Add workflow to post a comment on stale PRs

.github/workflows/ping_stale_prs.yml

@@ -0,0 +1,66 @@
+name: Ping Stale PRs
+
+# Posts comments on PRs that haven't had any interaction for more than a given number of weeks.
+#
+# The workflow tries to be smart and infer whether it's the PR author's turn to move the PR forward or if it is blocked
+# on actions by the reviewers and ping them accordingly.concurrency:
+#
+# Example usage in a repository:
+#
+# ```
+# name: Ping stale PRs
+# permissions:
+#   contents: read
+# on:
+#   schedule:
+#     - cron: '0 9 * * *'
+#   workflow_dispatch:
+# jobs:
+#   ping_stale_prs:
+#     name: Ping stale PRs
+#     uses: swiftlang/github-workflows/.github/workflows/ping_stale_prs.yml@main
+#     permissions:
+#       contents: write
+#       pull-requests: write
+#     if: (github.event_name == 'schedule' && github.repository == 'swiftlang/swift-format') || (github.event_name != 'schedule')  # Ensure that we don't run this on a schedule in a fork
+# ```
+
+
+permissions:
+  contents: read
+
+on:
+  workflow_call:
+    inputs:
+      stale_duration_weeks:
+        type: string
+        description: "The number of weeks after which a PR should be considered stale."
+        default: "4"
+
+jobs:
+  ping_stale_prs:
+    name: Ping Stale PRs
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    permissions:
+      pull-requests: write
+    steps:
+      - name: Checkout swiftlang/github-workflows repository
+        if: ${{ github.repository != 'swiftlang/github-workflows' }}
+        uses: actions/checkout@v4
+        with:
+          repository: swiftlang/github-workflows
+          path: github-workflows
+      - name: Determine script-root path
+        id: script_path
+        run: |
+          if [ "${{ github.repository }}" = "swiftlang/github-workflows" ]; then
+            echo "root=$GITHUB_WORKSPACE" >> $GITHUB_OUTPUT
+          else
+            echo "root=$GITHUB_WORKSPACE/github-workflows" >> $GITHUB_OUTPUT
+          fi
+      - name: Post comment on stale PRs
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: |
+          python3 ${{ steps.script_path.outputs.root }}/.github/workflows/scripts/ping_stale_prs.py --stale-duration ${{ inputs.stale_duration_weeks }} --repo ${{ github.repository }}

.github/workflows/scripts/ping_stale_prs.py

@@ -0,0 +1,155 @@
+#!/usr/bin/env python3
+##===----------------------------------------------------------------------===##
+##
+## This source file is part of the Swift.org open source project
+##
+## Copyright (c) 2026 Apple Inc. and the Swift project authors
+## Licensed under Apache License v2.0 with Runtime Library Exception
+##
+## See https://swift.org/LICENSE.txt for license information
+## See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+##
+##===----------------------------------------------------------------------===##
+
+import argparse
+import json
+import subprocess
+from datetime import datetime, timedelta, timezone
+
+argparse = argparse.ArgumentParser()
+argparse.add_argument(
+    "--stale-duration",
+    required=True,
+    help="Number of weeks after which a PR is considered stale"
+)
+argparse.add_argument(
+    "--repo",
+    required=True,
+    help="Repo in which to check for stale PRs, eg. swiftlang/swift-syntax"
+)
+argparse.add_argument(
+    "--dry-run",
+    action="store_true",
+    help="Repo in which to check for stale PRs, eg. swiftlang/swift-syntax"
+)
+args = argparse.parse_args()
+
+stale_duration_weeks = int(args.stale_duration)
+repo = str(args.repo)
+dry_run = bool(args.dry_run)
+
+stale_date = datetime.now(timezone.utc) - timedelta(weeks=stale_duration_weeks)
+
+command = [
+    "gh", "pr", "list", "-R", repo, "--search",
+    f"updated:<{stale_date.isoformat()} draft:false is:pr is:open",
+    "--json", "author,comments,commits,number,reviewDecision,reviewRequests,reviews,url"
+]
+prs = json.loads(subprocess.check_output(command, encoding="utf-8"))
+
+distant_past = datetime.fromtimestamp(0, timezone.utc)
+
+
+def user_has_write_access(user: str) -> bool:
+    output = subprocess.check_output(
+        ["gh", "api", f"repos/{repo}/collaborators/{user}/permission"],
+        encoding="utf-8"
+    )
+    return json.loads(output)["permission"] in ["write", "push", "admin"]
+
+
+def print_command(command: list[str]) -> None:
+    print(" ".join([f"'{arg}'" if " " in arg else arg for arg in command]))
+
+
+for pr in prs:
+    pr_author = pr["author"]["login"]
+
+    # Filter out reviews from users who aren't affiliated with the repository
+    relevant_reviews = [
+        review for review in pr["reviews"]
+        if review["authorAssociation"] in ["COLLABORATOR", "MEMBER", "OWNER"]
+    ]
+    reviewers = [review_request["login"] for review_request in pr["reviewRequests"]]
+    reviewers.extend([review["author"]["login"] for review in relevant_reviews])
+
+    reviewer_interaction_dates: list[str] = []
+    reviewer_interaction_dates.extend(
+        [review["submittedAt"] for review in relevant_reviews]
+    )
+    reviewer_interaction_dates.extend([
+        comment["createdAt"] for comment in pr["comments"]
+        if comment["author"]["login"] in reviewers
+        if "@swift-ci" not in comment["body"]
+    ])
+
+    author_interaction_dates: list[str] = []
+    author_interaction_dates.extend(
+        [commit["authoredDate"] for commit in pr["commits"]]
+    )
+    author_interaction_dates.extend(
+        [commit["committedDate"] for commit in pr["commits"]]
+    )
+    author_interaction_dates.extend([
+        comment["createdAt"] for comment in pr["comments"]
+        if comment["author"]["login"] == pr_author
+        if "@swift-ci" not in comment["body"]
+    ])
+
+    if reviewer_interaction_dates:
+        last_reviewer_interaction_date = datetime.fromisoformat(
+            max(reviewer_interaction_dates).replace("Z", "+00:00")
+        )
+    else:
+        last_reviewer_interaction_date = distant_past
+
+    if author_interaction_dates:
+        last_author_interaction_date = datetime.fromisoformat(
+            max(author_interaction_dates).replace("Z", "+00:00")
+        )
+    else:
+        last_author_interaction_date = distant_past
+
+    comment = f"This PR has not been modified for {stale_duration_weeks} weeks. "
+    reviewers.sort()
+    joined_reviewers = ", ".join(["@" + r for r in reviewers])
+    reviewers_ping = joined_reviewers or "Code Owners of this repository"
+    if pr["reviewDecision"] == "APPROVED":
+        if user_has_write_access(pr_author):
+            comment += (
+                f"{pr_author} given this PR has an approving review, "
+                "please try and merge the PR. Should the PR be no longer "
+                "relevant, please close it. Should you take more time to "
+                "work on it, please mark it as draft to disable these "
+                "notifications.."
+            )
+        else:
+            comment += (
+                f"{reviewers_ping} given this PR has an approving review "
+                "but the author does not have merge access, please help "
+                "the author to make the PR pass CI checks and get it "
+                "merged."
+            )
+    elif last_author_interaction_date < last_reviewer_interaction_date:
+        comment += (
+            f"@{pr_author} to help move this PR forward, please address "
+            "the review feedback. Should the PR be no longer relevant, "
+            "please close it. Should you take more time to work on it, "
+            "please mark it as draft to disable these notifications."
+        )
+    else:
+        comment += (
+            f"{reviewers_ping} to help move this PR forward, "
+            "please review it."
+        )
+
+    add_comment_command = [
+        "gh", "pr",
+        "-R", repo,
+        "comment", str(pr["number"]),
+        "--body", comment
+    ]
+    if dry_run:
+        print_command(add_comment_command)
+    else:
+        subprocess.check_call(add_comment_command)