Precommit Setup

Table of Contents

• Use When
• Philosophy: Three-Layer Defense
• Standard Hooks (Layer 1)
• Python Projects
• Basic Quality Checks
• Configuration
• Rust Projects
• TypeScript Projects
• Component-Specific Checks (Layer 2)
• Python Monorepo/Plugin Architecture
• 1. Lint Changed Components (scripts/run-component-lint.sh)
• 2. Type Check Changed Components (scripts/run-component-typecheck.sh)
• 3. Test Changed Components (scripts/run-component-tests.sh)
• Add to Pre-commit Configuration
• Validation Hooks (Layer 3)
• Example: Plugin Structure Validation
• Workflow
• 1. Create Configuration Files
• 2. Configure Python Type Checking
• 3. Configure Testing
• 4. Install and Test Hooks
• 5. Create Manual Quality Scripts
• scripts/check-all-quality.sh
• Hook Execution Order
• Performance Optimization
• Typical Timings
• Optimization Strategies
• Hook Configuration
• Skip Specific Hooks
• Custom Hooks
• CI Integration
• Troubleshooting
• Hooks Too Slow
• Cache Issues
• Hook Failures
• Import Errors in Tests
• Type Checking Errors
• Best Practices
• For New Projects
• For Existing Projects
• For Monorepos/Plugin Architectures
• Complete Example: Python Monorepo
• Related Skills
• See Also

Pre-commit Setup Skill

Configure a detailed three-layer pre-commit quality system that enforces linting, type checking, and testing before commits.

Use When

• Setting up new project with code quality enforcement
• Adding pre-commit hooks to existing project
• Upgrading from basic linting to a full quality system
• Setting up monorepo/plugin architecture with per-component quality checks
• Updating pre-commit hook versions

Philosophy: Three-Layer Defense

This skill implements a technical quality system based on three distinct layers. Layer 1 consists of fast global checks that perform quick linting and type checking on all files in approximately 50 to 200 milliseconds. Layer 2 focuses on component-specific checks, running detailed linting, type checking, and testing for changed components only, which typically takes between 10 and 30 seconds. Finally, Layer 3 uses validation hooks for structure verification, security scanning, and custom project checks. This multi-layered approach verifies that new code is automatically checked before commit, which prevents technical debt from entering the repository.

Standard Hooks (Layer 1)

Python Projects

Basic Quality Checks

1. pre-commit-hooks - File validation (trailing whitespace, EOF, YAML/TOML/JSON syntax)
2. ruff - Ultra-fast linting and formatting (~50ms)
3. ruff-format - Code formatting
4. mypy - Static type checking (~200ms)
5. bandit - Security scanning

Configuration

```yaml

.pre-commit-config.yaml

repos:

• repo: https://github.com/pre-commit/pre-commit-hooks rev: v6.0.0 hooks:

  • id: trailing-whitespace
  • id: end-of-file-fixer
  • id: check-yaml
  • id: check-toml
  • id: check-json

• repo: https://github.com/astral-sh/ruff-pre-commit rev: v0.14.2 hooks:

  • id: ruff args: [--fix]
  • id: ruff-format

• repo: https://github.com/pre-commit/mirrors-mypy rev: v1.13.0 hooks:

  • id: mypy args: [--ignore-missing-imports]

• repo: https://github.com/PyCQA/bandit rev: 1.8.0 hooks:

  • id: bandit args: [-c, pyproject.toml]

```

Rust Projects

1. rustfmt - Code formatting
2. clippy - Linting
3. cargo-check - Compilation check

TypeScript Projects

1. eslint - Linting
2. prettier - Code formatting
3. tsc - Type checking

Component-Specific Checks (Layer 2)

For monorepos, plugin architectures, or projects with multiple components, add per-component quality checks.

Python Monorepo/Plugin Architecture

Create quality check scripts:

1. Lint Changed Components (scripts/run-component-lint.sh)

```bash #!/bin/bash

Lint only changed components based on staged files

set -euo pipefail

Detect changed components from staged files

CHANGED_COMPONENTS=$(git diff --cached --name-only | grep -E '^(plugins|components)/' | cut -d/ -f2 | sort -u) || true

if [ -z "$CHANGED_COMPONENTS" ]; then echo "No components changed" exit 0 fi

echo "Linting changed components: $CHANGED_COMPONENTS"

FAILED=()

for component in $CHANGED_COMPONENTS; do if [ -d "plugins/$component" ]; then echo "Linting $component..." # Capture exit code to properly propagate failures local exit_code=0 if [ -f "plugins/$component/Makefile" ] && grep -q "^lint:" "plugins/$component/Makefile"; then (cd "plugins/$component" && make lint) || exit_code=$? else (cd "plugins/$component" && uv run ruff check .) || exit_code=$? fi if [ "$exit_code" -ne 0 ]; then FAILED+=("$component") fi fi done

if [ ${#FAILED[@]} -gt 0 ]; then echo "Lint failed for: ${FAILED[*]}" exit 1 fi ```

2. Type Check Changed Components (scripts/run-component-typecheck.sh)

```bash #!/bin/bash

Type check only changed components

set -euo pipefail

CHANGED_COMPONENTS=$(git diff --cached --name-only | grep -E '^(plugins|components)/' | cut -d/ -f2 | sort -u) || true

if [ -z "$CHANGED_COMPONENTS" ]; then exit 0 fi

echo "Type checking changed components: $CHANGED_COMPONENTS"

FAILED=()

for component in $CHANGED_COMPONENTS; do if [ -d "plugins/$component" ]; then echo "Type checking $component..." # Capture output and exit code separately to properly propagate failures local output local exit_code=0 if [ -f "plugins/$component/Makefile" ] && grep -q "^typecheck:" "plugins/$component/Makefile"; then output=$(cd "plugins/$component" && make typecheck 2>&1) || exit_code=$? else output=$(cd "plugins/$component" && uv run mypy src/ 2>&1) || exit_code=$? fi # Display output (filter make noise) echo "$output" | grep -v "^make[" || true if [ "$exit_code" -ne 0 ]; then FAILED+=("$component") fi fi done

if [ ${#FAILED[@]} -gt 0 ]; then echo "Type check failed for: ${FAILED[*]}" exit 1 fi ```

3. Test Changed Components (scripts/run-component-tests.sh)

```bash #!/bin/bash

Test only changed components

set -euo pipefail

CHANGED_COMPONENTS=$(git diff --cached --name-only | grep -E '^(plugins|components)/' | cut -d/ -f2 | sort -u) || true

if [ -z "$CHANGED_COMPONENTS" ]; then exit 0 fi

echo "Testing changed components: $CHANGED_COMPONENTS"

FAILED=()

for component in $CHANGED_COMPONENTS; do if [ -d "plugins/$component" ]; then echo "Testing $component..." # Capture exit code to properly propagate failures local exit_code=0 if [ -f "plugins/$component/Makefile" ] && grep -q "^test:" "plugins/$component/Makefile"; then (cd "plugins/$component" && make test) || exit_code=$? else (cd "plugins/$component" && uv run pytest tests/) || exit_code=$? fi if [ "$exit_code" -ne 0 ]; then FAILED+=("$component") fi fi done

if [ ${#FAILED[@]} -gt 0 ]; then echo "Tests failed for: ${FAILED[*]}" exit 1 fi ```

Add to Pre-commit Configuration

```yaml

.pre-commit-config.yaml (continued)

Layer 2: Component-Specific Quality Checks

• repo: local hooks:

  • id: run-component-lint name: Lint Changed Components entry: ./scripts/run-component-lint.sh language: system pass_filenames: false files: ^(plugins|components)/.*\.py$

  • id: run-component-typecheck name: Type Check Changed Components entry: ./scripts/run-component-typecheck.sh language: system pass_filenames: false files: ^(plugins|components)/.*\.py$

  • id: run-component-tests name: Test Changed Components entry: ./scripts/run-component-tests.sh language: system pass_filenames: false files: ^(plugins|components)/.*\.(py|md)$

```

Validation Hooks (Layer 3)

Add custom validation hooks for project-specific requirements.

Example: Plugin Structure Validation

```yaml

Layer 3: Validation Hooks

• repo: local hooks:
  • id: validate-plugin-structure name: Validate Plugin Structure entry: python3 scripts/validate_plugins.py language: system pass_filenames: false files: ^plugins/.*$

```

Workflow

1. Create Configuration Files

```bash

Create .pre-commit-config.yaml

python3 plugins/attune/scripts/attune_init.py \ --lang python \ --name my-project \ --path .

Create quality check scripts (for monorepos)

mkdir -p scripts chmod +x scripts/run-component-*.sh ```

2. Configure Python Type Checking

Create pyproject.toml with strict type checking:

```toml [tool.mypy] python_version = "3.12" warn_return_any = true warn_unused_configs = true disallow_untyped_defs = true strict = true

Per-component configuration

[[tool.mypy.overrides]] module = "plugins.*" strict = true ```

3. Configure Testing

```toml [tool.pytest.ini_options] testpaths = ["tests"] pythonpath = ["src"] addopts = [ "-v", # Verbose output "--strict-markers", # Strict marker enforcement "--cov=src", # Coverage for src/ "--cov-report=term", # Terminal coverage report ]

markers = [ "slow: marks tests as slow (deselect with '-m \"not slow\"')", "integration: marks tests as integration tests", ] ```

4. Install and Test Hooks

```bash

Install pre-commit tool

uv sync --extra dev

Install git hooks

uv run pre-commit install

Test on all files (first time)

uv run pre-commit run --all-files

Normal usage - test on staged files

git add . git commit -m "feat: add feature"

Hooks run automatically

```

5. Create Manual Quality Scripts

For full quality checks (CI/CD, monthly audits):

scripts/check-all-quality.sh

```bash #!/bin/bash

Full quality check for all components

set -e

echo "=== Running Full Quality Checks ==="

Lint all components

./scripts/run-component-lint.sh --all

Type check all components

./scripts/run-component-typecheck.sh --all

Test all components

./scripts/run-component-tests.sh --all

echo "=== All Quality Checks Passed ===" ```

Hook Execution Order

Pre-commit hooks run in this order:

```

1. File Validation (whitespace, EOF, YAML/TOML/JSON syntax)
2. Security Scanning (bandit)
3. Global Linting (ruff - all files)
4. Global Type Checking (mypy - all files)
5. Component Linting (changed components only)
6. Component Type Checking (changed components only)
7. Component Tests (changed components only)
8. Custom Validation (structure, patterns, etc.) ```

All must pass for commit to succeed.

Performance Optimization

Typical Timings

Optimization Strategies

1. Only test changed components - Default behavior
2. Parallel execution - Hooks run concurrently when possible
3. Caching - Dependencies cached by uv
4. Incremental mypy - Use --incremental flag

Hook Configuration

Skip Specific Hooks

```bash

Skip specific hook for one commit

SKIP=run-component-tests git commit -m "WIP: tests in progress"

Skip component checks but keep global checks

SKIP=run-component-lint,run-component-typecheck,run-component-tests git commit -m "WIP"

Skip all hooks (DANGEROUS - use only for emergencies)

git commit --no-verify -m "Emergency fix" ```

Custom Hooks

Add project-specific hooks:

```yaml

• repo: local hooks:

  • id: check-architecture name: Validate Architecture Decisions entry: python3 scripts/check_architecture.py language: system pass_filenames: false files: ^(plugins|src)/.*\.py$

  • id: check-coverage name: Verify Test Coverage entry: python3 scripts/check_coverage.py language: system pass_filenames: false files: ^(plugins|src)/.*\.py$

```

CI Integration

Verify CI runs the same detailed checks:

```yaml

.github/workflows/quality.yml

name: Code Quality

on: [push, pull_request]

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

  - name: Set up Python
    uses: actions/setup-python@v5
    with:
      python-version: '3.12'

  - name: Install uv
    run: pip install uv

  - name: Install dependencies
    run: uv sync

  - name: Run Comprehensive Quality Checks
    run: ./scripts/check-all-quality.sh

  - name: Upload Coverage
    uses: codecov/codecov-action@v4
    with:
      files: ./coverage.xml

```

Troubleshooting

Hooks Too Slow

Solution: Only changed components are checked by default. For even faster commits:

```bash

Skip tests during development

SKIP=run-component-tests git commit -m "WIP: feature development"

Run tests manually when ready

./scripts/run-component-tests.sh --changed ```

Cache Issues

```bash

Clear pre-commit cache

uv run pre-commit clean

Clear component caches

find . -name "pycache" -type d -exec rm -rf {} + find . -name ".pytest_cache" -type d -exec rm -rf {} + find . -name ".mypy_cache" -type d -exec rm -rf {} + ```

Hook Failures

```bash

See detailed output

uv run pre-commit run --verbose --all-files

Run specific component checks manually

cd plugins/my-component make lint make typecheck make test ```

Import Errors in Tests

```toml

Ensure PYTHONPATH is set in pyproject.toml

[tool.pytest.ini_options] pythonpath = ["src"] ```

Type Checking Errors

```toml

Use per-module overrides for gradual typing

[[tool.mypy.overrides]] module = "legacy_module.*" disallow_untyped_defs = false ```

Best Practices

For New Projects

Start with strict settings from the beginning, as they are easier to maintain over time. We recommend configuring type checking with strict = true in your pyproject.toml and setting up testing early by including pytest in your pre-commit hooks. If you must skip any hooks, always document the reason for the exception.

For Existing Projects

When adding hooks to an existing codebase, use a gradual adoption strategy. Start with global checks and add component-specific checks later as you resolve legacy issues. Fix identified quality problems progressively and create a baseline to document the current state for tracking improvements. Use the --no-verify flag sparingly and only for true emergencies.

For Monorepos and Plugin Architectures

Standardize your development targets by using per-component Makefiles for linting, type checking, and testing. Centralize common settings in a root pyproject.toml while allowing for per-component overrides. Automate the detection of changed components to keep commit times fast, and use a progressive disclosure approach to show summaries first and detailed errors only on failure.

Complete Example: Python Monorepo

```yaml

.pre-commit-config.yaml

repos:

Layer 1: Fast Global Checks

• repo: https://github.com/pre-commit/pre-commit-hooks rev: v6.0.0 hooks:

  • id: trailing-whitespace
  • id: end-of-file-fixer
  • id: check-yaml
  • id: check-toml
  • id: check-json

• repo: https://github.com/astral-sh/ruff-pre-commit rev: v0.14.2 hooks:

  • id: ruff args: [--fix]
  • id: ruff-format

• repo: https://github.com/pre-commit/mirrors-mypy rev: v1.13.0 hooks:

  • id: mypy args: [--ignore-missing-imports]

• repo: https://github.com/PyCQA/bandit rev: 1.8.0 hooks:

  • id: bandit args: [-c, pyproject.toml]

Layer 2: Component-Specific Checks

• repo: local hooks:

  • id: run-component-lint name: Lint Changed Components entry: ./scripts/run-component-lint.sh language: system pass_filenames: false files: ^plugins/.*\.py$

  • id: run-component-typecheck name: Type Check Changed Components entry: ./scripts/run-component-typecheck.sh language: system pass_filenames: false files: ^plugins/.*\.py$

  • id: run-component-tests name: Test Changed Components entry: ./scripts/run-component-tests.sh language: system pass_filenames: false files: ^plugins/.*\.(py|md)$

Layer 3: Validation Hooks

• repo: local hooks:
  • id: validate-plugin-structure name: Validate Plugin Structure entry: python3 scripts/validate_plugins.py language: system pass_filenames: false files: ^plugins/.*$

```

Related Skills

• Skill(attune:project-init) - Full project initialization
• Skill(attune:workflow-setup) - GitHub Actions setup
• Skill(attune:makefile-generation) - Generate component Makefiles
• Skill(pensive:shell-review) - Audit shell scripts for exit code and safety issues

See Also

• Quality Gates Documentation - Detailed quality system guide
• Testing Guide - Testing best practices