[GitHub] Add workflow to check author's commit access on new PRs

This workflow will run on every opened PR and add a label if the
author does not have the required permissions to merge their own
PR.

The permission check is based on code from #81142,
which tried to do this when a review was approved. That had to be
reverted in #81722 because
the event that it was triggered by did not have permissions to write
to the PR.

So we have a slight disadvantage that a label could be wrong by
the time the review is approved but ok, the author can click
the button themselves then anyway.

Plus, you could search by the label to find anything waiting
for someone to merge on behalf.

Author: DavidSpickett

.github/workflows/new-prs.yml

@@ -73,3 +73,31 @@ jobs:
           # workaround for https://github.com/actions/labeler/issues/112
           sync-labels: ''
           repo-token: ${{ secrets.ISSUE_SUBSCRIBER_TOKEN }}
+
+  check-commit-access:
+      runs-on: ubuntu-latest
+      permissions:
+        pull-requests: write
+      if: >-
+        (github.repository == 'llvm/llvm-project') &&
+        (github.event.action == 'opened')
+      steps:
+        - name: Checkout Automation Script
+          uses: actions/checkout@v4
+          with:
+            sparse-checkout: llvm/utils/git/
+            ref: main
+
+        - name: Setup Automation Script
+          working-directory: ./llvm/utils/git/
+          run: |
+            pip install --require-hashes -r requirements.txt
+
+        - name: Check Commit Access
+          working-directory: ./llvm/utils/git/
+          run: |
+            python3 ./github-automation.py \
+              --token '${{ secrets.GITHUB_TOKEN }}' \
+              check-commit-access \
+              --issue-number "${{ github.event.pull_request.number }}" \
+              --author "${{ github.event.pull_request.user.login }}"

llvm/utils/git/github-automation.py

@@ -290,6 +290,33 @@ def run(self) -> bool:
         return True
 
 
+class CheckCommitAccess:
+    def __init__(
+        self, token: str, repo: str, pr_number: int, author: str):
+        self.repo = github.Github(token).get_repo(repo)
+        self.pr = self.repo.get_issue(pr_number).as_pull_request()
+        self.author = author
+
+    def can_merge(self, user: str) -> bool:
+        try:
+            return self.repo.get_collaborator_permission(user) in ["admin", "write"]
+        # There is a UnknownObjectException for this scenario, but this method
+        # does not use it.
+        except github.GithubException as e:
+            # 404 means the author was not found in the collaborator list, so we
+            # know they don't have push permissions. Anything else is a real API
+            # issue, raise it so it is visible.
+            if e.status != 404:
+                raise e
+            return False
+
+    def run(self) -> bool:
+        if not self.can_merge(self.author):
+            self.pr.as_issue().add_to_labels("no-commit-access")
+
+        return True
+
+
 def setup_llvmbot_git(git_dir="."):
     """
     Configure the git repo in `git_dir` with the llvmbot account so
@@ -680,6 +707,10 @@ def request_release_note(token: str, repo_name: str, pr_number: int):
 pr_buildbot_information_parser.add_argument("--issue-number", type=int, required=True)
 pr_buildbot_information_parser.add_argument("--author", type=str, required=True)
 
+check_commit_access_parser = subparsers.add_parser("check-commit-access")
+check_commit_access_parser.add_argument("--issue-number", type=int, required=True)
+check_commit_access_parser.add_argument("--author", type=str, required=True)
+
 release_workflow_parser = subparsers.add_parser("release-workflow")
 release_workflow_parser.add_argument(
     "--llvm-project-dir",
@@ -751,6 +782,11 @@ def request_release_note(token: str, repo_name: str, pr_number: int):
         args.token, args.repo, args.issue_number, args.author
     )
     pr_buildbot_information.run()
+elif args.command == "check-commit-access":
+    check_commit_access = CheckCommitAccess(
+        args.token, args.repo, args.issue_number, args.author
+    )
+    check_commit_access.run()
 elif args.command == "release-workflow":
     release_workflow = ReleaseWorkflow(
         args.token,