CI: add failure reporter (workflow_run) scoped to jbrinkman/matrix-errors; aggregates artifacts and updates rolling issue

Signed-off-by: jbrinkman <[email protected]>

Author: jbrinkman

.github/workflows/report-failures.yml

@@ -0,0 +1,109 @@
+name: C# failure reporter
+
+on:
+    workflow_run:
+        workflows: ["C# tests"]
+        types: [completed]
+  branches: [jbrinkman/matrix-errors]
+
+permissions:
+    actions: read
+    contents: read
+    issues: write
+
+jobs:
+    report:
+        # Only handle scheduled runs or manual full-matrix runs ("C# Matrix Tests") that ended in failure
+        if: github.event.workflow_run.conclusion == 'failure' && (github.event.workflow_run.event == 'schedule' || github.event.workflow_run.display_title == 'C# Matrix Tests')
+        runs-on: ubuntu-latest
+        steps:
+            - name: Download artifacts from triggering run
+              uses: dawidd6/action-download-artifact@v6
+              with:
+                  run_id: ${{ github.event.workflow_run.id }}
+                  path: downloaded
+
+            - name: Aggregate failures
+              id: aggregate
+              shell: bash
+              run: |
+                  set -euo pipefail
+                  if ! command -v jq >/dev/null 2>&1; then
+                    sudo apt-get update -y >/dev/null 2>&1 || true
+                    sudo apt-get install -y jq >/dev/null 2>&1 || true
+                  fi
+                  shopt -s globstar nullglob
+                  total_failed=0
+                  total_suites=0
+                  md='<!-- run:${{ github.event.workflow_run.id }} -->\n'
+                  md+="# Nightly CI failures for ${{ github.repository }}\n\n"
+                  md+="Triggered: ${{ github.event.workflow_run.run_started_at }} • [Run link](${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.event.workflow_run.id }})\n\n"
+                  found_any=0
+                  for f in downloaded/**/failures.json; do
+                    found_any=1
+                    failed=$(jq -r '.summary.failed // 0' "$f" 2>/dev/null || echo 0)
+                    total=$(jq -r '.summary.total // 0' "$f" 2>/dev/null || echo 0)
+                    job=$(jq -r '.jobName // empty' "$f" 2>/dev/null || echo "")
+                    [ -z "$job" ] && job=$(basename "$(dirname "$f")")
+                    runUrl=$(jq -r '.links.runUrl // empty' "$f" 2>/dev/null || echo "")
+                    total_failed=$((total_failed+failed))
+                    total_suites=$((total_suites+1))
+                    md+="- ${job}: ${failed}/${total} failed"
+                    if [ -n "$runUrl" ]; then
+                      md+=" — [run](${runUrl})"
+                    fi
+                    md+="\n"
+                  done
+                  if [ $found_any -eq 0 ]; then
+                    md+="No failures.json artifacts were found to summarize.\n"
+                  else
+                    md+="\nTotal failed tests across ${total_suites} matrix jobs: ${total_failed}\n"
+                  fi
+                  printf "%b" "$md" > summary.md
+                  echo "summary_path=$(pwd)/summary.md" >> "$GITHUB_OUTPUT"
+                  echo "total_failed=${total_failed}" >> "$GITHUB_OUTPUT"
+
+            - name: Find or create rolling failure issue
+              id: ensure_issue
+              uses: actions/github-script@v7
+              env:
+                  SUMMARY_PATH: ${{ steps.aggregate.outputs.summary_path }}
+              with:
+                  github-token: ${{ secrets.GITHUB_TOKEN }}
+                  script: |
+                      const fs = require('fs');
+                      const body = fs.readFileSync(process.env.SUMMARY_PATH, 'utf8');
+                      const marker = '<!-- run:${{ github.event.workflow_run.id }} -->';
+                      const {owner, repo} = context.repo;
+                      const label = 'ci-failure';
+                      const title = 'Nightly CI failures: C# tests';
+
+                      // Ensure label exists? Assume it's created manually as per repo policy.
+                      const {data: issues} = await github.rest.issues.listForRepo({
+                        owner, repo, state: 'open', labels: label, per_page: 100
+                      });
+                      let issue = issues.find(i => i.title === title);
+
+                      if (!issue) {
+                        const created = await github.rest.issues.create({
+                          owner, repo, title, body, labels: [label]
+                        });
+                        core.setOutput('issue_number', String(created.data.number));
+                        core.info(`Created issue #${created.data.number}`);
+                        return;
+                      }
+
+                      // Avoid duplicate comments for the same run using marker
+                      const {data: comments} = await github.rest.issues.listComments({
+                        owner, repo, issue_number: issue.number, per_page: 100
+                      });
+                      const exists = comments.some(c => c.body && c.body.includes(marker));
+                      if (!exists) {
+                        await github.rest.issues.createComment({
+                          owner, repo, issue_number: issue.number, body
+                        });
+                        core.info(`Commented on issue #${issue.number}`);
+                      } else {
+                        core.info('A comment for this run already exists; skipping.');
+                      }
+                      core.setOutput('issue_number', String(issue.number));