Everything to know about pre-commit

Automate whenever possible

  • Guidelines
  • Code format
  • Static code analysis
  • …

How to manage all these tools

  • Shell scripts for every tool?
  • Makefiles or similar frameworks?
  • Git hooks calling the scripts?

Drawbacks

  • Script/tool maintenance
  • Tooling setup/dependencies
  • Forgot to run the checks locally

pre-commit

A framework for managing and maintaining multi-language pre-commit hooks

pre-commit.com

Features

  • Automatically setup all dependencies in virtual environments without root access required
  • Manage all tools in a single configuration file .pre-commit-config.yaml

Configuration

default_stages: [commit]
repos:
  - repo: https://github.com/pre-commit/pre-commit-hooks
    rev: v4.1.0
    hooks:
      - id: trailing-whitespace
      - id: end-of-file-fixer
  - repo: https://github.com/psf/black
    rev: 22.1.0
    hooks:
      - id: black
        language_version: python3
        args: [--quiet]

Usage

  1. Setup once: pre-commit install
  2. Now pre-commit will run automatically on git commit

Optional Usage

Manually run pre-commit

  • All files: pre-commit run --all-files
  • Selected files: pre-commit run --files <list of files>
  • Selected hooks: pre-commit run black

Output

pre-commit run --all-files
[INFO] Initializing environment for https://github.com/pre-commit/pre-commit-hooks.
[INFO] Initializing environment for https://github.com/psf/black.
[INFO] Installing environment for https://github.com/pre-commit/pre-commit-hooks.
[INFO] Once installed this environment will be reused.
[INFO] This may take a few minutes...
[INFO] Installing environment for https://github.com/psf/black.
[INFO] Once installed this environment will be reused.
[INFO] This may take a few minutes...
Check Yaml...............................................................Passed
Fix End of Files.........................................................Passed
Trim Trailing Whitespace.................................................Failed
- hook id: trailing-whitespace
- exit code: 1

Files were modified by this hook. Additional output:

Fixing sample.py

black....................................................................Passed

Summary