TypeScript Tooling

Priority: P1 (OPERATIONAL)

Implementation Guidelines

• Compiler: Use tsc for CI builds; esbuild or ts-node for development.
• Linting: Enforce ESLint with @typescript-eslint/recommended. Enable strict type checking.
• Formatting: Mandate Prettier via lint-staged and .prettierrc.
• Testing: Use Vitest (or Jest) for unit/integration testing. Target > 80% line coverage.
• Builds: Use tsup (library bundling) or Vite (web applications).
• TypeScript Config: Aim for strict: true long-term. For existing projects, migrate incrementally: start with strictNullChecks, then noImplicitAny, strictFunctionTypes. Do NOT flip strict: true in one step.
• CI/CD: Always run tsc --noEmit in build pipeline to catch type errors.
• Error Suppression: Favor @ts-expect-error over @ts-ignore for documented edge-cases.

ESLint Configuration

Enable @typescript-eslint/recommended at minimum. When strict: false in tsconfig, no-unsafe-* rules may produce excessive noise — suppress selectively with @ts-expect-error rather than disabling globally.

See reference for common linting issues (request typing, unused params, test mock typing) and tsconfig migration examples.

Verification Workflow (Mandatory)

After editing any .ts / .tsx file:

1. Call getDiagnostics (typescript-lsp MCP tool) — surfaces type errors in real time.
2. Run tsc --noEmit in CI — catches project-wide errors LSP may miss.
3. Run eslint --fix — auto-fix formatting and lint violations.

Fallback when typescript-lsp MCP unconfigured: run tsc --noEmit directly.

getDiagnostics fastest feedback loop. Use it before every commit on modified files. Use getHover to inspect inferred types, getReferences before renaming symbols.

Anti-Patterns

• No @ts-ignore: Use @ts-expect-error — self-documents intent, fails if error disappears.
• No any for request objects: Import centralized interfaces from src/common/interfaces/.
• No eslint-disable (global): Suppress per-line; fix root cause instead.
• No atomic strict: true flip on existing repos: migrate incrementally starting with strictNullChecks.

References

• Config Examples & Linting Patterns