Black Formatting workflow (tanghaibao/jcvi)

The Black Formatting workflow from tanghaibao/jcvi, explained and optimized by Latchkey.

What it does

This is the Black Formatting workflow from the tanghaibao/jcvi repository, a real project running GitHub Actions. It is shown here with attribution under its BSD-2-Clause license.

Below, Latchkey shows a faster, safer version produced by its optimization engine.

The workflow

name: Black Formatting
on: [pull_request]
jobs:
  black:
    # Only run if not from dependabot AND not from a fork
    if: ${{ github.actor != 'dependabot[bot]' && github.event.pull_request.head.repo.fork != true }}
    runs-on: ubuntu-latest
    permissions:
      contents: write
      pull-requests: write
    steps:
      - uses: actions/checkout@v7
        with:
          ref: ${{ github.sha }}
          token: ${{ secrets.GITHUB_TOKEN }}
      - name: Black Code Formatter
        uses: psf/black@stable
        with:
          options: "--verbose"
          src: "."
      - name: Commit changes
        if: success()
        uses: stefanzweifel/git-auto-commit-action@v7
        id: auto-commit-action
        with:
          commit_message: "Style fixes by Black"

The same workflow, on Latchkey

Removes redundant runs and caps runaway jobs. Added and changed lines are highlighted.

name: Black Formatting
on: [pull_request]
concurrency:
  group: ${{ github.workflow }}-${{ github.ref }}
  cancel-in-progress: true
 
jobs:
  black:
    timeout-minutes: 30
    # Only run if not from dependabot AND not from a fork
    if: ${{ github.actor != 'dependabot[bot]' && github.event.pull_request.head.repo.fork != true }}
    runs-on: latchkey-small
    permissions:
      contents: write
      pull-requests: write
    steps:
      - uses: actions/checkout@v7
        with:
          ref: ${{ github.sha }}
          token: ${{ secrets.GITHUB_TOKEN }}
      - name: Black Code Formatter
        uses: psf/black@stable
        with:
          options: "--verbose"
          src: "."
      - name: Commit changes
        if: success()
        uses: stefanzweifel/git-auto-commit-action@v7
        id: auto-commit-action
        with:
          commit_message: "Style fixes by Black"
 

What changed

• Run on Latchkey managed runners with one line (runs-on), which apply the fixes below automatically and self-heal transient failures. This example uses latchkey-small; pick the runner size that fits the job.
• Cancel superseded runs when a branch or PR gets a newer push.
• Add a job timeout so a hung step cannot burn hours of runner time.

2 third-party actions are referenced by a movable tag. Pin them to the commit SHA (Latchkey resolves and applies this automatically) so a repointed tag cannot change what runs.

This workflow runs 1 job per trigger. On Latchkey the same minutes cost up to 58% less than GitHub-hosted, with zero queue time.

Actions used in this workflow