Pre-commit hooks are great to reduce the feedback loop for things like linting and auto-formatting. Git supports them out of the box, but they are not easy to share across all developers working on a project, they need to be installed by each developers.
Several tools exist to solve this problem, but my favorite is pre-commit. Itβs written in Python, but it aims at being language agnostic. It saves your setup in a config file and developers can install all of them with a single command.
Each tool is referenced by their github repo and tag to install, which is great because each tool is pinned to a specific version. However, I usually have the tool versions already elsewhere in my repository, for example in requirements.txt
, causing some duplication. The main project dependencies are automatically updated with Dependabot, PyUP or Renovate but none of these tools supports the pre-commit config file. After a while, it's easy to end up with versions discrepancies.
That is until this week-end, where I stumbled upon the autoupdate
command from pre-commit. Iβm not sure how I missed this before, it looks like itβs been part of pre-commit for a really long time. By combining this with the power of Github actions, I was able to get it to send me a pull request each time a new version is available:
name: Pre-commit auto-update
on:
schedule:
- cron: '0 0 * * *'
jobs:
auto-update:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v2
- name: Set up Python
uses: actions/setup-python@v2
with:
python-version: 3.8
- name: Install pre-commit
run: pip install pre-commit
- name: Run pre-commit autoupdate
run: pre-commit autoupdate
- name: Create Pull Request
uses: peter-evans/create-pull-request@v2
with:
token: ${{ secrets.CPR_GITHUB_TOKEN }}
branch: update/pre-commit-autoupdate
title: Auto-update pre-commit hooks
commit-message: Auto-update pre-commit hooks
body: |
Update versions of tools in pre-commit
configs to latest version
labels: dependencies
This workflow is scheduled every day at midnight, runs pre-commit autoupdate
and sends a pull request if there are any changes.
The piece that required a bit of fiddling is the action creating the pull request, partly to get commit message, title, content and labels right, but mostly because I initially used secrets.GITHUB_TOKEN
as token, but it wouldn't trigger the CI build for that pull request.
It's a limitation which is well documented on the action's README, and is intentional from Github. I chose the solution to create a PAT scoped to repo
and added it to the secrets as CPR_GITHUB_TOKEN
. It's deployed and running on the repo of django-codemod
.
The pull request action has fixed inputs, so it will create one pull request at a time for all updates. If several tools get a new version, they would all be updated at once, and if a pull request already exists, it would receive more updates. This is not necessarily a bad thing, but if one tool breaks the build due to new linting rules, all are stuck.
Maybe I'll look into making the pull request content a bit more dynamic, but for now it does the job I need to. I'm also planning to add this to my Cookiecutter template for Python package, so I can get it for all my new projects.
I hope this can help folks keep their pre-commit hook up to date, maybe this will become obsolete when pre-commit CI is ready, or maybe it will be a cheaper and simpler alternative
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