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

Code before:
                'video_id', default=display_id)

            dash_playlist_url = playlist_urls[0] or f'https://v.redd.it/{video_id}/DASHPlaylist.mpd'
            hls_playlist_url = re.sub(r'(f=[^&]+)', r'\1%2CsubsAll', playlist_urls[1]) or f'https://v.redd.it/{video_id}/HLSPlaylist.m3u8?f=hd%2CsubsAll'
            caption_url = f'https://v.redd.it/{video_id}/wh_ben_en.vtt'

            formats = [{
                'url': unescapeHTML(reddit_video['fallback_url']),
                'height': int_or_none(reddit_video.get('height')),
                'width': int_or_none(reddit_video.get('width')),
                'tbr': int_or_none(reddit_video.get('bitrate_kbps')),
                'acodec': 'none',
                'vcodec': 'h264',
                'ext': 'mp4',
                'format_id': 'fallback',
                'format_note': 'DASH video, mp4_dash',
            }]
            hls_fmts, subtitles = self._extract_m3u8_formats_and_subtitles(
                hls_playlist_url, display_id, 'mp4', m3u8_id='hls', fatal=False)
            formats.extend(hls_fmts)
            dash_fmts, dash_subs = self._extract_mpd_formats_and_subtitles(
                dash_playlist_url, display_id, mpd_id='dash', fatal=False)
            formats.extend(dash_fmts)
            self._merge_subtitles(dash_subs, target=subtitles)
            if not subtitles and self._is_valid_url(caption_url, video_id, item='subtitle'):
                self._merge_subtitles({'en': [{'url': caption_url}]}, target=subtitles)

            return {
                **info,
                'id': video_id,
                'display_id': display_id,
                'formats': formats,
                'subtitles': subtitles,
                'duration': int_or_none(reddit_video.get('duration')),
            }

        if parsed_url.netloc == 'v.redd.it':
            self.raise_no_formats('This video is processing', expected=True, video_id=video_id)
            return {
                **info,
                'id': parsed_url.path.split('/')[1],
                'display_id': video_id,
            }

        # Not hosted on reddit, must continue extraction
        return {
            **info,
            'display_id': video_id,
            '_type': 'url_transparent',
            'url': video_url,
        }

Review comment (suggestion):
if `subtitles` is falsy then there's nothing to merge:
```suggestion
                subtitles = {'en': [{'url': caption_url}]}
```

Code after:
        if reddit_video:
            playlist_urls = [
                try_get(reddit_video, lambda x: unescapeHTML(x[y]))
                for y in ('dash_url', 'hls_url')
            ]

            # Update video_id
            display_id = video_id
            video_id = self._search_regex(
                r'https?://v\.redd\.it/(?P<id>[^/?#&]+)', reddit_video['fallback_url'],
                'video_id', default=display_id)

            dash_playlist_url = playlist_urls[0] or f'https://v.redd.it/{video_id}/DASHPlaylist.mpd'
            hls_playlist_url = playlist_urls[1] or f'https://v.redd.it/{video_id}/HLSPlaylist.m3u8'
            qs = traverse_obj(parse_qs(hls_playlist_url), {
                'f': ('f', 0, {lambda x: ','.join([x, 'subsAll']) if x else 'hd,subsAll'}),
            })
            hls_playlist_url = update_url_query(hls_playlist_url, qs)

            formats = [{
                'url': unescapeHTML(reddit_video['fallback_url']),
                'height': int_or_none(reddit_video.get('height')),
                'width': int_or_none(reddit_video.get('width')),
                'tbr': int_or_none(reddit_video.get('bitrate_kbps')),
                'acodec': 'none',
                'vcodec': 'h264',
                'ext': 'mp4',
                'format_id': 'fallback',
                'format_note': 'DASH video, mp4_dash',
            }]
            hls_fmts, subtitles = self._extract_m3u8_formats_and_subtitles(
                hls_playlist_url, display_id, 'mp4', m3u8_id='hls', fatal=False)
            formats.extend(hls_fmts)
            dash_fmts, dash_subs = self._extract_mpd_formats_and_subtitles(
                dash_playlist_url, display_id, mpd_id='dash', fatal=False)
            formats.extend(dash_fmts)
            self._merge_subtitles(dash_subs, target=subtitles)

            return {
                **info,
                'id': video_id,
                'display_id': display_id,
                'formats': formats,
                'subtitles': subtitles or self.extract_subtitles(video_id),
                'duration': int_or_none(reddit_video.get('duration')),
            }

        if parsed_url.netloc == 'v.redd.it':
            self.raise_no_formats('This video is processing', expected=True, video_id=video_id)
            return {
                **info,