test, and confirm DI graph with nest infoLoad 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 |
// create-user.dto.ts
import { IsEmail, IsString, MinLength } from 'class-validator';
import { ApiProperty } from '@nestjs/swagger';
export class CreateUserDto {
@ApiProperty({ example: '[email protected]' })
@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);
}
}
// 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;
}
}
// 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 {}
// 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: '[email protected]' });
await expect(
service.create({ email: '[email protected]', password: 'pass1234' }),
).rejects.toThrow(ConflictException);
});
});
@Injectable() and constructor injection for all services — never instantiate services with newclass-validator decorators on DTOs and enable ValidationPipe globallyreq.body to servicesNotFoundException, ConflictException, etc.) in services@ApiTags, @ApiOperation, and response decoratorsTest.createTestingModuleConfigModule and process.env; never hardcode themValidationPipeany type unless absolutely necessary and documentedforwardRef() only as a last resortWhen implementing a NestJS feature, provide in this order:
.module.ts).controller.ts).service.ts)class-validator decorators (dto/*.dto.ts)*.service.spec.ts)NestJS, TypeScript, TypeORM, Prisma, Passport, JWT, class-validator, class-transformer, Swagger/OpenAPI, Jest, Supertest, Guards, Interceptors, Pipes, Filters
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