Pre-commit¶

Git hook scripts are useful for identifying simple issues before submission to code review. Pre-commit runs on every commit to automatically point out issues in code such as trailing whitespace, and debug statements. By pointing these issues out before code review, this allows a code reviewer to focus on the architecture of a change while not wasting time with trivial style nitpicks.

Pre-commit is a multi-language package manager for pre-commit hooks. You specify a list of hooks you want and pre-commit manages the installation and execution of any hook written in any language before every commit. pre-commit is specifically designed to not require root access. If one of your developers doesn’t have node installed but modifies a JavaScript file, pre-commit automatically handles downloading and building node to run eslint without root.

For further information visit https://pre-commit.com/

Installation¶

$ poetry add pre-commit --dev
$ pre-commit install

Configuration¶

Create a .pre-commit-config.yaml file and add the following:

repos:
  - repo: https://github.com/pre-commit/pre-commit-hooks
    rev: v3.2.0
    hooks:
      - id: check-added-large-files
        name: Check for added large files
        description: Prevent giant files from being committed
        entry: check-added-large-files

      - id: check-ast
        name: Check python ast
        description: Simply check whether the files parse as valid python.
        entry: check-ast
        types: [python]

      - id: check-case-conflict
        name: Check for case conflicts
        description: Check for files that would conflict in case-insensitive filesystems
        entry: check-case-conflict

      - id: check-merge-conflict
        name: Check for merge conflicts
        description: Check for files that contain merge conflict strings.
        entry: check-merge-conflict
        types: [text]

      - id: debug-statements
        name: Debug Statements (Python)
        description: Check for debugger imports and py37+ `breakpoint()` calls in python source.
        entry: debug-statement-hook
        types: [python]

      - id: end-of-file-fixer
        name: Fix End of Files
        description: Ensures that a file is either empty, or ends with one newline.
        entry: end-of-file-fixer
        types: [text]
        stages: [commit, push, manual]

      - id: mixed-line-ending
        name: Mixed line ending
        description: Replaces or checks mixed line ending
        entry: mixed-line-ending
        types: [text]

      - id: no-commit-to-branch
        name: "Don't commit to branch"
        entry: no-commit-to-branch
        pass_filenames: false
        always_run: true

      - id: trailing-whitespace
        name: Trim Trailing Whitespace
        description: This hook trims trailing whitespace.
        entry: trailing-whitespace-fixer
        types: [text]
        stages: [commit, push, manual]

  - repo: https://github.com/asottile/add-trailing-comma
    rev: v2.0.1
    hooks:
      - id: add-trailing-comma
        args: [--py36-plus]

  - repo: https://github.com/psf/black
    rev: 20.8b1
    hooks:
      - id: black
        language_version: python3

  - repo: https://github.com/pycqa/isort
    rev: 5.5.4
    hooks:
      - id: isort

  - repo: https://gitlab.com/pycqa/flake8
    rev: 3.8.4
    hooks:
      - id: flake8

  - repo: https://github.com/pre-commit/mirrors-mypy
    rev: v0.782
    hooks:
      - id: mypy
        exclude: docs

  - repo: https://github.com/prettier/prettier
    rev: 2.1.2
    hooks:
      - id: prettier

Usage¶

Pre-commit will run automatically every time you make a commit.

$ git add .
$ git commit

You can run it manually as well.

$ pre-commit run

If you want to run pre-commit on all your files:

$ pre-commit run --all-files

Or if you want to run pre-commit on specific files/folders:

$ pre-commit run --files python_lifecycle_training tests

You can also run a specific hook:

$ pre-commit run flake8 --files tests/calculator/test_simple.py

Useful Commands¶

You can update your hooks to the latest version automatically by running:

$ pre-commit autoupdate

Advanced features¶

Temporarily disable hooks¶

$ SKIP=flake8,mypy git commit

Automatically enable pre-commit for all repositories¶

$ git config --global init.templateDir ~/.git-template
$ pre-commit init-templatedir ~/.git-template

Add a badge¶

.. image:: https://img.shields.io/badge/pre--commit-enabled-brightgreen?logo=pre-commit&logoColor=white
    :target: https://github.com/pre-commit/pre-commit
    :alt: pre-commit

Note

You can remove the unused imports in test_simple.py to pass flake8 tests. You can remove flake8, black, isort and mypy dependencies as well because pre-commit has them all covered

Next Step¶

To move on to the next step commit or stash your changes then checkout to the branch setup/cli/fire

$ git stash
$ git checkout setup/cli/fire

Uninstall¶

$ pre-commit uninstall
$ poetry remove pre-commit --dev