check-whitespace.yml

name: Whitespace Check

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

jobs:
  check-whitespace:
    runs-on: ubuntu-latest
    permissions:
      contents: read
      pull-requests: write
    steps:
      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
        with:
          ref: ${{ github.event.pull_request.head.sha }}
          fetch-depth: 0

      - name: Check for whitespace errors
        id: check
        run: |
          # Compare PR branch against base branch
          BASE_SHA=${{ github.event.pull_request.base.sha }}
          HEAD_SHA=${{ github.event.pull_request.head.sha }}

          echo "Checking commits from $BASE_SHA to $HEAD_SHA"

          # git diff --check returns non-zero if whitespace errors exist
          if git diff --check "$BASE_SHA" "$HEAD_SHA" > errors.txt 2>&1; then
            echo "has_errors=false" >> $GITHUB_OUTPUT
            echo "### No Whitespace Issues" >> $GITHUB_STEP_SUMMARY
          else
            echo "has_errors=true" >> $GITHUB_OUTPUT

            # Build summary
            {
              echo "### Whitespace Issues Found"
              echo ""
              echo "Files with whitespace errors (trailing spaces, spaces before tabs):"
              echo ""
              echo '```'
              cat errors.txt
              echo '```'
              echo ""
              echo "**To fix:** Run \`git rebase --whitespace=fix $BASE_SHA\` then force push."
            } >> $GITHUB_STEP_SUMMARY

            # Save for PR comment (using heredoc for multiline)
            {
              echo 'ERRORS<<EOF'
              cat errors.txt
              echo 'EOF'
            } >> $GITHUB_ENV
          fi

      # Always look for existing comment (to update or delete)
      - name: Find existing comment
        uses: peter-evans/find-comment@3eae4d37986fb5a8592848f6a574fdf654e61f9e # v3.1.0
        id: find-comment
        with:
          issue-number: ${{ github.event.pull_request.number }}
          comment-author: 'github-actions[bot]'
          body-includes: 'whitespace errors'

      # Delete old failure comment when check passes
      - name: Delete old comment if check passes
        if: steps.check.outputs.has_errors == 'false' && steps.find-comment.outputs.comment-id != ''
        uses: actions/github-script@60a0d83039c74a4aee543508d2ffcb1c3799cdea # v7.0.1
        with:
          script: |
            await github.rest.issues.deleteComment({
              owner: context.repo.owner,
              repo: context.repo.repo,
              comment_id: ${{ steps.find-comment.outputs.comment-id }}
            });

      # Create or update failure comment
      - name: Create or update PR comment
        if: steps.check.outputs.has_errors == 'true'
        uses: peter-evans/create-or-update-comment@71345be0265236311c031f5c7866368bd1eff043 # v4.0.0
        with:
          comment-id: ${{ steps.find-comment.outputs.comment-id }}
          issue-number: ${{ github.event.pull_request.number }}
          edit-mode: replace
          body: |
            ## Whitespace Check Failed

            Files in this PR have whitespace errors (trailing spaces, spaces before tabs, etc.):

            ```
            ${{ env.ERRORS }}
            ```

            ### How to fix
            ```bash
            # Automatically fix whitespace in your branch
            git rebase --whitespace=fix ${{ github.event.pull_request.base.sha }}
            git push --force-with-lease
            ```

            ---
            *Checked at: ${{ github.event.pull_request.head.sha }}*

      - name: Fail if errors
        if: steps.check.outputs.has_errors == 'true'
        run: exit 1