[youtube] Retry on incomplete `ytInitialData`

Related: #116

yt_dlp/extractor/youtube.py

@@ -2998,6 +2998,10 @@ class YoutubeTabIE(YoutubeBaseInfoExtractor):
                 return self.url_result(video_id, ie=YoutubeIE.ie_key(), video_id=video_id)
             self.to_screen('Downloading playlist %s - add --no-playlist to just download video %s' % (playlist_id, video_id))
 
+        count = 0
+        retries = 3
+        while count < retries:
+            # Sometimes youtube returns a webpage with incomplete ytInitialData
             webpage = self._download_webpage(url, item_id)
             identity_token = self._extract_identity_token(webpage, item_id)
             data = self._extract_yt_initial_data(item_id, webpage)
@@ -3011,6 +3015,12 @@ class YoutubeTabIE(YoutubeBaseInfoExtractor):
                     self._downloader.report_warning('YouTube said: %s - %s' % (alert_type, alert_message))
             if err_msg:
                 raise ExtractorError('YouTube said: %s' % err_msg, expected=True)
+            if data.get('contents') or data.get('currentVideoEndpoint'):
+                break
+            count += 1
+            self.to_screen(
+                'Incomplete yt initial data recieved. Retrying (attempt %d of %d)...' % (count, retries))
+
         tabs = try_get(
             data, lambda x: x['contents']['twoColumnBrowseResultsRenderer']['tabs'], list)
         if tabs: