[Infra] Replace Danger with Python script for changelog checks (#8470)

Replace the Ruby-based Danger changelog verification setup with a custom
Python script (`ci/changelog_check.py`).

* Update: `.github/workflows/changelog.yml` to run
`actions/setup-python` with Python 3.12 instead of Ruby setup and
Bundler steps.
* Grant: `pull-requests: write` and `issues: write` permissions in the
GitHub Actions workflow to enable PR comment management.
* Add: `ci/changelog_check.py` to check for changelog updates when SDK
source files are modified, with support for PR comments via the GitHub
API and skipping options (`no-changelog` label or `NO_RELEASE_CHANGE`
description).
* Remove: Danger files including `Dangerfile`, `Gemfile`,
`Gemfile.lock`, and `setup_bundler.sh`.

---------

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Author: rlazo

.github/workflows/changelog.yml

@@ -9,25 +9,22 @@ concurrency:
 
 permissions:
   contents: read
+  pull-requests: write
+  issues: write
 
 jobs:
   changelog-check:
     runs-on: ubuntu-22.04
-    env:
-      BUNDLE_GEMFILE: ./ci/danger/Gemfile
     steps:
     - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
       with:
         fetch-depth: 100
         submodules: true
         persist-credentials: false
-    - uses: ruby/setup-ruby@12fd324f1d0b43274fdc8130f6980590a667c455 # v1.312.0
+    - uses: actions/setup-python@a309ff8b426b58ec0e2a45f0f869d46889d02405 # v6.2.0
       with:
-        ruby-version: '3.4'
-    - name: Setup Bundler
-      run: ./ci/danger/setup_bundler.sh
-    - name: Danger CHANGELOG verifier
+        python-version: '3.12'
+    - name: Verify CHANGELOG update
       env:
-        DANGER_GITHUB_API_TOKEN: ${{ secrets.GOOGLE_OSS_BOT_TOKEN }}
-      run:
-        '[ ! -z $DANGER_GITHUB_API_TOKEN ] && bundle exec danger --dangerfile=./ci/danger/Dangerfile || echo "Skipping Danger for External Contributor"'
+        GITHUB_TOKEN: ${{ secrets.GOOGLE_OSS_BOT_TOKEN || secrets.GITHUB_TOKEN }}
+      run: python3 ci/changelog_check.py

ci/changelog_check.py

@@ -0,0 +1,291 @@
+#!/usr/bin/env python3
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import os
+import sys
+import subprocess
+import json
+import re
+import urllib.request
+
+# Ignore changes in these directories
+EXCLUDE_DIRECTORIES = [
+  '.github/',
+  'plugins/',
+  'ci/',
+  'encoders/',
+  'firebase-annotations/',
+  'firebase-components/',
+  'firebase-datatransport/',
+  'gradle/',
+  'health-metrics/',
+  'integ-testing/',
+  'protolite-well-known-types/',
+  'smoke-tests/',
+  'third_party/',
+  'tools/',
+  'transport/'
+]
+
+SIGNATURE = "<!-- python-changelog-warning -->"
+
+def should_file_be_excluded(file, exclude_paths):
+    return any(dir_path in file for dir_path in exclude_paths)
+
+def has_changes_in(paths, modified_files):
+    for path in paths:
+        regex = re.compile(path)
+        if any(regex.search(file) for file in modified_files):
+            return True
+    return False
+
+def has_sdk_changes(modified_files):
+    return any(not should_file_be_excluded(f, EXCLUDE_DIRECTORIES) for f in modified_files)
+
+def get_modified_files():
+    # If running in GitHub Actions, try to use the GitHub API to avoid shallow clone issues
+    repo = os.environ.get('GITHUB_REPOSITORY')
+    token = os.environ.get('GITHUB_TOKEN')
+    event_path = os.environ.get('GITHUB_EVENT_PATH')
+    if repo and token and event_path:
+        try:
+            with open(event_path, 'r') as f:
+                event_data = json.load(f)
+                pull_request = event_data.get('pull_request')
+                if pull_request:
+                    pr_number = pull_request.get('number')
+                    headers = {
+                        "Authorization": f"token {token}",
+                        "Accept": "application/vnd.github.v3+json",
+                        "User-Agent": "Python-urllib"
+                    }
+                    files = []
+                    page = 1
+                    while True:
+                        url = f"https://api.github.com/repos/{repo}/pulls/{pr_number}/files?per_page=100&page={page}"
+                        req = urllib.request.Request(url, headers=headers)
+                        with urllib.request.urlopen(req) as response:
+                            page_files = json.loads(response.read().decode('utf-8'))
+                            if not page_files:
+                                break
+                            files.extend([f['filename'] for f in page_files])
+                            if len(page_files) < 100:
+                                break
+                            page += 1
+                    return files
+        except Exception as e:
+            print(f"Warning: Failed to fetch modified files via GitHub API: {e}", file=sys.stderr)
+            print("Falling back to git diff...", file=sys.stderr)
+
+    print("Attempting fallback to diff against origin/main", file=sys.stderr)
+    # Fallback for local testing or different checkout configurations
+    for base in ['origin/main', 'main']:
+        try:
+            result = subprocess.run(
+                ['git', 'diff', '--name-only', f'{base}...HEAD'],
+                stdout=subprocess.PIPE,
+                stderr=subprocess.PIPE,
+                text=True,
+                check=True
+            )
+            files = result.stdout.strip().split('\n')
+            return [f for f in files if f]
+        except subprocess.CalledProcessError:
+            continue
+    return []
+
+
+def get_modified_files():
+    try:
+        # Compare HEAD with its first parent.
+        # In GitHub Actions pull_request event, HEAD is the merge commit,
+        # and HEAD^1 is the base branch (target of PR).
+        result = subprocess.run(
+            ['git', 'diff', '--name-only', 'HEAD^1'],
+            stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE,
+            text=True,
+            check=True
+        )
+        files = result.stdout.strip().split('\n')
+        return [f for f in files if f]
+    except subprocess.CalledProcessError as e:
+        print(f"Warning: git diff HEAD^1 failed: {e.stderr.strip()}", file=sys.stderr)
+        print("Attempting fallback to diff against origin/main", file=sys.stderr)
+        # Fallback for local testing or different checkout configurations
+        for base in ['origin/main', 'origin/master', 'main', 'master']:
+            try:
+                result = subprocess.run(
+                    ['git', 'diff', '--name-only', f'{base}...HEAD'],
+                    stdout=subprocess.PIPE,
+                    stderr=subprocess.PIPE,
+                    text=True,
+                    check=True
+                )
+                files = result.stdout.strip().split('\n')
+                return [f for f in files if f]
+            except subprocess.CalledProcessError:
+                continue
+        print("Error: Could not determine modified files via git.", file=sys.stderr)
+        return []
+
+def get_pr_details():
+    event_path = os.environ.get('GITHUB_EVENT_PATH')
+    if not event_path:
+        print("GITHUB_EVENT_PATH not set. Running in non-CI mode?", file=sys.stderr)
+        return None, [], ""
+
+    try:
+        with open(event_path, 'r') as f:
+            event_data = json.load(f)
+            pull_request = event_data.get('pull_request')
+            if pull_request:
+                pr_number = pull_request.get('number')
+                labels = [l['name'] for l in pull_request.get('labels', [])]
+                body = pull_request.get('body') or ""
+                return pr_number, labels, body
+            else:
+                print("Event is not a pull request.", file=sys.stderr)
+                return None, [], ""
+    except Exception as e:
+        print(f"Error reading GITHUB_EVENT_PATH: {e}", file=sys.stderr)
+        return None, [], ""
+
+def get_pr_comments(repo, pr_number, headers):
+    comments = []
+    page = 1
+    while True:
+        url = f"https://api.github.com/repos/{repo}/issues/{pr_number}/comments?per_page=100&page={page}"
+        req = urllib.request.Request(url, headers=headers)
+        try:
+            with urllib.request.urlopen(req) as response:
+                page_comments = json.loads(response.read().decode('utf-8'))
+                if not page_comments:
+                    break
+                comments.extend(page_comments)
+                if len(page_comments) < 100:
+                    break
+                page += 1
+        except Exception as e:
+            print(f"Error fetching comments page {page}: {e}", file=sys.stderr)
+            break
+    return comments
+
+def post_or_update_comment(repo, pr_number, token, message):
+    comments_url = f"https://api.github.com/repos/{repo}/issues/{pr_number}/comments"
+    headers = {
+        "Authorization": f"token {token}",
+        "Accept": "application/vnd.github.v3+json",
+        "User-Agent": "Python-urllib"
+    }
+
+    comments = get_pr_comments(repo, pr_number, headers)
+
+    existing_comment = None
+    for comment in comments:
+        if SIGNATURE in comment.get('body', ''):
+            existing_comment = comment
+            break
+
+    body = f"{message}\n{SIGNATURE}"
+    data = json.dumps({"body": body}).encode('utf-8')
+
+    if existing_comment:
+        comment_id = existing_comment['id']
+        # If the message is the same, do nothing
+        if existing_comment.get('body') == body:
+            print(f"Comment {comment_id} is up to date.")
+            return
+
+        update_url = f"https://api.github.com/repos/{repo}/issues/comments/{comment_id}"
+        req = urllib.request.Request(update_url, data=data, headers=headers, method='PATCH')
+        action = f"updating existing comment {comment_id}"
+    else:
+        req = urllib.request.Request(comments_url, data=data, headers=headers, method='POST')
+        action = "creating new comment"
+
+    print(f"Action: {action}")
+    try:
+        with urllib.request.urlopen(req) as response:
+            print("Comment posted/updated successfully.")
+    except Exception as e:
+        print(f"Error posting/updating comment: {e}", file=sys.stderr)
+
+def delete_comment_if_exists(repo, pr_number, token):
+    headers = {
+        "Authorization": f"token {token}",
+        "Accept": "application/vnd.github.v3+json",
+        "User-Agent": "Python-urllib"
+    }
+
+    comments = get_pr_comments(repo, pr_number, headers)
+
+    for comment in comments:
+        if SIGNATURE in comment.get('body', ''):
+            comment_id = comment['id']
+            delete_url = f"https://api.github.com/repos/{repo}/issues/comments/{comment_id}"
+            req = urllib.request.Request(delete_url, headers=headers, method='DELETE')
+            try:
+                with urllib.request.urlopen(req) as response:
+                    print(f"Deleted existing comment {comment_id}")
+            except Exception as e:
+                print(f"Error deleting comment: {e}", file=sys.stderr)
+
+
+def main():
+    modified_files = get_modified_files()
+    print(f"Modified files: {modified_files}")
+
+    pr_number, labels, body = get_pr_details()
+    print(f"PR number: {pr_number}, Labels: {labels}")
+    if body:
+        print(f"PR body preview: {body[:100]}...")
+    else:
+        print("PR body is empty or not available.")
+
+    declared_trivial = "no-changelog" in labels or "NO_RELEASE_CHANGE" in body
+    has_changelog_changes = has_changes_in(["CHANGELOG"], modified_files)
+    sdk_changes = has_sdk_changes(modified_files)
+
+    print(f"SDK changes: {sdk_changes}")
+    print(f"Changelog changes: {has_changelog_changes}")
+    print(f"Declared trivial: {declared_trivial}")
+
+    warning_needed = sdk_changes and not has_changelog_changes and not declared_trivial
+
+    token = os.environ.get('GITHUB_TOKEN')
+    repo = os.environ.get('GITHUB_REPOSITORY')
+
+    warning_message = (
+        "Did you forget to add a changelog entry? "
+        "(Add the 'no-changelog' label to the PR or 'NO_RELEASE_CHANGE' to the description to silence this warning.)"
+    )
+
+    if warning_needed:
+        print(f"WARNING: {warning_message}")
+        # Also output as GitHub Actions warning annotation
+        print(f"::warning::{warning_message}")
+
+        if token and repo and pr_number:
+            post_or_update_comment(repo, pr_number, token, warning_message)
+        else:
+            print("Missing token, repo, or PR number. Skipping PR comment.", file=sys.stderr)
+    else:
+        print("No warning needed.")
+        if token and repo and pr_number:
+            delete_comment_if_exists(repo, pr_number, token)
+
+if __name__ == "__main__":
+    main()