setup-pre-commit

Setup Pre-Commit Hooks

Set up a repo-appropriate Husky pre-commit hook using the existing package manager and scripts. Prefer the smallest change that fits the repo.

What This Sets Up

• Husky pre-commit hook.
• lint-staged running Prettier on staged files.
• Prettier config only if the repo does not already have one.
• Existing typecheck/check and test scripts in the pre-commit hook when available.

Process

1. Inspect The Repo

Read package.json and check for lockfiles:

• package-lock.json - npm.
• pnpm-lock.yaml - pnpm.
• yarn.lock - yarn.
• bun.lock or bun.lockb - bun.

Use the package manager already used by the repo. Default to npm only if unclear.

Check existing scripts before writing the hook. Prefer, in order:

• Type checking: typecheck, check.
• Tests: test, test:unit.
• Formatting: format, otherwise lint-staged with Prettier.

2. Install Dependencies

Install these as dev dependencies using the detected package manager:

husky lint-staged prettier

Skip dependencies already present.

3. Initialize Husky

Use the package-manager equivalent of Husky init. For npm:

npx husky init

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

4. Write .husky/pre-commit

Use the detected package manager's runner. Example for npm:

npx lint-staged
npm run typecheck
npm run test

Adapt the script names to what actually exists in package.json. If the repo has no typecheck/check or test script, omit that line and mention it in the final response.

Husky v9+ hook files do not need a shebang.

5. Configure Lint-Staged

Create .lintstagedrc only if no lint-staged config already exists:

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

If a lint-staged config already exists, preserve it and make the smallest needed edit.

6. Configure Prettier

Create .prettierrc only if no Prettier config exists. Use these defaults:

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

If the repo already has a Prettier config, do not replace it.

7. Verify

Verify the setup before finishing:

• .husky/pre-commit exists and is executable.
• prepare script in package.json is present.
• lint-staged config exists.
• Prettier config exists or the repo intentionally relies on defaults.
• Run the package-manager equivalent of lint-staged if feasible.

Rules

• Do not create a commit unless the user explicitly asks.
• Do not overwrite an existing formatting, lint-staged, or hook setup.
• If the hook would be too slow because the repo has expensive tests, ask before adding the full test command.
• Keep the final response factual: files changed, scripts added, and verification run.