feat(workflows): add closed-PR comment redirect

.github/workflows/github-slack-notifications.yml

@@ -0,0 +1,220 @@
+name: GitHub Slack Notifications
+
+# Central GitHub -> Slack integration point. Two triggers feed one shared
+# Slack workflow (via SLACK_WEBHOOK_URL), which branches on event_type:
+#   - issues opened           -> notify oncall of a new issue
+#   - comments on closed PRs  -> redirect the commenter to open an issue,
+#                                and notify oncall (closed-PR comments are
+#                                otherwise easy to miss)
+# Every payload sends the same key set so the Slack workflow can branch
+# reliably; fields that don't apply to an event are sent empty.
+
+on:
+  issues:
+    types: [opened]
+  issue_comment:
+    types: [created]
+
+jobs:
+  notify-issue-opened:
+    if: github.event_name == 'issues'
+    runs-on: ubuntu-latest
+    permissions: {}
+    steps:
+      - name: Send issue details to Slack
+        # Attacker-controlled fields are passed through env: rather than
+        # interpolated into the YAML payload, to prevent workflow injection.
+        # For issue_opened, the issue_* fields carry the data and the
+        # pr_*/comment_* fields are empty.
+        env:
+          REPOSITORY: ${{ github.repository }}
+          CREATED_AT: ${{ github.event.issue.created_at }}
+          ISSUE_NUMBER: ${{ github.event.issue.number }}
+          ISSUE_TITLE: ${{ github.event.issue.title }}
+          ISSUE_URL: ${{ github.event.issue.html_url }}
+          ISSUE_AUTHOR: ${{ github.event.issue.user.login }}
+          ISSUE_BODY: ${{ github.event.issue.body }}
+          LABELS: ${{ join(github.event.issue.labels.*.name, ', ') }}
+        uses: slackapi/slack-github-action@v3.0.1
+        with:
+          webhook: ${{ secrets.SLACK_WEBHOOK_URL }}
+          webhook-type: webhook-trigger
+          payload: |
+            event_type: "issue_opened"
+            repository: "${{ env.REPOSITORY }}"
+            created_at: "${{ env.CREATED_AT }}"
+            issue_number: "${{ env.ISSUE_NUMBER }}"
+            issue_title: ${{ toJSON(env.ISSUE_TITLE) }}
+            issue_url: "${{ env.ISSUE_URL }}"
+            issue_author: "${{ env.ISSUE_AUTHOR }}"
+            issue_body: ${{ toJSON(env.ISSUE_BODY) }}
+            labels: ${{ toJSON(env.LABELS) }}
+            pr_number: ""
+            pr_title: ""
+            pr_url: ""
+            pr_author: ""
+            pr_state: ""
+            pr_closed_at: ""
+            pr_merged_at: ""
+            comment_id: ""
+            comment_url: ""
+            comment_author: ""
+            comment_body: ""
+
+  closed-pr-comment-redirect:
+    # Only fire on comments left on PRs (issue_comment fires for issues too)
+    # that are already closed, and skip comments left by bots.
+    if: >-
+      github.event_name == 'issue_comment' && github.event.issue.pull_request != null && github.event.issue.state ==
+      'closed' && github.event.comment.user.type != 'Bot'
+    runs-on: ubuntu-latest
+    permissions:
+      pull-requests: write
+      issues: read
+    # Serialize per-PR so the marker-comment dedup is race-free (otherwise two
+    # rapid-fire comments could both see "no marker" and both post a redirect).
+    # cancel-in-progress is false so the second run still executes after the
+    # first finishes -- we want to evaluate dedup against the just-posted marker.
+    concurrency:
+      group: closed-pr-comment-${{ github.event.issue.number }}
+      cancel-in-progress: false
+    steps:
+      - name: Check commenter permission
+        id: perm
+        uses: actions/github-script@v9
+        with:
+          script: |
+            // External users on private repos can 404 here; treat any
+            // failure as "not a maintainer" so the redirect still fires.
+            let permission = 'none';
+            try {
+              const { data } = await github.rest.repos.getCollaboratorPermissionLevel({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                username: context.payload.comment.user.login,
+              });
+              permission = data.permission;
+            } catch (err) {
+              core.info(`Permission lookup failed for ${context.payload.comment.user.login}: ${err.message}. Treating as non-maintainer.`);
+            }
+            const skip = ['admin', 'maintain', 'write'].includes(permission);
+            core.setOutput('skip', String(skip));
+            core.info(`Commenter ${context.payload.comment.user.login} permission=${permission} skip=${skip}`);
+
+      - name: Check for existing redirect comment
+        id: existing
+        if: steps.perm.outputs.skip != 'true'
+        uses: actions/github-script@v9
+        with:
+          script: |
+            // Marker we embed in our reply so we don't double-post on the same PR.
+            const marker = '<!-- closed-pr-comment-redirect -->';
+            const comments = await github.paginate(
+              github.rest.issues.listComments,
+              {
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                issue_number: context.payload.issue.number,
+                per_page: 100,
+              }
+            );
+            const alreadyPosted = comments.some(c => c.body && c.body.includes(marker));
+            core.setOutput('already_posted', String(alreadyPosted));
+
+      - name: Post redirect comment
+        if: steps.perm.outputs.skip != 'true' && steps.existing.outputs.already_posted != 'true'
+        # The Slack notification is the load-bearing part of this job. If
+        # posting the bot reply fails (rate limit, transient error), don't
+        # block the Slack notification.
+        continue-on-error: true
+        uses: actions/github-script@v9
+        env:
+          # Repos with issue templates use /issues/new/choose; repos without
+          # templates should change this to /issues/new.
+          ISSUES_NEW_URL: https://github.com/${{ github.repository }}/issues/new/choose
+        with:
+          script: |
+            const commenter = context.payload.comment.user.login;
+            const issuesNewUrl = process.env.ISSUES_NEW_URL;
+            const body = [
+              '<!-- closed-pr-comment-redirect -->',
+              '',
+              `Thanks for the report, @${commenter} — feedback like this is exactly`,
+              "how we catch the things we missed. Because this PR is already",
+              "closed, the team won't see follow-up comments here.",
+              '',
+              'Would you mind opening a new issue so we can track it properly?',
+              issuesNewUrl,
+              '',
+              'If this is a security issue, please report it privately via',
+              'https://aws.amazon.com/security/vulnerability-reporting/ instead',
+              'of a public issue.',
+            ].join('\n');
+
+            await github.rest.issues.createComment({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: context.payload.issue.number,
+              body,
+            });
+
+      - name: Compute PR state
+        id: pr_state
+        if: steps.perm.outputs.skip != 'true'
+        uses: actions/github-script@v9
+        with:
+          script: |
+            // PRs surface as `issue` events; merged_at is null when closed-not-merged.
+            const mergedAt = context.payload.issue.pull_request &&
+              context.payload.issue.pull_request.merged_at;
+            core.setOutput('state', mergedAt ? 'merged' : 'closed');
+
+      - name: Notify Slack
+        # Notify oncall only on the FIRST external comment per PR (gated by
+        # already_posted). Subsequent comments on the same PR don't notify --
+        # the redirect comment has already directed the commenter to open an
+        # issue, and issues notify oncall via the issue path. This bounds
+        # notification volume regardless of how chatty a thread becomes.
+        if: steps.perm.outputs.skip != 'true' && steps.existing.outputs.already_posted != 'true'
+        # Attacker-controlled fields are passed through env: rather than
+        # interpolated into the YAML payload, to prevent workflow injection.
+        # For closed-PR comments, the issue_* fields are empty (this isn't
+        # an issue) and the pr_*/comment_* fields carry the real data.
+        env:
+          REPOSITORY: ${{ github.repository }}
+          CREATED_AT: ${{ github.event.comment.created_at }}
+          PR_NUMBER: ${{ github.event.issue.number }}
+          PR_TITLE: ${{ github.event.issue.title }}
+          PR_URL: ${{ github.event.issue.html_url }}
+          PR_AUTHOR: ${{ github.event.issue.user.login }}
+          PR_CLOSED_AT: ${{ github.event.issue.closed_at }}
+          PR_MERGED_AT: ${{ github.event.issue.pull_request.merged_at }}
+          COMMENT_ID: ${{ github.event.comment.id }}
+          COMMENT_URL: ${{ github.event.comment.html_url }}
+          COMMENT_AUTHOR: ${{ github.event.comment.user.login }}
+          COMMENT_BODY: ${{ github.event.comment.body }}
+        uses: slackapi/slack-github-action@v3.0.1
+        with:
+          webhook: ${{ secrets.SLACK_WEBHOOK_URL }}
+          webhook-type: webhook-trigger
+          payload: |
+            event_type: "closed_pr_comment"
+            repository: "${{ env.REPOSITORY }}"
+            created_at: "${{ env.CREATED_AT }}"
+            issue_number: ""
+            issue_title: ""
+            issue_url: ""
+            issue_author: ""
+            issue_body: ""
+            labels: ""
+            pr_number: "${{ env.PR_NUMBER }}"
+            pr_title: ${{ toJSON(env.PR_TITLE) }}
+            pr_url: "${{ env.PR_URL }}"
+            pr_author: "${{ env.PR_AUTHOR }}"
+            pr_state: "${{ steps.pr_state.outputs.state }}"
+            pr_closed_at: "${{ env.PR_CLOSED_AT }}"
+            pr_merged_at: "${{ env.PR_MERGED_AT }}"
+            comment_id: "${{ env.COMMENT_ID }}"
+            comment_url: "${{ env.COMMENT_URL }}"
+            comment_author: "${{ env.COMMENT_AUTHOR }}"
+            comment_body: ${{ toJSON(env.COMMENT_BODY) }}