pre-commit-action

Composite action that runs pre-commit hooks against the PR diff and posts a sticky comment with the result.

Replaces the style.yaml boilerplate currently duplicated across ~20 two-inc repos.

Usage

Copy this workflow verbatim into .github/workflows/style.yaml:

name: Style

on:
  pull_request:
    types: [opened, synchronize, reopened]

concurrency:
  group: pre-commit-${{ github.ref_name }}
  cancel-in-progress: true

jobs:
  pre-commit:
    runs-on: ${{ vars.RUNNER_STANDARD }}
    timeout-minutes: 20
    permissions:
      contents: read
      pull-requests: write
    steps:
      - uses: two-inc/pre-commit-action@main
        with:
          python-version: "3.12"

Inputs

Input	Default	Description
python-version	3.12	Python version to install
github-token	${{ github.token }}	Token used to post the sticky comment
node-version	unset	If set, install Node.js of this version and run npm ci before pre-commit. Needed for hybrid Python+Node repos whose hooks import packages from node_modules.

Behaviour

• Checks out the PR with full history (fetch-depth: 0) so pre-commit can diff against origin/${{ github.base_ref }}.
• Installs uv with caching enabled, sets up Python.
• Runs uvx pre-commit run --from-ref ... --to-ref ... against the PR diff. Pre-commit is installed in an ephemeral environment; it manages each hook's isolated environment itself.
• Posts the result as a sticky PR comment identified by the pre-commit header marker — the comment is updated in place across pushes instead of deleted and recreated.
• Exits with pre-commit's exit code so the job reflects pass/fail.

PIP_EXTRA_INDEX_URL

The pre-commit run step exports PIP_EXTRA_INDEX_URL=https://europe-python.pkg.dev/tillit-api/two-pypi/simple/ so that hooks using language: python + additional_dependencies: ["two-dev-cli"] (or any other internal package) can install without extra wiring on the caller side. The index is anonymously readable, so it's harmless for repos that don't use internal packages.

If a local hook needs to shell out to a two-inc CLI (e.g. two lint), declare it as:

- repo: local
  hooks:
    - id: two-lint
      name: two-lint
      language: python
      entry: two lint
      additional_dependencies: ["two-dev-cli"]
      pass_filenames: false

Do not use language: system for these hooks — the action runs pre-commit via uvx without syncing the project venv, so system hooks that shell out to project-installed binaries won't find them.

Migration notes

Alongside adopting this action, consumer repos should:

• Remove pre-commit from [dependency-groups].dev — not needed. The action runs pre-commit via uvx, which installs it on the fly. Pre-commit isn't actually a project dependency.
• Bump stale hook revisions if any use the removed language: python_venv alias. Latest pre-commit (4.x) rejects this — it was deprecated in favour of language: python. For docformatter, upgrade to v1.7.8 or later.

The action deliberately drops two things that appeared in many existing style.yaml files:

• GCP Artifact Registry auth — not needed. uvx pre-commit pulls pre-commit from public PyPI; no private-index access required.
• uv sync --group dev — not needed. uvx handles the ephemeral environment.