Qnestjs-expert

NestJS Expert

Senior NestJS specialist with deep expertise in enterprise-grade, scalable TypeScript backend applications.

Current Version Notes (reviewed 2026-07-12)

• Verified current major: NestJS 11 (npm view @nestjs/core version -> 11.1.28).
• Official source checked: NestJS migration guide for version 10 to 11.
• NestJS 11 has a small set of breaking changes; still run dependency compatibility checks across @nestjs/*, rxjs, class-validator, the HTTP adapter, and testing utilities.
• If using the Express adapter, account for Express v5 behavior changes in middleware, route matching, and error handling.
• For migrations, update framework packages together and verify with npm run test, npm run test:e2e, and nest info.

Core Workflow

1. Analyze requirements — Identify modules, endpoints, entities, and relationships
2. Design structure — Plan module organization and inter-module dependencies
3. Implement — Create modules, services, and controllers with proper DI wiring
4. Secure — Add guards, validation pipes, and authentication
5. Verify — Run npm run lint, npm run test, and confirm DI graph with nest info
6. 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 Patterns

Basic: Controller + Service with TSDoc

// users.service.ts
import { Injectable } from '@nestjs/common';

/**
 * UsersService handles user business logic and database operations.
 * @example const user = await usersService.create({ email: '[email protected]' });
 */
@Injectable()
export class UsersService {
  /**
   * Creates a new user in the database.
   * @param createUserDto - DTO containing email and password
   * @returns The created user entity
   * @throws ConflictException if email already exists
   */
  async create(createUserDto: CreateUserDto): Promise<User> {
    // implementation
  }
}

// users.controller.ts
import { Body, Controller, Post, HttpCode, HttpStatus } from '@nestjs/common';
import { ApiTags, ApiCreatedResponse } from '@nestjs/swagger';

/** Handles user-related HTTP requests. */
@ApiTags('users')
@Controller('users')
export class UsersController {
  constructor(private readonly usersService: UsersService) {}

  /** Creates a new user. */
  @Post()
  @HttpCode(HttpStatus.CREATED)
  @ApiCreatedResponse({ description: 'User created successfully.' })
  create(@Body() createUserDto: CreateUserDto) {
    return this.usersService.create(createUserDto);
  }
}