Code Quality — Skill

Purpose

Maintain consistent, spec-compliant code throughout the serverless function runtime implementation.

When to Use

• Writing new source files
• Reviewing or refactoring existing code
• Making implementation decisions about structure or patterns

Language and Runtime Conventions

1. Node.js with modern JavaScript or TypeScript. Use ES modules (import/export).
2. Web-standard Request/Response for the handler contract. Use the global Request and Response objects (Node.js 18+ built-in) or a minimal polyfill.
3. Minimal dependencies. Do not add frameworks or libraries unless strictly required by the spec. Prefer Node.js built-ins.
4. No TypeScript compilation complexity. If using TypeScript, keep the build step simple. Plain JavaScript is acceptable.

Code Structure Conventions

1. One module, one responsibility. Each file should have a clear, single purpose.
2. Named exports for public API. Default exports only for handler method functions.
3. Handler functions are named by HTTP method: export function GET(request) {}, export function POST(request) {}.
4. No global mutable state except where explicitly required by the spec (warm module reuse via module-level variables is allowed per REQ-RTG-006).

Error Handling Conventions

1. Runtime errors use the spec's JSON format: {"errorCode": "<CODE>", "message": "<detail>"}.
2. Error codes are exactly: ROUTE_NOT_FOUND, METHOD_NOT_ALLOWED, HANDLER_EXCEPTION, INVALID_HANDLER_RESPONSE, INVOCATION_TIMEOUT.
3. HTTP status mapping is fixed: 404, 405, 500, 500, 504 respectively.
4. Handler exceptions must be caught and mapped to HANDLER_EXCEPTION with the original error message.
5. Timeout enforcement uses AbortController or equivalent — do not rely on unref'd timers alone.

Testing Conventions

1. E2E tests run via npm test (REQ-RCV-006).
2. Tests start the runtime, send HTTP requests, and assert responses. No mocking of the runtime itself.
3. Each spec scenario (Section 6) maps to at least one test case.
4. Test exit code 0 on success (REQ-RCV-007).

Quality Checklist

• All source files use ES modules
• Handler contract uses Web-standard Request/Response
• No unnecessary dependencies added
• Error responses match spec JSON format exactly
• Timeout enforcement is 3000ms per invocation
• No debug prints or commented-out code in committed files
• Each file has a single, clear responsibility