ping maintainers in case a PR was not properly labeled (#3993)

* test label extraction

* debug

* debug

* ping maintainers in case a PR was not properly labeled

* flake8

* add required labels

.github/process_pr.py

+import json
+import sys
+from typing import Any, Dict, Set, Tuple
+
+import requests
+
+# If the PR has any of these labels, we mark it as properly labeled.
+REQUIRED_LABELS = {
+    "new feature",
+    "bug",
+    "code quality",
+    "enhancement",
+    "bc-breaking",
+    "dependency issue",
+    "deprecation",
+    "module: c++ frontend",
+    "module: ci",
+    "module: datasets",
+    "module: documentation",
+    "module: io",
+    "module: models.quantization",
+    "module: models",
+    "module: onnx",
+    "module: ops",
+    "module: reference scripts",
+    "module: rocm",
+    "module: tests",
+    "module: transforms",
+    "module: utils",
+    "module: video",
+    "Perf",
+    "Revert(ed)",
+}
+
+
+def main(commit_hash: str) -> Dict[str, Any]:
+    pr_number = get_pr_number(commit_hash)
+    merger, labels = get_pr_merger_and_labels(pr_number)
+    is_properly_labeled = bool(REQUIRED_LABELS.intersection(labels))
+    if not is_properly_labeled:
+        users = {merger, *get_pr_reviewers(pr_number)}
+    else:
+        users = ()
+    return dict(
+        is_properly_labeled=is_properly_labeled,
+        responsible_users=", ".join(sorted([f"@{user}" for user in users])),
+    )
+
+
+def _query_torchvision(cmd: str, *, accept) -> Any:
+    response = requests.get(f"https://api.github.com/repos/pytorch/vision/{cmd}", headers=dict(Accept=accept))
+    return response.json()
+
+
+def get_pr_number(commit_hash: str) -> int:
+    # See https://docs.github.com/en/rest/reference/repos#list-pull-requests-associated-with-a-commit
+    data = _query_torchvision(f"commits/{commit_hash}/pulls", accept="application/vnd.github.groot-preview+json")
+    return data[0]["number"]
+
+
+def get_pr_merger_and_labels(pr_number: int) -> Tuple[str, Set[str]]:
+    # See https://docs.github.com/en/rest/reference/pulls#get-a-pull-request
+    data = _query_torchvision(f"pulls/{pr_number}", accept="application/vnd.github.v3+json")
+    merger = data["merged_by"]["login"]
+    labels = {label["name"] for label in data["labels"]}
+    return merger, labels
+
+
+def get_pr_reviewers(pr_number: int) -> Set[str]:
+    # See https://docs.github.com/en/rest/reference/pulls#list-reviews-for-a-pull-request
+    data = _query_torchvision(f"pulls/{pr_number}/reviews", accept="application/vnd.github.v3+json")
+    return {review["user"]["login"] for review in data if review["state"] == "APPROVED"}
+
+
+if __name__ == "__main__":
+    commit_hash = sys.argv[1]
+    data = main(commit_hash)
+    print(json.dumps(data))

.github/workflows/pr-labels.yml

+name: pr-labels
+
+on:
+  push:
+    branches:
+      - master
+
+jobs:
+  is-properly-labeled:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Set up python
+        uses: actions/setup-python@v2
+
+      - name: Install requests
+        run: pip install requests
+
+      - name: Checkout repository
+        uses: actions/checkout@v2
+
+      - name: Process PR associated with current commit
+        id: data
+        run: |
+          DATA=$(python .github/foo.py ${{ github.sha }})
+          jq . <<< $DATA
+          echo "::set-output name=is_properly_labeled::$(jq .is_properly_labeled <<< $DATA)"
+          echo "::set-output name=responsible_users::$(jq .responsible_users <<< $DATA)"
+
+      - name: Ping responsible users
+        if: steps.data.outputs.is_properly_labeled == "false"
+        uses: mshick/add-pr-comment@v1
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          message: |
+            Hey ${{ steps.data.outputs.responsible_users }}!
+
+            You approved or merged this PR, but no labels were added.