[Youtube] Extract alerts from continuation (#144)

Related: #143

Authored by: colethedj

yt_dlp/extractor/youtube.py

@@ -2796,7 +2796,11 @@ class YoutubeTabIE(YoutubeBaseInfoExtractor):
                     # See: https://github.com/ytdl-org/youtube-dl/issues/28194
                     if response.get('continuationContents') or response.get('onResponseReceivedActions'):
                         break
-                    last_error = 'Incomplete data recieved'
+
+                    # Youtube may send alerts if there was an issue with the continuation page
+                    self._extract_alerts(response, expected=False)
+
+                    last_error = 'Incomplete data received'
                     if count >= retries:
                         self._downloader.report_error(last_error)
 
@@ -2982,13 +2986,13 @@ class YoutubeTabIE(YoutubeBaseInfoExtractor):
             self._extract_mix_playlist(playlist, playlist_id),
             playlist_id=playlist_id, playlist_title=title)
 
-    @staticmethod
-    def _extract_alerts(data):
+    def _extract_alerts(self, data, expected=False):
+
+        def _real_extract_alerts():
             for alert_dict in try_get(data, lambda x: x['alerts'], list) or []:
                 if not isinstance(alert_dict, dict):
                     continue
-            for renderer in alert_dict:
-                alert = alert_dict[renderer]
+                for alert in alert_dict.values():
                     alert_type = alert.get('type')
                     if not alert_type:
                         continue
@@ -3000,6 +3004,18 @@ class YoutubeTabIE(YoutubeBaseInfoExtractor):
                         if message:
                             yield alert_type, message
 
+        err_msg = None
+        for alert_type, alert_message in _real_extract_alerts():
+            if alert_type.lower() == 'error':
+                if err_msg:
+                    self._downloader.report_warning('YouTube said: %s - %s' % ('ERROR', err_msg))
+                err_msg = alert_message
+            else:
+                self._downloader.report_warning('YouTube said: %s - %s' % (alert_type, alert_message))
+
+        if err_msg:
+            raise ExtractorError('YouTube said: %s' % err_msg, expected=expected)
+
     def _extract_identity_token(self, webpage, item_id):
         ytcfg = self._extract_ytcfg(item_id, webpage)
         if ytcfg:
@@ -3024,16 +3040,7 @@ class YoutubeTabIE(YoutubeBaseInfoExtractor):
                 url, item_id,
                 'Downloading webpage%s' % (' (retry #%d)' % count if count else ''))
             data = self._extract_yt_initial_data(item_id, webpage)
-            err_msg = None
-            for alert_type, alert_message in self._extract_alerts(data):
-                if alert_type.lower() == 'error':
-                    if err_msg:
-                        self._downloader.report_warning('YouTube said: %s - %s' % ('ERROR', err_msg))
-                    err_msg = alert_message
-                else:
-                    self._downloader.report_warning('YouTube said: %s - %s' % (alert_type, alert_message))
-            if err_msg:
-                raise ExtractorError('YouTube said: %s' % err_msg, expected=True)
+            self._extract_alerts(data, expected=True)
             if data.get('contents') or data.get('currentVideoEndpoint'):
                 break
             if count >= retries: