leave-comment.yml

name: Leave a comment

on:
  workflow_run:
    workflows: ['Generate and Compare Docs']
    types: [completed]

permissions:
  contents: read
  actions: read

concurrency:
  group: ${{ github.workflow }}-${{ github.event.workflow_run.id }}
  cancel-in-progress: true

jobs:
  aggregate:
    name: Aggregate Comparison Results
    runs-on: ubuntu-latest
    permissions:
      pull-requests: write

    steps:
      - name: Harden Runner
        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
        with:
          egress-policy: block
          allowed-endpoints: >
            api.github.com:443

      - name: Download all comparison artifacts
        uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c # v8.0.1
        with:
          run-id: ${{ github.event.workflow_run.id }}
          github-token: ${{ secrets.GITHUB_TOKEN }}
          path: results

      - name: Combine results
        id: combine
        # Even if the cat fails (no files found), we don't want to fail the workflow
        continue-on-error: true
        run: |
          {
            echo "combined<<EOF"
            cat results/*/comparison.txt
            echo "EOF"
          } >> "$GITHUB_OUTPUT"

      - name: Resolve Pull Request Number
        id: pr
        if: steps.combine.outputs.combined
        uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
        with:
          script: |
            const run = context.payload.workflow_run;

            // 1. For same-repo Pull Requests the run is already linked to its PR(s).
            if (run.pull_requests && run.pull_requests.length) {
              core.setOutput('number', run.pull_requests[0].number);
              return;
            }

            // 2. For forks that list is empty, so find the open Pull Request who has the
            // correct branch information
            const match = await github.rest.pulls.list({
              owner: context.repo.owner,
              repo: context.repo.repo,
              state: 'open',
              head: `${run.head_repository.owner.login}:${run.head_branch}`,
              sort: 'updated',
              direction: 'desc',
              per_page: 1,
            }).then(r => r.data[0]);

            if (!match) {
              core.info(`No open pull request found for HEAD ${run.head_sha}`);
              return;
            }

            core.setOutput('number', match.number);

      - name: Add Comment to PR
        if: steps.combine.outputs.combined && steps.pr.outputs.number != ''
        uses: thollander/actions-comment-pull-request@24bffb9b452ba05a4f3f77933840a6a841d1b32b # v3.0.1
        with:
          comment-tag: compared
          message: ${{ steps.combine.outputs.combined }}
          pr-number: ${{ steps.pr.outputs.number }}