Autohooks

Library for managing and writing git hooks in Python

Why?

Several outstanding libraries for managing and executing git hooks already exist. To name few: husky, lint-staged, precise-commits or pre-commit.

But either they need another interpreter besides python (like husky) or they are too ambiguous (like pre-commit). pre-commit is written in python but has support hooks written in all kind of languages. Also it maintains the dependencies by itself and doesn't install in the current environment.

Solution

Autohooks is a pure python library that installs a minimal executable git hook. If autohooks isn't installed in your current python path the hooks aren't executed. So autohooks is always opt-in by installing the package into your current development environment. It would be even possible to run different versions of autohooks by switching the environment.

Autohooks doesn't interfere with your work. If autohooks can't be run or fails executing a plugin, an error is shown only and the git hook will proceed.

Installation

For the installation of autohooks three steps are necessary:

1. Install the autohooks package into your current environment
2. Activate the git hooks
3. Configure the plugins to be run

Install autohooks python package

For installing the autohooks python package, using pipenv is highly recommended.

To install autohooks as a development dependency run

pipenv install --dev autohooks

Alternatively autohooks can be installed directly from GitHub

pipenv install --dev -e git+https://github.com/greenbone/autohooks#egg=autohooks

Activating the git hooks

If autohooks is installed from git or a source tarball, the git hooks should be activated automatically. The activation can be verified by running e.g. autohooks check.

Installing autohooks from a wheel package will NOT activate the git commit hooks.

To manually activate the git hooks you can run

pipenv run autohooks activate

Configure plugins to be run

To actually run an action on git hooks, autohooks plugins have to be installed and configured. To install e.g. python linting via pylint run

pipenv install --dev autohooks-plugin-pylint

Autohooks uses the pyproject.toml file specified in PEP518 for its configuration. Adding a [tool.autohooks] section allows to set python modules to be run on a specific git hook.

Example pyproject.toml:

[build-system]
requires = ["setuptools", "wheel"]

[tool.autohooks]
pre-commit = ["autohooks.plugins.black"]

Proposed Workflow

Using pipenv allows to install all dependencies and tools with a specific version into a virtual, easily removable Python environment. Therefore it's best to maintain autohooks also via pipenv. Because it is not required to build or run your software, it should be installed as a development dependency. Installing and activating autohooks doesn't actually run any check or formatting by itself. Therefore, it is required to choose and install a plugin.

If all these tasks have been resolved, the developers are able to install and activate autohooks with only one single command from your project's git repository:

pipenv install --dev

Because virtual environments are used for all dependencies including autohooks, the linting, formatting, etc. can only by done when running git commit within the virtual environment.

$ cd myproject
$ pipenv install --dev
$ pipenv shell
(myproject)$ git commit

The advantage of this process is, if the user is not running git commit within the active virtual environment, autohooks and its plugins are not executed.

$ cd myproject
$ git commit

This allows the user to choose whether to execute the hooks by activating the virtual environment or to ignore them by deactivating it.

Plugins

• Python code formatting via black

• Python code linting via pylint

How-to write a Plugin

Plugins need to be available in the Python import path. The easiest way to achieve this, is to upload a plugin to PyPI and install it via pip or pipenv.

Alternatively, a plugin can also be put into a .autohooks directory at the root directory of the git repository where the hooks should be executed.

An autohooks plugin is a Python module which provides a precommit function. The function must accept arbitrary keywords because the keywords are likely to change in future. Therefore using **kwargs is highly recommended. Currently only a config keyword argument is passed to the precommit function. E.g.

def precommit(**kwargs):
    config = kwargs.get('config')

The config can be used to receive settings from the pyproject.toml file. E.g.

[tool.autohooks.plugins.foo]
bar = 2

can be received with

def precommit(**kwargs):
    config = kwargs.get('config')
    default_value = 1
    setting = config
      .get('tool', 'autohooks', 'plugins', 'foo')
      .get_value('bar', default_value)
    return 0

With autohooks it is possible to write all kinds of plugins. Most common are plugins for linting and formatting.

Linting plugin

Usually the standard call sequence for a linting plugin is

1. get list of staged files
2. filter list of files for a specific file type
3. stash unrelated changes
4. apply checks on filtered list of files by calling some external tool
5. raise exception if something did go wrong
6. return 1 if check was not successful
7. stage changes made by the tool
8. unstash unrelated changes
9. return 0

Example plugin:

import subprocess

from autohooks.api import ok, fail
from autohooks.api.git import get_staged_status, stash_unstaged_changes
from autohooks.api.path import match

DEFAULT_INCLUDE = ('*.ext')


def get_include(config)
    if not config:
        return DEFAULT_INCLUDE

    config = config.get('tool', 'autohooks', 'plugins', 'foo')
    return config.get_value('include', DEFAULT_INCUDE)


def precommit(**kwargs):
    config = kwargs.get('config')
    include = get_include(config)

    files = [f for f in get_staged_status() if match(f.path, include)]

    if not files:
      # not files to lint
      return 0

    with stash_unstaged_changes(files):
        const failed = False
        for file in files:
            status = subprocess.call(['foolinter', str(file)])
            if status:
                fail('Could not validate {}'.format(str(file)))
                failed = True
            else:
                ok('Validated {}'.format(str(file)))

        return 1 if failed else 0

### Formatting plugin

Usually the standard call sequence for a formatting plugin is

1. get list of staged files
2. filter list of files for a specific file type
3. stash unrelated changes
4. apply formatting on filtered list of files by calling some external tool
5. raise exception if something did go wrong
6. stage changes made by the tool
7. unstash unrelated changes
8. return 0

Example plugin:
```python3
import subprocess

from autohooks.api import ok, error
from autohooks.api.git import (
    get_staged_status,
    stage_files_from_status_list,
    stash_unstaged_changes,
)
from autohooks.api.path import match

DEFAULT_INCLUDE = ('*.ext')


def get_include(config)
    if not config:
        return DEFAULT_INCLUDE

    config = config.get('tool', 'autohooks', 'plugins', 'bar')
    return config.get_value('include', DEFAULT_INCUDE)


def precommit(**kwargs):
    config = kwargs.get('config')
    include = get_include(config)

    files = [f for f in get_staged_status() if match(f.path, include)]

    if not files:
      # not files to format
      return 0

    with stash_unstaged_changes(files):
        for file in files:
            # run formatter and raise exception if it fails
            subprocess.run(['barformatter', str(file)], check=True)
            ok('Formatted {}'.format(str(file)))

        return 0

Maintainer

This project is maintained by Greenbone Networks GmbH.

Contributing

Your contributions are highly appreciated. Please create a pull request on GitHub. Bigger changes need to be discussed with the development team via the issues section at GitHub first.

License

Copyright (C) 2019 Greenbone Networks GmbH

Licensed under the GNU General Public License v3.0 or later.