Setup Pre Commit

Setup Pre-Commit Hooks

What This Sets Up

• Husky pre-commit hook
• lint-staged running Prettier on all staged files
• Prettier config (if missing)
• typecheck and test scripts in the pre-commit hook (if they exist)

Workflow

1. Detect package manager from lock file: package-lock.json (npm), pnpm-lock.yaml (pnpm), yarn.lock (yarn), bun.lockb (bun). Default to npm if unclear.

2. Install devDependencies:

   husky lint-staged prettier
   

3. Initialize Husky:

   npx husky init
   

   This creates .husky/ dir and adds prepare: "husky" to package.json.

4. Create .husky/pre-commit (no shebang needed for Husky v9+):

   npx lint-staged
   <pm> run typecheck
   <pm> run test
   

   Replace <pm> with detected package manager. If repo has no typecheck script in package.json, omit that line and tell the user. Same for test.

5. Create .lintstagedrc:

   {
     "*": "prettier --ignore-unknown --write"
   }
   

6. Create .prettierrc (only if no Prettier config exists):

   {
     "useTabs": false,
     "tabWidth": 2,
     "singleQuote": true,
     "trailingComma": "all"
   }
   

7. Verify:

   • .husky/pre-commit exists and is executable
   • .lintstagedrc exists
   • prepare script in package.json is "husky"
   • Prettier config exists
   • Run npx lint-staged to confirm it works

8. Commit all changed/created files: Add pre-commit hooks (husky + lint-staged + prettier) This runs through the new pre-commit hooks -- a good smoke test.

Rules

• Never overwrite existing Prettier config
• Never overwrite existing .husky/pre-commit without asking user first
• Always use detected package manager consistently
• Husky v9+ doesn't need shebangs in hook files
• prettier --ignore-unknown skips files Prettier can't parse (images, etc.)
• Pre-commit runs lint-staged first (fast, staged-only), then full typecheck and tests

Error Handling

• No package.json found -- report and stop
• Existing .husky/pre-commit -- ask user before overwriting
• husky init fails -- check node_modules exists, suggest running install first
• npx lint-staged verification fails -- check Prettier is installed, check .lintstagedrc syntax
• No typecheck or test scripts -- omit from hook, tell user which were skipped

See Also

• validate-code -- run lint/typecheck/tests manually
• commit -- create git commits following repo style