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

Code before:
            check_form = {
                'fb_dtsg': fb_dtsg,
                'h': h,
                'name_action_selected': 'dont_save',
            }
            check_req = Request(self._CHECKPOINT_URL, urlencode_postdata(check_form))
            check_req.headers['Content-Type'] = 'application/x-www-form-urlencoded'
            check_response = self._download_webpage(check_req, None,
                                                    note='Confirming login')
            if re.search(r'id="checkpointSubmitButton"', check_response) is not None:
                self.report_warning('Unable to confirm login, you have to login in your browser and authorize the login.')
        except network_exceptions as err:
            self.report_warning('unable to log in: %s' % error_to_compat_str(err))
            return

    def _extract_from_url(self, url, video_id):
        webpage = self._download_webpage(
            url.replace('://m.facebook.com/', '://www.facebook.com/'), video_id)

        def extract_metadata(webpage):
            post_data = [self._parse_json(j, video_id, fatal=False) for j in re.findall(
                r'data-sjs>({.*?ScheduledServerJS.*?})</script>', webpage)]
            post = traverse_obj(post_data, (
                ..., 'require', ..., ..., ..., '__bbox', 'require', ..., ..., ..., '__bbox', 'result', 'data'), expected_type=dict) or []
            snippet = traverse_obj(post, (..., 'video', ..., 'attachments', ..., lambda k, v: (
                k == 'media' and str(v['id']) == video_id and v['__typename'] == 'Video')), expected_type=dict) or {}
            locale = self._html_search_meta(['og:locale', 'twitter:locale'], webpage, 'locale', default='en_US')
            captions = get_first(snippet, 'video_available_captions_locales', 'captions_url')
            useIsVideoBroadcast = get_first(snippet, ('is_video_broadcast')) or False
            automatic_captions = {}
            subtitles = {}
            if isinstance(captions, str):
                subtitles[locale] = [{'ext': determine_ext(captions, default_ext='srt'), 'url': captions}]
            elif isinstance(captions, list):
                if len(captions) > 1:
                    captions = sorted(captions, key=lambda c: (c['locale'] != locale, c['locale']))
                for c in captions:
                    s = {
                        'ext': determine_ext(c['captions_url'], default_ext='srt'),
                        'url': c['captions_url'],
                        'name': (c['localized_language']
                                 + (' (' + c['localized_country'] + ')' if c['localized_country'] else '')
                                 + (' (' + c['localized_creation_method'] + ')' if c['localized_creation_method'] else '')),
                    }
                    if c['localized_creation_method'] or useIsVideoBroadcast:
                        automatic_captions.setdefault(c['locale'], []).append(s)
                    else:
                        subtitles.setdefault(c['locale'], []).append(s)
            media = traverse_obj(post, (..., 'attachments', ..., lambda k, v: (
                k == 'media' and str(v['id']) == video_id and v['__typename'] == 'Video')), expected_type=dict)
            title = get_first(media, ('title', 'text'))

Review comment (suggestion):
Remove `expected_type=dict` because filtering by key/value already expects dicts
Remove `or {}` because `snippet` is going to be a list due to branching in traversal
```suggestion
            snippet = traverse_obj(post, (..., 'video', ..., 'attachments', ..., lambda k, v: (
                k == 'media' and str(v['id']) == video_id and v['__typename'] == 'Video')))
```

Code after:

            check_form = {
                'fb_dtsg': fb_dtsg,
                'h': h,
                'name_action_selected': 'dont_save',
            }
            check_req = Request(self._CHECKPOINT_URL, urlencode_postdata(check_form))
            check_req.headers['Content-Type'] = 'application/x-www-form-urlencoded'
            check_response = self._download_webpage(check_req, None,
                                                    note='Confirming login')
            if re.search(r'id="checkpointSubmitButton"', check_response) is not None:
                self.report_warning('Unable to confirm login, you have to login in your browser and authorize the login.')
        except network_exceptions as err:
            self.report_warning('unable to log in: %s' % error_to_compat_str(err))
            return

    def _extract_from_url(self, url, video_id):
        webpage = self._download_webpage(
            url.replace('://m.facebook.com/', '://www.facebook.com/'), video_id)

        def extract_metadata(webpage):
            post_data = [self._parse_json(j, video_id, fatal=False) for j in re.findall(
                r'data-sjs>({.*?ScheduledServerJS.*?})</script>', webpage)]
            post = traverse_obj(post_data, (
                ..., 'require', ..., ..., ..., '__bbox', 'require', ..., ..., ..., '__bbox', 'result', 'data'), expected_type=dict) or []

            automatic_captions, subtitles = {}, {}
            subs_data = traverse_obj(post, (..., 'video', ..., 'attachments', ..., lambda k, v: (
                k == 'media' and str(v['id']) == video_id and v['__typename'] == 'Video')))
            is_video_broadcast = get_first(subs_data, 'is_video_broadcast', expected_type=bool)
            captions = get_first(subs_data, 'video_available_captions_locales', 'captions_url')
            if url_or_none(captions):  # if subs_data only had a 'captions_url'
                locale = self._html_search_meta(['og:locale', 'twitter:locale'], webpage, 'locale', default='en_US')
                subtitles[locale] = [{'url': captions}]
            # or else subs_data had 'video_available_captions_locales', a list of dicts
            for caption in traverse_obj(captions, (
                {lambda x: sorted(x, key=lambda c: c['locale'])}, lambda _, v: v['captions_url'])
            ):
                lang = caption.get('localized_language') or ''
                subs = {
                    'url': caption['captions_url'],
                    'name': format_field(caption, 'localized_country', f'{lang} (%s)', default=lang),
                }
                if caption.get('localized_creation_method') or is_video_broadcast:
                    automatic_captions.setdefault(caption['locale'], []).append(subs)
                else:
                    subtitles.setdefault(caption['locale'], []).append(subs)

            media = traverse_obj(post, (..., 'attachments', ..., lambda k, v: (
                k == 'media' and str(v['id']) == video_id and v['__typename'] == 'Video')), expected_type=dict)
            title = get_first(media, ('title', 'text'))