infra: Fix PR triage once and for all (#5442)

Switch to a custom made python script that query GitHub API to grab latest state of the PR after label assign.

.github/update_reviewers.py

@@ -0,0 +1,79 @@
+from pathlib import Path
+from typing import List, Set
+from github import Github
+from github.Repository import Repository
+from github.GithubException import GithubException
+
+import sys
+import yaml
+
+
+def add_reviewers(
+    reviewers: Set[str], team_reviewers: Set[str], new_entries: List[str]
+):
+    for reviewer in new_entries:
+        if reviewer.startswith("@"):
+            team_reviewers.add(reviewer[1:])
+        else:
+            reviewers.add(reviewer)
+
+
+def update_reviewers(config, repo: Repository, pr_id: int) -> int:
+    pull_request = repo.get_pull(pr_id)
+
+    if not pull_request:
+        sys.stderr.writable(f"Unknown PR #{pr_id}\n")
+        return 1
+
+    pull_request_author = pull_request.user.login
+    reviewers = set()
+    team_reviewers = set()
+
+    for label in pull_request.labels:
+        if label.name in config:
+            add_reviewers(reviewers, team_reviewers, config[label.name])
+
+    if "default" in config:
+        add_reviewers(reviewers, team_reviewers, config["default"])
+
+    if pull_request_author in reviewers:
+        reviewers.remove(pull_request_author)
+
+    try:
+        reviewers = list(reviewers)
+        team_reviewers = list(team_reviewers)
+        print(
+            f"Attempting to assign reviewers ({reviewers}) and team_reviewers ({team_reviewers})"
+        )
+        pull_request.create_review_request(reviewers, team_reviewers)
+        return 0
+    except GithubException as e:
+        sys.stderr.write(f"Cannot assign review request for PR #{pr_id}: {e}\n")
+        return 1
+
+
+if __name__ == "__main__":
+    if len(sys.argv) != 5:
+        sys.stderr.write("usage: <token> <repo_path> <pr_id> <config_path>\n")
+        sys.exit(1)
+
+    token = sys.argv[1]
+    repo_path = sys.argv[2]
+    pr_id = int(sys.argv[3])
+    config_path = Path(sys.argv[4])
+
+    g = Github(token)
+    repo = g.get_repo(repo_path)
+
+    if not repo:
+        sys.stderr.write("Repository not found!\n")
+        sys.exit(1)
+
+    if not config_path.exists():
+        sys.stderr.write(f'Config "{config_path}" not found!\n')
+        sys.exit(1)
+
+    with open(config_path, "r") as f:
+        config = yaml.safe_load(f)
+
+    sys.exit(update_reviewers(config, repo, pr_id))