Introduce tools/crates/create_draft_comments.py to streamline reviews.

The new script looks at all files touched by the current git branch and
for all occurrences of the `unsafe` keyword it automatically creates a
draft code review comment on Gerrit saying: "TODO: `unsafe` review".

Fixed: 328789397
Change-Id: I19c09a3453fd634b6f87e697a9e5eec211c8f9cc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5836753
Reviewed-by: danakj <danakj@chromium.org>
Commit-Queue: Łukasz Anforowicz <lukasza@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1352314}

docs/rust-unsafe.md

@@ -14,7 +14,8 @@ To facilitate a code review please:
 
 * For each new or modified `unsafe` block, function, `impl`, etc.,
   add an unresolved "TODO: `unsafe` review" comment in Gerrit.
-    - TODO(https://crbug.com/328789397): Automate this via Tricium or AyeAye.
+  You can consider using `tools/crates/create_draft_comments.py` to streamline
+  creating such comments.
 
 Note that changes _anywhere_ in a crate that uses `unsafe` blocks may violate
 the internal invariants on which those `unsafe` blocks rely. It is unrealistic

tools/crates/create_draft_comments.py

@@ -0,0 +1,96 @@
+#!/usr/bin/env vpython3
+# Copyright 2024 The Chromium Authors
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+"""
+This script can help with creating draft comments in a Gerrit code review.
+
+The script needs to be invoked from a `git` branch that 1) is associated
+with a Gerrit review, and 2) has an explicitly defined upstream branch.
+The script is typically invoked either on 1) an update branch created by
+`//tools/crates/create_update_cl.py`, or 2) a manually crated branch that adds a
+new crate to Chromium.
+"""
+
+import argparse
+import json
+import os
+import re
+import shutil
+import sys
+from create_update_cl import Git
+
+DEPOT_TOOLS_PATH = os.path.dirname(shutil.which('gclient'))
+sys.path.insert(0, DEPOT_TOOLS_PATH)
+from gerrit_util import CreateHttpConn, ReadHttpJsonResponse
+
+
+class DraftCreator:
+
+    def __init__(self):
+        gerrit_json = json.loads(Git('cl', 'issue', '--json=-').splitlines()[1])
+        self.gerrit_host = gerrit_json['gerrit_host']
+        self.gerrit_issue = str(gerrit_json['issue'])
+
+    def CreateDraft(self, path, line, message):
+        """ Calls the following REST API:
+        https://gerrit-review.googlesource.com/Documentation/rest-api-changes.html#create-draft
+        """
+
+        url_path = f'changes/{self.gerrit_issue}/revisions/current/drafts'
+        body: Dict[str, Any] = {
+            'path': str(path),
+            'line': int(line),
+            'message': message,
+            'unresolved': True,
+        }
+        print(f'Creating a comment for {path}:{line}')
+        conn = CreateHttpConn(self.gerrit_host,
+                              url_path,
+                              reqtype='PUT',
+                              body=body)
+        response = ReadHttpJsonResponse(conn, accept_statuses=[200, 201])
+
+
+def main():
+    parser = argparse.ArgumentParser(
+        description='Create draft comments in a Gerrit code review')
+    parser.add_argument('--comment',
+                        default='TODO: `unsafe` review',
+                        help='Text of the comment')
+    parser.add_argument(
+        '--trigger-regex',
+        default='\\bunsafe\\b',
+        help='Text/substring of lines that need new draft comments')
+    parser.add_argument(
+        '--path-regex',
+        default='third_party/rust/chromium_crates_io/vendor/.*\\.rs$',
+        help='Text/substring of lines that need new draft comments')
+    args = parser.parse_args()
+
+    trigger_regex = re.compile(args.trigger_regex)
+    path_regex = re.compile(args.path_regex)
+
+    curr_branch = Git('rev-parse', '--abbrev-ref', 'HEAD').strip()
+    upstream_branch = Git('rev-parse', '--abbrev-ref', '--symbolic-full-name',
+                          '@{u}').strip()
+    file_list = Git('diff', '--name-only', '--diff-filter=ACMR',
+                    f'{upstream_branch}..{curr_branch}')
+
+    draft_creator = DraftCreator()
+    for file_path in file_list.splitlines():
+        file_path = file_path.strip()
+        if not path_regex.search(file_path): continue
+        with open(file_path) as file:
+            lines = [line.rstrip() for line in file]
+        for line_number in range(len(lines)):
+            line = lines[line_number]
+            line_number = line_number + 1  # Line numbers in Gerrit start at 1
+            if not trigger_regex.search(line): continue
+            draft_creator.CreateDraft(file_path, line_number, args.comment)
+
+    return 0
+
+
+if __name__ == '__main__':
+    sys.exit(main())