coverage-comment.yaml

###========================================
##  Coverage PR Comment (via workflow_run)
#==========================================
# This workflow runs after the CI workflow completes and posts the
# test coverage report as a PR comment. It uses `workflow_run` so that
# it always executes in the context of the base repository with write
# permissions — this is required for fork-based PRs where the
# GITHUB_TOKEN is read-only.
#
# Ref: https://docs.github.com/en/actions/writing-workflows/choosing-when-your-workflow-runs/events-that-trigger-workflows#workflow_run

name: Coverage comment

on:
  workflow_run:
    workflows: ["CI"]
    types:
      - completed

permissions:
  pull-requests: write

jobs:
  comment:
    name: Post coverage comment
    runs-on: ubuntu-latest
    # Only run when the triggering workflow was a PR and produced artifacts.
    if: >-
      github.event.workflow_run.event == 'pull_request'
    steps:
      - name: Download coverage artifact
        id: download
        uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
        with:
          script: |
            const fs = require('fs');
            // List artifacts for the triggering workflow run
            const artifacts = await github.rest.actions.listWorkflowRunArtifacts({
              owner: context.repo.owner,
              repo: context.repo.repo,
              run_id: context.payload.workflow_run.id,
            });
            const match = artifacts.data.artifacts.find(a => a.name === 'coverage-report');
            if (!match) {
              core.setOutput('found', 'false');
              console.log('No coverage-report artifact found — skipping.');
              return;
            }
            const download = await github.rest.actions.downloadArtifact({
              owner: context.repo.owner,
              repo: context.repo.repo,
              artifact_id: match.id,
              archive_format: 'zip',
            });
            fs.writeFileSync('/tmp/coverage-report.zip', Buffer.from(download.data));
            core.setOutput('found', 'true');

      - name: Extract artifact
        if: steps.download.outputs.found == 'true'
        run: |
          mkdir -p /tmp/coverage-artifact
          unzip -o /tmp/coverage-report.zip -d /tmp/coverage-artifact

      - name: Post PR comment
        if: steps.download.outputs.found == 'true'
        uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
        with:
          script: |
            const fs = require('fs/promises')

            // 1. Read artifact data
            const prNumber = parseInt(
              (await fs.readFile('/tmp/coverage-artifact/pr_number', 'utf8')).trim()
            );
            const threshold = (await fs.readFile('/tmp/coverage-artifact/threshold', 'utf8')).trim();
            const newCovStr = (await fs.readFile('/tmp/coverage-artifact/new_coverage', 'utf8')).trim();
            const prevCovStr = (await fs.readFile('/tmp/coverage-artifact/prev_coverage', 'utf8')).trim();

            let reportContent = "No coverage report generated (Build likely failed).";
            try {
              reportContent = await fs.readFile('/tmp/coverage-artifact/coverage_report.txt', 'utf8');
            } catch (e) {
              console.log("Could not read coverage report file:", e.message);
            }

            // 2. Calculate status
            const thresholdVal = parseFloat(threshold) || 0;
            const newCov = parseFloat(newCovStr);

            let overallStatus = "⚠️ SKIPPED (Build Failed?)";
            if (!isNaN(newCov)) {
              if (thresholdVal > newCov) {
                overallStatus = `❌ FAIL: Coverage (${newCov}%) < Threshold (${thresholdVal}%)`;
              } else {
                overallStatus = "✅ PASS";
              }
            }

            // 3. Build comment body
            const comment = `### 🔬 Go Test Coverage Report

            #### Summary

            | Coverage Type          | Result                                 |
            | ---------------------- | -------------------------------------- |
            | Threshold              | ${thresholdVal}%                       |
            | Previous Test Coverage | ${prevCovStr || 'Unknown'}%            |
            | New Test Coverage      | ${newCovStr || 'Unknown'}%             |

            #### Status

            ${overallStatus}

            #### Detail

            <details><summary>Show New Coverage</summary>

            \`\`\`
            ${reportContent}
            \`\`\`

            </details>
            `;

            // 4. Minimize old bot comments
            const { data: comments } = await github.rest.issues.listComments({
              ...context.repo,
              issue_number: prNumber,
            });
            const botComments = comments.filter(c =>
              c.user.type === 'Bot' &&
              c.body.includes('Go Test Coverage Report')
            );
            for (const botComment of botComments) {
              const query = `mutation {
                minimizeComment(input: {classifier: OUTDATED, subjectId: "${botComment.node_id}"}) {
                  clientMutationId
                }
              }`
              await github.graphql(query)
            }

            // 5. Create new comment
            await github.rest.issues.createComment({
              ...context.repo,
              issue_number: prNumber,
              body: comment,
            })