CI workflow (rubocop/rubocop)

The CI workflow from rubocop/rubocop, explained and optimized by Latchkey.

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Source: rubocop/rubocop.github/workflows/rubocop.ymlLicense MITView source

What it does

This is the CI workflow from the rubocop/rubocop repository, a real project running GitHub Actions. It is shown here with attribution under its MIT license.

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

The workflow

workflow (.yml)

name: CI

on:
  push:
    branches:
      - master
  pull_request:
  workflow_dispatch:

permissions:  # added using https://github.com/step-security/secure-workflows
  contents: read

concurrency:
  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
  cancel-in-progress: true

jobs:
  spec-ubuntu:
    name: Spec - ubuntu ${{ matrix.ruby }}
    runs-on: ubuntu-latest
    strategy:
      fail-fast: false
      matrix:
        ruby: ['2.7', '3.0', '3.1', '3.2', '3.3', '3.4', '4.0', 'head']

    steps:
      - uses: actions/checkout@v7
      - uses: ruby/setup-ruby@v1
        with:
          ruby-version: ${{ matrix.ruby }}
          bundler-cache: true
      - name: Check requiring libraries successfully
        # See https://github.com/rubocop/rubocop/pull/4523#issuecomment-309136113
        run: ruby -I lib -r bundler/setup -r rubocop -e 'exit 0'
      - name: spec
        env:
          CI_RUBY_VERSION: ${{ matrix.ruby }}
          STRICT_WARNINGS: 1
        run: bundle exec rake spec

  spec-jruby:
    name: Spec - JRuby
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v7
      - uses: ruby/setup-ruby@v1
        with:
          ruby-version: 'jruby' # Latest stable JRuby version
          bundler-cache: true
      - name: spec
        run: bundle exec rake spec

  spec-windows:
    needs: spec-ubuntu # Don't spend CI resources on slow Windows specs if CI won't pass anyway.
    name: Spec - windows ${{ matrix.ruby }}
    runs-on: windows-latest
    strategy:
      fail-fast: false
      matrix:
        ruby:
          - '2.7'  # Oldest supported version
          - 'ruby' # Latest stable CRuby version

    steps:
      - uses: actions/checkout@v7
      - uses: ruby/setup-ruby@v1
        with:
          ruby-version: ${{ matrix.ruby }}
          bundler-cache: true
      - name: Check requiring libraries successfully
        # See https://github.com/rubocop/rubocop/pull/4523#issuecomment-309136113
        run: ruby -I lib -r bundler/setup -r rubocop -e 'exit 0'
      - name: spec
        env:
          CI_RUBY_VERSION: ${{ matrix.ruby }}
        run: bundle exec rake spec

  ascii_spec:
    name: Ascii Spec - ${{ matrix.os }} ${{ matrix.ruby }}
    runs-on: ${{ matrix.os }}-latest

    strategy:
      fail-fast: false
      matrix:
        os: [ubuntu, windows]
        ruby:
          - '2.7'  # Oldest supported version
          - 'ruby' # Latest stable CRuby version

    steps:
      - uses: actions/checkout@v7
      - uses: ruby/setup-ruby@v1
        with:
          ruby-version: ${{ matrix.ruby }}
          bundler-cache: true
      - name: ascii_spec
        env:
          CI_RUBY_VERSION: ${{ matrix.ruby }}
        run: bundle exec rake ascii_spec

  documentation_check:
    name: Documentation Check
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v7
      - uses: ruby/setup-ruby@v1
        with:
          ruby-version: ruby # Latest stable CRuby version
          bundler-cache: true
      - name: Check documentation syntax
        run: bundle exec rake documentation_syntax_check

  prism:
    runs-on: ubuntu-latest
    name: Prism
    steps:
      - uses: actions/checkout@v7
      - uses: ruby/setup-ruby@v1
        with:
          # Specify the minimum Ruby version 2.7 required for Prism to run.
          ruby-version: 2.7
          bundler-cache: true
      - name: spec
        env:
          PARSER_ENGINE: parser_prism
        run: bundle exec rake prism_spec

The same workflow, on Latchkey

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

name: CI
 
on:
  push:
    branches:
      - master
  pull_request:
  workflow_dispatch:
 
permissions:  # added using https://github.com/step-security/secure-workflows
  contents: read
 
concurrency:
  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
  cancel-in-progress: true
 
jobs:
  spec-ubuntu:
    timeout-minutes: 30
    name: Spec - ubuntu ${{ matrix.ruby }}
    runs-on: latchkey-small
    strategy:
      fail-fast: false
      matrix:
        ruby: ['2.7', '3.0', '3.1', '3.2', '3.3', '3.4', '4.0', 'head']
 
    steps:
      - uses: actions/checkout@v7
      - uses: ruby/setup-ruby@v1
        with:
          ruby-version: ${{ matrix.ruby }}
          bundler-cache: true
      - name: Check requiring libraries successfully
        # See https://github.com/rubocop/rubocop/pull/4523#issuecomment-309136113
        run: ruby -I lib -r bundler/setup -r rubocop -e 'exit 0'
      - name: spec
        env:
          CI_RUBY_VERSION: ${{ matrix.ruby }}
          STRICT_WARNINGS: 1
        run: bundle exec rake spec
 
  spec-jruby:
    timeout-minutes: 30
    name: Spec - JRuby
    runs-on: latchkey-small
    steps:
      - uses: actions/checkout@v7
      - uses: ruby/setup-ruby@v1
        with:
          ruby-version: 'jruby' # Latest stable JRuby version
          bundler-cache: true
      - name: spec
        run: bundle exec rake spec
 
  spec-windows:
    timeout-minutes: 30
    needs: spec-ubuntu # Don't spend CI resources on slow Windows specs if CI won't pass anyway.
    name: Spec - windows ${{ matrix.ruby }}
    runs-on: windows-latest
    strategy:
      fail-fast: false
      matrix:
        ruby:
          - '2.7'  # Oldest supported version
          - 'ruby' # Latest stable CRuby version
 
    steps:
      - uses: actions/checkout@v7
      - uses: ruby/setup-ruby@v1
        with:
          ruby-version: ${{ matrix.ruby }}
          bundler-cache: true
      - name: Check requiring libraries successfully
        # See https://github.com/rubocop/rubocop/pull/4523#issuecomment-309136113
        run: ruby -I lib -r bundler/setup -r rubocop -e 'exit 0'
      - name: spec
        env:
          CI_RUBY_VERSION: ${{ matrix.ruby }}
        run: bundle exec rake spec
 
  ascii_spec:
    timeout-minutes: 30
    name: Ascii Spec - ${{ matrix.os }} ${{ matrix.ruby }}
    runs-on: ${{ matrix.os }}-latest
 
    strategy:
      fail-fast: false
      matrix:
        os: [ubuntu, windows]
        ruby:
          - '2.7'  # Oldest supported version
          - 'ruby' # Latest stable CRuby version
 
    steps:
      - uses: actions/checkout@v7
      - uses: ruby/setup-ruby@v1
        with:
          ruby-version: ${{ matrix.ruby }}
          bundler-cache: true
      - name: ascii_spec
        env:
          CI_RUBY_VERSION: ${{ matrix.ruby }}
        run: bundle exec rake ascii_spec
 
  documentation_check:
    timeout-minutes: 30
    name: Documentation Check
    runs-on: latchkey-small
    steps:
      - uses: actions/checkout@v7
      - uses: ruby/setup-ruby@v1
        with:
          ruby-version: ruby # Latest stable CRuby version
          bundler-cache: true
      - name: Check documentation syntax
        run: bundle exec rake documentation_syntax_check
 
  prism:
    timeout-minutes: 30
    runs-on: latchkey-small
    name: Prism
    steps:
      - uses: actions/checkout@v7
      - uses: ruby/setup-ruby@v1
        with:
          # Specify the minimum Ruby version 2.7 required for Prism to run.
          ruby-version: 2.7
          bundler-cache: true
      - name: spec
        env:
          PARSER_ENGINE: parser_prism
        run: bundle exec rake prism_spec

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.
Add a job timeout so a hung step cannot burn hours of runner time.

1 third-party action is referenced by a movable tag. Pin it to the commit SHA (Latchkey resolves and applies this automatically) so a repointed tag cannot change what runs.

This workflow runs 6 jobs (17 with the matrix expanded) per trigger. On Latchkey the same minutes cost up to 58% less than GitHub-hosted, with zero queue time.

Actions used in this workflow

actions/checkout ruby/setup-ruby