Repository: yt-dlp/yt-dlp
File: yt_dlp/extractor/bilibili.py (Python)

Code before:
                'text': traverse_obj(replies, ('content', 'message')),
                'id': replies.get('rpid'),
                'like_count': int_or_none(replies.get('like_count')),
                'parent': replies.get('parent'),
                'timestamp': unified_timestamp(replies.get('ctime_text'))
            }

            if (not traverse_obj(comment_api_raw_data, ('data', 'cursor', 'is_end'))):
                yield self._get_comments_reply(
                    root_id, traverse_obj(comment_api_raw_data, ('data', 'cursor', 'next')), display_id)

    def _get_comments(self, video_id, video_type):
        for i in itertools.count(0):
            comment_api_raw_data = self._download_json(
                'https://api.bilibili.tv/reply/web/root', video_id,
                note=f'Downloading comment page {i}',
                query={
                    'platform': 'web',
                    'pn': i,  # page number
                    'ps': 20,  # comment per page (default: 20)
                    'oid': video_id,
                    'type': 3 if video_type == "episode" else 1,  # 1: user generated content, 3: series content
                    'sort_type': 1,  # 1: best, 2: recent
                })

            for replies in traverse_obj(comment_api_raw_data, ('data', 'replies', ...)) or ():
                yield {
                    'author': traverse_obj(replies, ('member', 'name')),
                    'author_id': traverse_obj(replies, ('member', 'mid')),
                    'author_thumbnail': traverse_obj(replies, ('member', 'face')),
                    'text': traverse_obj(replies, ('content', 'message')),
                    'id': replies.get('rpid'),
                    'like_count': int_or_none(replies.get('like_count')),
                    'timestamp': unified_timestamp(replies.get('ctime_text')),
                    'author_is_uploader': traverse_obj(replies, ('member', 'type')),
                }
                if replies.get('count') > 0:
                    yield from self._get_comments_reply(replies.get('rpid'), display_id=video_id)

            if traverse_obj(comment_api_raw_data, ('data', 'cursor', 'is_end')):
                break

    def _real_extract(self, url):
        season_id, ep_id, aid = self._match_valid_url(url).group('season_id', 'ep_id', 'aid')
        video_id = ep_id or aid

        return {
            'id': video_id,
            **self._extract_video_metadata(url, video_id, season_id),
            'formats': self._get_formats(ep_id=ep_id, aid=aid),
            'subtitles': self.extract_subtitles(ep_id=ep_id, aid=aid),

Review comment (suggestion):
```suggestion
            for replies in traverse_obj(comment_api_raw_data, ('data', 'replies', ...)):
```
traverse_obj with ... always returns a list

Code after:
        if series_id:
            return f'https://www.bilibili.tv/en/play/{series_id}/{video_id}'
        return f'https://www.bilibili.tv/en/video/{video_id}'

    def _extract_video_metadata(self, url, video_id, season_id):
        url, smuggled_data = unsmuggle_url(url, {})
        if smuggled_data.get('title'):
            return smuggled_data

        webpage = self._download_webpage(url, video_id)
        # Bstation layout
        initial_data = (
            self._search_json(r'window\.__INITIAL_(?:DATA|STATE)__\s*=', webpage, 'preload state', video_id, default={})
            or self._search_nuxt_data(webpage, video_id, '__initialState', fatal=False, traverse=None))
        video_data = traverse_obj(
            initial_data, ('OgvVideo', 'epDetail'), ('UgcVideo', 'videoData'), ('ugc', 'archive'), expected_type=dict) or {}

        if season_id and not video_data:
            # Non-Bstation layout, read through episode list
            season_json = self._call_api(f'/web/v2/ogv/play/episodes?season_id={season_id}&platform=web', video_id)
            video_data = traverse_obj(season_json, (
                'sections', ..., 'episodes', lambda _, v: str(v['episode_id']) == video_id
            ), expected_type=dict, get_all=False)

        # XXX: webpage metadata may not accurate, it just used to not crash when video_data not found
        return merge_dicts(
            self._parse_video_metadata(video_data), self._search_json_ld(webpage, video_id, fatal=False), {
                'title': self._html_search_meta('og:title', webpage),
                'description': self._html_search_meta('og:description', webpage)
            })

    def _get_comments_reply(self, root_id, next_id=0, display_id=None):
        comment_api_raw_data = self._download_json(
            'https://api.bilibili.tv/reply/web/detail', display_id,
            note=f'Downloading reply comment of {root_id} - {next_id}',
            query={
                'platform': 'web',
                'ps': 20,  # comment's reply per page (default: 3)
                'root': root_id,
                'next': next_id,
            })

        for replies in traverse_obj(comment_api_raw_data, ('data', 'replies', ...)):
            yield {
                'author': traverse_obj(replies, ('member', 'name')),
                'author_id': traverse_obj(replies, ('member', 'mid')),
                'author_thumbnail': traverse_obj(replies, ('member', 'face')),
                'text': traverse_obj(replies, ('content', 'message')),
                'id': replies.get('rpid'),
                'like_count': int_or_none(replies.get('like_count')),
                'parent': replies.get('parent'),