pre-commit-linting
PreToolUseAutomatically run linters before committing code to catch issues early.
Features
Installation
1. Copy hook to your project
Terminal
cp -r hooks/pre-commit-linting/ /your-project/.claude/hooks/pre-commit-linting/2. Add to settings.json
.claude/settings.json
{
"hooks": {
"PreToolUse": [{
"matcher": "Bash",
"hooks": [{
"type": "command",
"command": "$CLAUDE_PROJECT_DIR/.claude/hooks/pre-commit-linting/hook.sh"
}]
}]
}
}3. Make executable
Terminal
chmod +x .claude/hooks/pre-commit-linting/hook.shAutomatically run linters before committing code to catch issues early.
Hook Configuration
Add to your .claude/settings.json:
{
"hooks": {
"PreToolUse": [
{
"matcher": "Bash",
"hooks": [
{
"type": "command",
"command": "$CLAUDE_PROJECT_DIR/.claude/hooks/pre-commit-linting/check.sh",
"timeout": 30
}
]
}
]
}
}
Hook Script
Save as .claude/hooks/pre-commit-linting/check.sh:
#!/bin/bash
set -euo pipefail
# Parse hook input
INPUT=$(cat)
TOOL_INPUT=$(echo "$INPUT" | jq -r '.tool_input.command // empty')
# Only check git commit commands
if [[ ! "$TOOL_INPUT" =~ git[[:space:]]+commit ]]; then
echo '{"continue": true, "suppressOutput": true}'
exit 0
fi
# Run linters
echo "Running pre-commit linters..." >&2
ERRORS=()
# ESLint for JavaScript/TypeScript
if command -v eslint &> /dev/null && [ -f .eslintrc.json ] || [ -f .eslintrc.js ]; then
if ! eslint . --max-warnings 0 2>&1; then
ERRORS+=("ESLint found issues")
fi
fi
# Prettier for formatting
if command -v prettier &> /dev/null && [ -f .prettierrc ]; then
if ! prettier --check . 2>&1; then
ERRORS+=("Prettier formatting issues found")
fi
fi
# Pylint for Python
if command -v pylint &> /dev/null && find . -name "*.py" -not -path "./venv/*" | head -1 | grep -q .; then
if ! pylint **/*.py --fail-under=8.0 2>&1; then
ERRORS+=("Pylint found issues")
fi
fi
# RuboCop for Ruby
if command -v rubocop &> /dev/null && [ -f .rubocop.yml ]; then
if ! rubocop 2>&1; then
ERRORS+=("RuboCop found issues")
fi
fi
# Report results
if [ ${#ERRORS[@]} -gt 0 ]; then
ERROR_MSG="Pre-commit linting failed:\\n"
for error in "${ERRORS[@]}"; do
ERROR_MSG+=" - $error\\n"
done
ERROR_MSG+="\\nPlease fix these issues before committing."
echo "{\"permissionDecision\": \"deny\", \"reason\": \"$ERROR_MSG\"}" | jq -c
exit 2
fi
echo '{"permissionDecision": "allow"}'
exit 0
Setup
- Make the script executable:
chmod +x .claude/hooks/pre-commit-linting/check.sh - Install linters for your stack:
JavaScript/TypeScript:
npm install --save-dev eslint prettier
npx eslint --init
Python:
pip install pylint black
Ruby:
gem install rubocop
- Configure each linter with project-specific rules
Features
- ✅ Automatically runs before git commits
- ✅ Checks multiple file types (JS, TS, Python, Ruby)
- ✅ Blocks commits with linting errors
- ✅ Fast execution with 30-second timeout
- ✅ Provides clear error messages
- ✅ Skips non-commit Bash commands
Customization
Add more linters by extending the script:
# Go
if command -v golangci-lint &> /dev/null && [ -f go.mod ]; then
if ! golangci-lint run 2>&1; then
ERRORS+=("golangci-lint found issues")
fi
fi
# Rust
if command -v cargo &> /dev/null && [ -f Cargo.toml ]; then
if ! cargo clippy -- -D warnings 2>&1; then
ERRORS+=("Clippy found issues")
fi
fi
Bypassing (When Necessary)
For emergency commits, you can temporarily disable:
# Commit without hooks
git commit --no-verify -m "Emergency fix"
Best Practices
- Keep linting rules consistent across team
- Run linters in CI/CD as well
- Auto-fix when possible (prettier –write)
- Configure IDE integration for real-time feedback
- Use .gitignore patterns to exclude generated files