TypeScript Tooling

TypeScript Tooling

Priority: P1 (OPERATIONAL)

Essential tooling for TypeScript development and maintenance.

Implementation Guidelines

• Compiler: tsc for CI. ts-node/esbuild for dev.
• Lint: ESLint + @typescript-eslint. Strict type checking.
• Format: Prettier (on save + commit).
• Test: Jest/Vitest > 80% coverage.
• Build: tsup (libs), Vite/Webpack (apps).
• Check: tsc --noEmit in CI.

Anti-Patterns

• No Disable: Avoid // eslint-disable.
• No Skip: Avoid skipLibCheck: true if possible.
• No Ignore: Use @ts-expect-error > @ts-ignore.

ESLint Configuration

Strict Mode Requirement

CRITICAL: Every file in the project, including tests (.spec.ts), must adhere to strict type-checked rules. NEVER turn off @typescript-eslint/no-explicit-any or no-unsafe-* rules.

Common Linting Issues & Solutions

Request Object Typing

Problem: Using any for Express request objects or creating duplicate inline interfaces. Solution: Use the centralized interfaces in src/common/interfaces/request.interface.ts.

import { RequestWithUser } from 'src/common/interfaces/request.interface';

Unused Parameters

Problem: Function parameters marked as unused by linter. Solution: Prefix the parameter with an underscore (e.g., _data) or remove it. NEVER use eslint-disable.

Test Mock Typing

Problem: Jest mocks triggering unsafe type warnings when expect.any() or custom mocks are used. Solution: Cast the mock or expectation using as unknown as TargetType.

mockRepo.save.mockResolvedValue(result as unknown as User);

Configuration

// tsconfig.json
{
  "compilerOptions": {
    "strict": true,
    "noImplicitReturns": true,
    "noUnusedLocals": true
  }
}

Reference & Examples

For testing configuration and CI/CD setup: See references/REFERENCE.md.

Related Topics

best-practices | language