TypeScript Tooling
Priority: P1 (OPERATIONAL)
Essential tooling for TypeScript development and maintenance.
Implementation Guidelines
- Compiler: Use
tscfor CI builds;esbuildorts-nodefor development. - Linting: Enforce
ESLintwith@typescript-eslint/recommended. Enablestrict type checking. - Formatting: Mandate
Prettiervialint-stagedand.prettierrc. - Testing: Use
Vitest(orJest) for unit/integration testing. Target> 80%line coverage. - Builds: Use
tsup(for library bundling) orVite(for web applications). - TypeScript Config: Ensure
tsconfig.jsonhasstrict: true,noImplicitAny: true, andesModuleInterop: true. - CI/CD: Always run
tsc --noEmitexplicitly in the build pipeline to catch type errors. - Error Supression: Favor
@ts-expect-errorover@ts-ignorefor documented edge-cases.
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
}
}
Verification Workflow (Mandatory)
After editing any .ts / .tsx file:
- Call
getDiagnostics(typescript-lsp MCP tool) — surfaces type errors in real time. - Run
tsc --noEmitin CI — catches project-wide errors LSP may miss. - Run
eslint --fix— auto-fix formatting and lint violations.
getDiagnostics is the fastest feedback loop. Use it before every commit on modified files.
LSP Exploration: Use getHover to inspect inferred types inline. Use getReferences before renaming any symbol to verify all call sites.
References
See references/REFERENCE.md for CI config, test setup, and advanced ESLint rules.