name: nestjs-clean-typescript
description: Clean NestJS API development with TypeScript following SOLID principles, modular architecture, and comprehensive testing practices.

NestJS Clean TypeScript

Guidelines by Alberto Basalo for developing clean NestJS APIs using TypeScript. These rules emphasize strong typing, clean code principles, and architectural best practices.

TypeScript General Principles

• Always declare the type of each variable and function (parameters and return value)
• Avoid using any; create necessary types instead
• Use JSDoc for public classes and methods
• One export per file

Naming Conventions

• PascalCase for classes
• camelCase for variables and functions
• kebab-case for files and directories
• UPPERCASE for environment variables
• Boolean variables use prefixes: isX, hasX, canX

Function Design

• Write short functions with a single purpose. Less than 20 instructions
• Use early returns to avoid nesting
• Apply RO-RO pattern: pass objects for multiple parameters, return objects for results

Data and Classes

• Prefer immutability for data with readonly and as const
• Follow SOLID principles
• Classes should have:
• Less than 200 instructions
• Fewer than 10 public methods
• Fewer than 10 properties

NestJS Specific Guidelines

• Use modular architecture with one module per domain/route
• Use MikroORM entities for persistence
• One service per entity
• DTOs validated with class-validator
• Global filters, middlewares, guards, and interceptors in core module

Testing

• Use Jest framework
• Follow Arrange-Act-Assert convention
• Write unit tests for each public function
• Include end-to-end tests per API module