[youtube] Support channel search

Code from cd684175ad

youtube_dl/extractor/youtube.py

@@ -2438,6 +2438,17 @@ class YoutubeTabIE(YoutubeBaseInfoExtractor):
     }, {
         'url': 'https://www.youtube.com/watch?list=PLW4dVinRY435CBE_JD3t-0SRXKfnZHS1P&feature=youtu.be&v=M9cJMXmQ_ZU',
         'only_matching': True,
+    }, {
+        'note': 'Search tab',
+        'url': 'https://www.youtube.com/c/3blue1brown/search?query=linear%20algebra',
+        'playlist_mincount': 40,
+        'info_dict': {
+            'id': 'UCYO_jab_esuFRV4b17AJtAw',
+            'title': '3Blue1Brown - Search - linear algebra',
+            'description': 'md5:e1384e8a133307dd10edee76e875d62f',
+            'uploader': '3Blue1Brown',
+            'uploader_id': 'UCYO_jab_esuFRV4b17AJtAw',
+        }
     }]
 
     @classmethod
@@ -2835,8 +2846,9 @@ class YoutubeTabIE(YoutubeBaseInfoExtractor):
     @staticmethod
     def _extract_selected_tab(tabs):
         for tab in tabs:
-            if try_get(tab, lambda x: x['tabRenderer']['selected'], bool):
-                return tab['tabRenderer']
+            renderer = dict_get(tab, ('tabRenderer', 'expandableTabRenderer')) or {}
+            if renderer.get('selected') is True:
+                return renderer
         else:
             raise ExtractorError('Unable to find selected tab')
 
@@ -2893,6 +2905,8 @@ class YoutubeTabIE(YoutubeBaseInfoExtractor):
             title = channel_title or item_id
             if tab_title:
                 title += ' - %s' % tab_title
+            if selected_tab.get('expandedText'):
+                title += ' - %s' % selected_tab['expandedText']
             description = renderer.get('description')
             playlist_id = renderer.get('externalId')
         else: