FormatCheck.yml

name: "Reusable Format Checking Workflow"

on:
  workflow_call:
    inputs:
      julia-version:
        description: "Julia version"
        default: "1"
        required: false
        type: string

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

# This workflow is designed to be called from a `pull_request` trigger (NOT
# `pull_request_target`). It runs with a read-only token and no secrets, so it
# is safe to check out and inspect code from forks. It never posts comments;
# instead the required formatting changes are reported in the job summary and
# the job fails, which surfaces as a red check on the PR.
jobs:
  format-check:
    name: "Runic"
    runs-on: ubuntu-latest

    permissions:
      contents: read

    steps:
      - name: Check out repository
        uses: actions/checkout@v5
        with:
          ref: ${{ github.event.pull_request.head.ref }}
          repository: ${{ github.event.pull_request.head.repo.full_name }}
          fetch-depth: 0

      - name: Add upstream remote
        run: |
          git remote add upstream https://github.com/${{ github.repository }}
          git fetch upstream

      - name: Setup Julia
        uses: julia-actions/setup-julia@v2
        with:
          version: ${{ inputs.julia-version }}
          arch: 'x64'

      - uses: julia-actions/cache@v2

      - name: Install Runic
        run: |
          julia --project=@runic -e 'using Pkg; Pkg.add("Runic")'
          curl -o git-runic https://raw.githubusercontent.com/fredrikekre/Runic.jl/master/bin/git-runic
          chmod +x git-runic
          sudo mv git-runic /usr/local/bin

      - name: Run Runic
        id: runic
        run: |
          set +e
          MERGE_BASE=$(git merge-base upstream/${{ github.base_ref }} HEAD) || exit 1
          DIFF=$(git runic --diff $MERGE_BASE)
          EXIT_CODE=$?

          echo "exit_code=$EXIT_CODE" >> $GITHUB_OUTPUT
          echo "diff<<EOF" >> $GITHUB_OUTPUT
          echo "$DIFF" >> $GITHUB_OUTPUT
          echo "EOF" >> $GITHUB_OUTPUT

          # if Runic itself errored (exit code 2), bail out
          [ $EXIT_CODE -eq 2 ] && exit 1 || exit 0

      - name: Report formatting suggestions
        if: steps.runic.outputs.exit_code == 1
        run: |
          cat >> "$GITHUB_STEP_SUMMARY" <<'EOF'
          ## :art: Formatting changes required

          This PR does not meet the project's style guidelines.
          Run [Runic](https://github.com/fredrikekre/Runic.jl) locally to apply the changes:

          ```
          git runic ${{ github.base_ref }}
          ```

          <details>
          <summary>Suggested changes</summary>

          ```diff
          ${{ steps.runic.outputs.diff }}
          ```

          </details>
          EOF

      - name: Report success
        if: steps.runic.outputs.exit_code == 0
        run: |
          echo "### :white_check_mark: Formatting OK" >> "$GITHUB_STEP_SUMMARY"

      - name: Propagate exit code
        run: exit ${{ steps.runic.outputs.exit_code }}