setup-pre-commit

Guides a safe, repo-aware pre-commit setup. This skill is guidance-first: inspect the target repository, explain the planned changes, and only mutate dependency, hook, package, lint-staged, or Prettier files after the user approves that setup.

What this configures

• Husky v9+ with a .husky/pre-commit hook
• lint-staged running Prettier on staged files
• Prettier defaults only when no Prettier config exists
• Optional typecheck and test commands only when the target package.json already defines those scripts
• Verification commands and a real commit smoke test when the user is ready to commit setup changes

1. Preflight the target repo

Work from the target repo root, then inspect existing package and config state before proposing commands:

git status --short
node -e "const fs=require('fs'); const p=JSON.parse(fs.readFileSync('package.json','utf8')); process.stdout.write(JSON.stringify({packageManager:p.packageManager||null,scripts:p.scripts||{}}, null, 2)+'\n');"
node -e "const fs=require('fs'); const files=['bun.lock','bun.lockb','pnpm-lock.yaml','yarn.lock','package-lock.json','.lintstagedrc','.lintstagedrc.json','.lintstagedrc.js','lint-staged.config.js','.prettierrc','.prettierrc.json','.prettierrc.js','prettier.config.js','prettier.config.cjs','prettier.config.mjs']; process.stdout.write(files.filter((f)=>fs.existsSync(f)).join('\n')+'\n');"

Stop and ask before editing if the repo has unrelated dirty changes, multiple package managers, or an existing hook/config whose intent is unclear.

2. Detect the package manager

Prefer the packageManager field in package.json, then lockfiles:

Signal	Package manager
packageManager starts with bun or bun.lock / bun.lockb exists	Bun
packageManager starts with pnpm or pnpm-lock.yaml exists	pnpm
packageManager starts with yarn or yarn.lock exists	Yarn
packageManager starts with npm or package-lock.json exists	npm

If there is no clear signal, default to npm only after telling the user that no lockfile or package-manager pin was found.

3. Install dev dependencies

Use exactly one command for the detected package manager:

Package manager	Command
Bun	bun add --dev husky lint-staged prettier
pnpm	pnpm add --save-dev husky lint-staged prettier
Yarn	yarn add --dev husky lint-staged prettier --non-interactive
npm	npm install --save-dev husky lint-staged prettier --yes

Do not run these commands while porting this skill. Run them only when applying the skill to a target repo with user approval.

4. Initialize Husky

After dependencies are installed, initialize Husky with the detected package manager:

Package manager	Command
Bun	bunx --bun husky init
pnpm	pnpm exec husky init
Yarn	yarn exec husky init
npm	npx --yes husky init

Husky v9+ creates .husky/pre-commit and usually adds prepare: "husky" to package.json. Preserve an existing prepare script by combining commands only if the user approves the exact package script change.

5. Compose .husky/pre-commit

The hook must run lint-staged first, then only the package scripts that already exist. Do not add failing placeholder lines for missing scripts.

Package manager	lint-staged line	Existing typecheck script	Existing test script
Bun	bunx --bun lint-staged	bun run typecheck	bun run test
pnpm	pnpm exec lint-staged	pnpm run typecheck	pnpm run test
Yarn	yarn exec lint-staged	yarn run typecheck	yarn run test
npm	npx --no-install lint-staged	npm run typecheck	npm run test

Example for a Bun repo that has both scripts:

bunx --bun lint-staged
bun run typecheck
bun run test

If the repo lacks typecheck or test, omit that line and tell the user which check was skipped.

6. Configure lint-staged and Prettier

Respect existing config:

1. If a lint-staged config already exists, update it only after confirming it should run Prettier on staged files.
2. If no lint-staged config exists, add one config location that matches repo style. Prefer an existing package.json config style if the repo already keeps tool config there; otherwise use .lintstagedrc.json.
3. Use this minimal lint-staged config:

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

4. If any Prettier config exists, do not overwrite it.
5. If no Prettier config exists, propose these defaults:

{
  "useTabs": false,
  "tabWidth": 2,
  "printWidth": 80,
  "singleQuote": false,
  "trailingComma": "es5",
  "semi": true,
  "arrowParens": "always"
}

prettier --ignore-unknown lets staged binary or unsupported files pass without parse failures.

7. Verify

Run only commands that match the detected package manager and existing scripts:

git status --short

• Confirm .husky/pre-commit exists and contains the selected lint-staged line.
• Confirm package.json has a valid Husky prepare script without clobbering previous behavior.
• Confirm lint-staged config exists and Prettier config is preserved or created intentionally.
• Run the selected lint-staged command with staged setup files.
• Run the selected typecheck/test commands only if those scripts exist.

8. Smoke test with a real commit

When the user is ready to commit the setup, use the normal commit as the smoke test:

git add package.json .husky/pre-commit .lintstagedrc.json .prettierrc
git commit -m "chore: add pre-commit checks"

Adjust the git add paths to the files actually changed. Do not create an empty or throwaway commit just to test the hook, and do not run a commit smoke test unless the user explicitly wants the setup committed.