Using Github actions for pants check

[aebrahim]

How do people do their presubmits on GitHub actions, and is there any way to make them quick?

This is the setup we use. It feels pretty hacky and homegrown, and the diff base does not work reliably.

on:
  pull_request:
    paths:
      - "**.py"
      - "**/BUILD"
      - "**.lock"
      - mypy.ini
      - pants.*
      - .github/workflows/pants_code_quality.yml
      - 3rdparty/
  workflow_dispatch: null
  push:
    branches:
      - main
    paths:
      - "**.py"
      - "**/BUILD"
      - "**.lock"
      - mypy.ini
      - pants.*
      - .github/workflows/pants_code_quality.yml
      - 3rdparty/
name: Pants Pull Request
jobs:
  code_quality:
    runs-on: ubuntu-latest
    steps:
      - name: Git metrics
        id: git_metrics
        run: |
          if [ "${{ github.event_name }}" = "pull_request" ]; then
            echo "fetch_depth=$((${{ github.event.pull_request.commits }} + 1))" >> $GITHUB_OUTPUT
            echo "diff_base=${{ github.event.pull_request.base.sha }}" >> $GITHUB_OUTPUT
          elif [ "${{ github.event_name }}" = "push" ]; then
            echo "fetch_depth=2" >> $GITHUB_OUTPUT
            echo "diff_base=${{ github.event.before }}" >> $GITHUB_OUTPUT
          else
            echo "fetch_depth=1" >> $GITHUB_OUTPUT
            echo "diff_base=HEAD^" >> $GITHUB_OUTPUT
          fi
      - name: Checkout repo
        uses: actions/checkout@v6
        with:
          # The pull request base sha is right below the merge commit GH checked out for us
          fetch-depth: ${{ steps.git_metrics.outputs.fetch_depth }}
      - uses: actions/setup-python@v6
        with:
          python-version: '3.11'
      - name: Initialize Pants
        uses: pantsbuild/actions/init-pants@main
        with:
          base-branch: ${{ github.event.pull_request.base.ref || 'main' }}
          # The Python backend uses named_caches for Pip/PEX state,
          # so it is appropriate to invalidate on lockfile changes.
          named-caches-hash: ${{ hashFiles('3rdparty/python/*.lock') }}
          cache-lmdb-store: 'true'
      - name: Pants Peek
        run: pants --no-dynamic-ui --changed-since=${{ steps.git_metrics.outputs.diff_base }} --changed-dependents=direct peek --peek-output-file=/dev/null
      - name: Pants Lint
        run: pants --no-dynamic-ui --changed-since=${{ steps.git_metrics.outputs.diff_base }} --changed-dependents=direct lint
      - name: Pants Check
        run: pants --no-dynamic-ui --changed-since=${{ steps.git_metrics.outputs.diff_base }} --changed-dependents=direct check