setup-butler: Instructions file for Codex

Persona

Specialize in developing GitHub Actions with clear, DRY, understandable code.

Project

• Tech Stack:
  • GitHub Actions toolkit:
    • @actions/core 3 (functions for setting results, logging, registering secrets and exporting variables across actions)
    • @actions/exec 3 (executes cross-platform tools)
    • @actions/tool-cache 4 (downloads and caches tools)
  • TypeScript 6 (strict mode)
  • @vercel/ncc 0.44 (build tool)
  • Node.js 24 (runtime used to execute the code)
• File Structure:
  • action.yml (action metadata)
  • src/ (action code)
  • dist/ (build artifact)

Commands

• Build: npm run build (compiles a Node.js module into a single file with ncc, outputs to dist/index.js)
• Lint: npm run lint:fix (auto-fixes ESLint errors)
• Type check: npm run lint:tsc (checks TypeScript for errors)
• Test: npm run test:ci (runs Vitest unit tests, must pass with 100% coverage before commits)

Standards

Follow these rules for all code you write:

Naming conventions:

• Functions: camelCase (getArch, getDownloadObject)
• Classes: PascalCase (ToolManager, Config)
• Constants: UPPER_SNAKE_CASE (CLI_NAME, CLI_VERSION)

Code style example:

// ✅ Good - descriptive names, no `any` types
function getBinaryPath(directory: string, name: string) {
  return path.join(directory, name + (os.platform() === 'win32' ? '.exe' : ''));
}

// ❌ Bad - vague names, `any` types
function getOutput(a: any, b: any) {
  return path.join(a, b + (os.platform() === 'win32' ? '.exe' : ''));
}

Boundaries:

• ✅ Always: Write to action.yml and src/, run lint, type check, and test before commits, follow naming conventions
• ⚠️ Ask first: Adding dependencies, modifying CI/CD config
• 🚫 Never: Commit secrets or API keys, edit dist/ and node_modules/