Setup Pre-commit Hooks

Overview

Configure comprehensive pre-commit hooks to catch issues before they reach the repository. Quality gates that run automatically on every commit.

Core principle: Catch problems early. Every commit should be deployable.

Trigger: /setup-precommit command

What Gets Configured

For JavaScript/TypeScript Projects

.husky/pre-commit:

#!/usr/bin/env sh
. "$(dirname -- "$0")/_/husky.sh"

# Run type check
npx tsc --noEmit

# Run lint on staged files
npx lint-staged

# Run affected tests
npx jest --onlyChanged --passWithNoTests

.lintstagedrc.json:

{
  "*.{ts,tsx}": [
    "eslint --fix",
    "prettier --write"
  ],
  "*.{json,md}": [
    "prettier --write"
  ]
}

.husky/commit-msg:

#!/usr/bin/env sh
. "$(dirname -- "$0")/_/husky.sh"

npx --no -- commitlint --edit "$1"

commitlint.config.js:

module.exports = {
  extends: ['@commitlint/config-conventional'],
  rules: {
    'type-enum': [2, 'always', [
      'feat', 'fix', 'docs', 'style', 'refactor',
      'perf', 'test', 'chore', 'revert', 'ci'
    ]],
    'subject-case': [2, 'always', 'lower-case'],
    'header-max-length': [2, 'always', 72]
  }
};

For Python Projects

.pre-commit-config.yaml:

repos:
  - repo: https://github.com/pre-commit/pre-commit-hooks
    rev: v4.5.0
    hooks:
      - id: trailing-whitespace
      - id: end-of-file-fixer
      - id: check-yaml
      - id: check-added-large-files

  - repo: https://github.com/astral-sh/ruff-pre-commit
    rev: v0.1.9
    hooks:
      - id: ruff
        args: [--fix]
      - id: ruff-format

  - repo: https://github.com/pre-commit/mirrors-mypy
    rev: v1.8.0
    hooks:
      - id: mypy
        additional_dependencies: [types-all]

  - repo: local
    hooks:
      - id: pytest
        name: pytest
        entry: pytest
        language: system
        pass_filenames: false
        always_run: true

Setup Process

Step 1: Detect Project Type

if [ -f "package.json" ]; then
  PROJECT_TYPE="node"
elif [ -f "pyproject.toml" ] || [ -f "requirements.txt" ]; then
  PROJECT_TYPE="python"
elif [ -f "Cargo.toml" ]; then
  PROJECT_TYPE="rust"
else
  PROJECT_TYPE="generic"
fi

Step 2: Install Dependencies

Node.js:

npm install -D husky lint-staged @commitlint/cli @commitlint/config-conventional
npx husky init

Python:

pip install pre-commit
pre-commit install

Rust:

cargo install cargo-husky

Step 3: Create Hook Files

Generate appropriate hook files based on project type.

Step 4: Verify Installation

# Test pre-commit hook
echo "test" > test-file.txt
git add test-file.txt
git commit -m "test: verify pre-commit hooks" --dry-run

# Clean up
rm test-file.txt

Step 5: Configure CI Integration

Add to CI workflow to run same checks:

.github/workflows/quality.yml:

name: Quality Checks

on:
  push:
    branches: [main]
  pull_request:
    branches: [main]

jobs:
  quality:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - name: Setup Node.js
        uses: actions/setup-node@v4
        with:
          node-version: '20'
          cache: 'npm'

      - name: Install dependencies
        run: npm ci

      - name: Type check
        run: npx tsc --noEmit

      - name: Lint
        run: npm run lint

      - name: Test
        run: npm test

Quality Gate Levels

Level 1: Basic (Default)

• Trailing whitespace
• End of file newline
• Check YAML/JSON syntax
• Large file warning

Level 2: Standard

• Level 1 +
• Lint with auto-fix
• Format code
• Type checking

Level 3: Strict

• Level 2 +
• Run tests
• Check test coverage
• Commit message validation

Level 4: Enterprise

• Level 3 +
• Security scanning
• License compliance
• Dependency audit

Post-Setup

Pre-commit hooks configured!

Hooks installed:
- pre-commit: Type check, lint, format, test
- commit-msg: Conventional commit validation

Quality level: [Standard]

Commands:
- Skip hooks once: git commit --no-verify
- Run manually: npx lint-staged
- Bypass specific: HUSKY=0 git commit

Would you like to:
1. Test the hooks with a sample commit
2. Upgrade to Strict quality level
3. Configure CI to match

Troubleshooting

Hook Not Running

# Check husky installation
ls .husky/

# Reinstall hooks
npx husky install

# Make executable (Unix)
chmod +x .husky/*

Too Slow

• Use lint-staged to only check changed files
• Configure test runner to only run affected tests
• Cache TypeScript compilation

Bypassing When Needed

# Skip all hooks
git commit --no-verify -m "emergency fix"

# Skip specific hooks (set in hook script)
SKIP=eslint git commit -m "fix: bypass lint"

Integration

Requires:

• Project analysis (detects appropriate hooks)

Enables:

• Consistent code quality
• Automatic formatting
• Early bug detection
• Standardized commits