Merge pull request #10549 from Joe-Downs/pr/gh-actions-labeling

github-labeler: add label corresponding to the target branch

Author: jsquyres

.github/workflows/github-labeler.py

@@ -0,0 +1,59 @@
+#!/usr/bin/env python3
+
+"""
+
+The script applies a label in the form "Target: {branchName}. If necessary, it
+removes labels in the same form, but NOT for the target branch. For instance, if
+someone edited the target branch from v4.0.x to v5.0.x
+
+"""
+
+import os
+import re
+import sys
+
+from github import Github
+
+# ==============================================================================
+
+GITHUB_BASE_REF = os.environ.get('GITHUB_BASE_REF')
+GITHUB_TOKEN = os.environ.get('GITHUB_TOKEN')
+GITHUB_REPOSITORY = os.environ.get('GITHUB_REPOSITORY')
+PR_NUM = os.environ.get('PR_NUM')
+
+# Sanity check
+if (GITHUB_BASE_REF is None or
+    GITHUB_TOKEN is None or
+    GITHUB_REPOSITORY is None or
+    PR_NUM is None):
+    print("Error: this script is designed to run as a Github Action")
+    exit(1)
+
+# ==============================================================================
+
+# Given a pullRequest object, the function checks what labels are currently on
+# the pull request, removes any matching the form "Target: {branch}" (if
+# {branch} is not the current target branch), and adds the correct label.
+def ensureLabels(pullRequest):
+    needsLabel = True
+    targetPrefix = "Target: "
+    targetLabel = f"{targetPrefix}{GITHUB_BASE_REF}"
+    for label in pullRequest.get_labels():
+        if label.name.startswith(targetPrefix):
+            if label.name == targetLabel:
+                needsLabel = False
+            else:
+                print(f"Removing label '{label.name}")
+                pullRequest.remove_from_labels(label)
+    if needsLabel:
+        print(f"Adding label '{targetLabel}")
+        pullRequest.add_to_labels(targetLabel)
+    return None
+
+# ==============================================================================
+
+g = Github(GITHUB_TOKEN)
+repo = g.get_repo(GITHUB_REPOSITORY)
+prNum = int(PR_NUM)
+pr = repo.get_pull(prNum)
+ensureLabels(pr)

.github/workflows/github-labeler.yaml

@@ -0,0 +1,36 @@
+name: GitHub Action Labeler
+
+# We're using pull_request_target here instead of just pull_request so that the
+# action runs in the context of the base of the pull request, rather than in the
+# context of the merge commit. For more detail about the differences, see:
+# https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#pull_request_target
+on:
+    pull_request_target:
+        # We don't need this to be run on all types of PR behavior
+        # See https://docs.github.com/en/actions/reference/events-that-trigger-workflows#pull_request
+        # You can change the base branch, so update the label if it's edited.
+        types:
+          - opened
+          - edited
+
+jobs:
+    ci:
+        name: Label Bot
+        runs-on: ubuntu-latest
+        steps:
+          - name: Check out the code
+            uses: actions/checkout@v2
+
+          - name: Setup Python
+            uses: actions/setup-python@v2
+            with:
+              python-version: '3.x'
+
+          - name: Get the PyGithub module
+            run: pip install PyGithub
+
+          - name: Label the PR (if needed)
+            run: $GITHUB_WORKSPACE/.github/workflows/github-labeler.py
+            env:
+                GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+                PR_NUM: ${{ github.event.number }}