[youtube] Extract channel subscriber count (#2399)

Closes #2350
* Adds `channel_follower_count` field
Authored-by: coletdjnz

3 files changed, 50 insertions, 7 deletions

diff --git a/README.md b/README.md
index 71c4b24b3..358f563c1 100644
--- a/README.md
+++ b/README.md
@@ -1138,6 +1138,7 @@ The available fields are:
  - `uploader_id` (string): Nickname or id of the video uploader
  - `channel` (string): Full name of the channel the video is uploaded on
  - `channel_id` (string): Id of the channel
+ - `channel_follower_count` (numeric): Number of followers of the channel
  - `location` (string): Physical location where the video was filmed
  - `duration` (numeric): Length of the video in seconds
  - `duration_string` (string): Length of the video (HH:mm:ss)
diff --git a/yt_dlp/extractor/common.py b/yt_dlp/extractor/common.py
index 3f5e15103..e289a4ef8 100644
--- a/yt_dlp/extractor/common.py
+++ b/yt_dlp/extractor/common.py
@@ -261,6 +261,7 @@ class InfoExtractor(object):
                     fields. This depends on a particular extractor.
     channel_id:     Id of the channel.
     channel_url:    Full URL to a channel webpage.
+    channel_follower_count: Number of followers of the channel.
     location:       Physical location where the video was filmed.
     subtitles:      The available subtitles as a dictionary in the format
                     {tag: subformats}. "tag" is usually a language code, and
diff --git a/yt_dlp/extractor/youtube.py b/yt_dlp/extractor/youtube.py
index 988135516..09a0b2279 100644
--- a/yt_dlp/extractor/youtube.py
+++ b/yt_dlp/extractor/youtube.py
@@ -515,7 +515,7 @@ class YoutubeBaseInfoExtractor(InfoExtractor):
         Appears to be used to track session state
         """
         return get_first(
-            args, (('VISITOR_DATA', ('INNERTUBE_CONTEXT', 'client', 'visitorData'), ('responseContext', 'visitorData'))),
+            args, [('VISITOR_DATA', ('INNERTUBE_CONTEXT', 'client', 'visitorData'), ('responseContext', 'visitorData'))],
             expected_type=str)
 
     @property
@@ -1034,6 +1034,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                 'age_limit': 0,
                 'start_time': 1,
                 'end_time': 9,
+                'channel_follower_count': int
             }
         },
         {
@@ -1077,6 +1078,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                 'thumbnail': 'https://i.ytimg.com/vi/BaW_jenozKc/maxresdefault.jpg',
                 'live_status': 'not_live',
                 'age_limit': 0,
+                'channel_follower_count': int
             },
             'params': {
                 'skip_download': True,
@@ -1129,6 +1131,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                 'categories': ['Music'],
                 'age_limit': 0,
                 'alt_title': 'The Spark',
+                'channel_follower_count': int
             },
             'params': {
                 'youtube_include_dash_manifest': True,
@@ -1161,6 +1164,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                 'channel_id': 'UCzybXLxv08IApdjdN0mJhEg',
                 'playable_in_embed': True,
                 'view_count': int,
+                'channel_follower_count': int
             },
         },
         {
@@ -1188,6 +1192,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                 'like_count': int,
                 'duration': 177,
                 'playable_in_embed': True,
+                'channel_follower_count': int
             },
         },
         {
@@ -1215,6 +1220,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                 'categories': ['Entertainment'],
                 'duration': 106,
                 'channel_url': 'https://www.youtube.com/channel/UC1yoRdFoFJaCY-AGfD9W0wQ',
+                'channel_follower_count': int
             },
         },
         {
@@ -1246,6 +1252,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                 'channel_url': 'https://www.youtube.com/channel/UCdR3RSDPqub28LjZx0v9-aA',
                 'live_status': 'not_live',
                 'artist': 'OOMPH!',
+                'channel_follower_count': int
             },
         },
         {
@@ -1284,6 +1291,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                 'channel_url': 'https://www.youtube.com/channel/UCYEK6xds6eo-3tr4xRdflmQ',
                 'categories': ['Music'],
                 'album': 'Some Chords',
+                'channel_follower_count': int
             },
             'expected_warnings': [
                 'DASH manifest missing',
@@ -1316,6 +1324,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                 'live_status': 'was_live',
                 'view_count': int,
                 'channel_url': 'https://www.youtube.com/channel/UCTl3QQTvqHFjurroKxexy2Q',
+                'channel_follower_count': int
             },
             'params': {
                 'skip_download': 'requires avconv',
@@ -1347,6 +1356,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                 'like_count': int,
                 'live_status': 'not_live',
                 'availability': 'unlisted',
+                'channel_follower_count': int
             },
         },
         # url_encoded_fmt_stream_map is empty string
@@ -1515,6 +1525,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                 'playable_in_embed': True,
                 'like_count': int,
                 'age_limit': 0,
+                'channel_follower_count': int
             },
             'params': {
                 'skip_download': True,
@@ -1573,6 +1584,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                 'thumbnail': 'https://i.ytimg.com/vi_webp/M4gD1WSo5mA/maxresdefault.webp',
                 'live_status': 'not_live',
                 'playable_in_embed': True,
+                'channel_follower_count': int
             },
             'params': {
                 'skip_download': True,
@@ -1604,6 +1616,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                 'view_count': int,
                 'live_status': 'not_live',
                 'channel_url': 'https://www.youtube.com/channel/UCH1dpzjCEiGAt8CXkryhkZg',
+                'channel_follower_count': int
             },
             'params': {
                 'skip_download': True,
@@ -1667,6 +1680,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                 'like_count': int,
                 'playable_in_embed': True,
                 'live_status': 'not_live',
+                'channel_follower_count': int
             },
             'params': {
                 'skip_download': True,
@@ -1776,6 +1790,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                 'channel_id': 'UC-pWHpBjdGG69N9mM2auIAA',
                 'tags': 'count:11',
                 'live_status': 'not_live',
+                'channel_follower_count': int
             },
             'params': {
                 'skip_download': True,
@@ -1831,6 +1846,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                 'playable_in_embed': True,
                 'live_status': 'not_live',
                 'channel': 'ElevageOrVert',
+                'channel_follower_count': int
             },
             'params': {
                 'skip_download': True,
@@ -1864,6 +1880,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                 'view_count': int,
                 'duration': 522,
                 'channel': 'kudvenkat',
+                'channel_follower_count': int
             },
             'params': {
                 'skip_download': True,
@@ -1908,6 +1925,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                 'thumbnail': 'https://i.ytimg.com/vi/OtqTfy26tG0/maxresdefault.jpg',
                 'categories': ['Music'],
                 'playable_in_embed': True,
+                'channel_follower_count': int
             },
             'params': {
                 'skip_download': True,
@@ -1943,6 +1961,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                 'like_count': int,
                 'live_status': 'not_live',
                 'playable_in_embed': True,
+                'channel_follower_count': int
             }
         },
         {
@@ -1969,6 +1988,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                 'channel_url': 'https://www.youtube.com/channel/UC3o_t8PzBmXf5S9b7GLx1Mw',
                 'live_status': 'not_live',
                 'playable_in_embed': True,
+                'channel_follower_count': int
             },
             'params': {
                 'skip_download': True,
@@ -2010,6 +2030,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                 'like_count': int,
                 'live_status': 'not_live',
                 'playable_in_embed': True,
+                'channel_follower_count': int
             },
             'params': {
                 'format': '17',  # 3gp format available on android
@@ -2053,6 +2074,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                 'duration': 248,
                 'categories': ['Education'],
                 'age_limit': 0,
+                'channel_follower_count': int
             }, 'params': {'format': 'mhtml', 'skip_download': True}
         }
     ]
@@ -3489,7 +3511,11 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                         })
                 vsir = content.get('videoSecondaryInfoRenderer')
                 if vsir:
-                    info['channel'] = self._get_text(vsir, ('owner', 'videoOwnerRenderer', 'title'))
+                    vor = traverse_obj(vsir, ('owner', 'videoOwnerRenderer'))
+                    info.update({
+                        'channel': self._get_text(vor, 'title'),
+                        'channel_follower_count': self._get_count(vor, 'subscriberCountText')})
+
                     rows = try_get(
                         vsir,
                         lambda x: x['metadataRowContainer']['metadataRowContainerRenderer']['rows'],
@@ -3969,7 +3995,8 @@ class YoutubeTabBaseInfoExtractor(YoutubeBaseInfoExtractor):
             'view_count': self._get_count(playlist_stats, 1),
             'availability': self._extract_availability(data),
             'modified_date': strftime_or_none(last_updated_unix, '%Y%m%d'),
-            'playlist_count': self._get_count(playlist_stats, 0)
+            'playlist_count': self._get_count(playlist_stats, 0),
+            'channel_follower_count': self._get_count(data, ('header', ..., 'subscriberCountText')),
         }
         if not channel_id:
             metadata.update(self._extract_uploader(data))
@@ -4265,6 +4292,7 @@ class YoutubeTabIE(YoutubeTabBaseInfoExtractor):
             'tags': ['"критическое', 'мышление"', '"наука', 'просто"', 'математика', '"анализ', 'данных"'],
             'channel_url': 'https://www.youtube.com/channel/UCqj7Cz7revf5maW9g5pgNcg',
             'uploader_url': 'https://www.youtube.com/channel/UCqj7Cz7revf5maW9g5pgNcg',
+            'channel_follower_count': int
         },
     }, {
         'note': 'playlists, multipage, different order',
@@ -4281,6 +4309,7 @@ class YoutubeTabIE(YoutubeTabBaseInfoExtractor):
             'channel_id': 'UCqj7Cz7revf5maW9g5pgNcg',
             'channel': 'Igor Kleiner',
             'channel_url': 'https://www.youtube.com/channel/UCqj7Cz7revf5maW9g5pgNcg',
+            'channel_follower_count': int
         },
     }, {
         'note': 'playlists, series',
@@ -4297,6 +4326,7 @@ class YoutubeTabIE(YoutubeTabBaseInfoExtractor):
             'channel': '3Blue1Brown',
             'channel_id': 'UCYO_jab_esuFRV4b17AJtAw',
             'tags': ['Mathematics'],
+            'channel_follower_count': int
         },
     }, {
         'note': 'playlists, singlepage',
@@ -4313,6 +4343,7 @@ class YoutubeTabIE(YoutubeTabBaseInfoExtractor):
             'channel_id': 'UCAEtajcuhQ6an9WEzY9LEMQ',
             'tags': 'count:13',
             'channel': 'ThirstForScience',
+            'channel_follower_count': int
         }
     }, {
         'url': 'https://www.youtube.com/c/ChristophLaimer/playlists',
@@ -4366,6 +4397,7 @@ class YoutubeTabIE(YoutubeTabBaseInfoExtractor):
             'uploader_url': 'https://www.youtube.com/channel/UCKfVa3S1e4PHvxWcwyMMg8w',
             'channel_url': 'https://www.youtube.com/channel/UCKfVa3S1e4PHvxWcwyMMg8w',
             'channel_id': 'UCKfVa3S1e4PHvxWcwyMMg8w',
+            'channel_follower_count': int
         },
         'playlist_mincount': 2,
     }, {
@@ -4382,6 +4414,7 @@ class YoutubeTabIE(YoutubeTabBaseInfoExtractor):
             'channel_id': 'UCKfVa3S1e4PHvxWcwyMMg8w',
             'uploader_url': 'https://www.youtube.com/channel/UCKfVa3S1e4PHvxWcwyMMg8w',
             'channel': 'lex will',
+            'channel_follower_count': int
         },
         'playlist_mincount': 975,
     }, {
@@ -4398,6 +4431,7 @@ class YoutubeTabIE(YoutubeTabBaseInfoExtractor):
             'channel': 'lex will',
             'tags': ['bible', 'history', 'prophesy'],
             'channel_url': 'https://www.youtube.com/channel/UCKfVa3S1e4PHvxWcwyMMg8w',
+            'channel_follower_count': int
         },
         'playlist_mincount': 199,
     }, {
@@ -4414,6 +4448,7 @@ class YoutubeTabIE(YoutubeTabBaseInfoExtractor):
             'channel_url': 'https://www.youtube.com/channel/UCKfVa3S1e4PHvxWcwyMMg8w',
             'channel_id': 'UCKfVa3S1e4PHvxWcwyMMg8w',
             'tags': ['bible', 'history', 'prophesy'],
+            'channel_follower_count': int
         },
         'playlist_mincount': 17,
     }, {
@@ -4430,6 +4465,7 @@ class YoutubeTabIE(YoutubeTabBaseInfoExtractor):
             'channel_url': 'https://www.youtube.com/channel/UCKfVa3S1e4PHvxWcwyMMg8w',
             'channel_id': 'UCKfVa3S1e4PHvxWcwyMMg8w',
             'tags': ['bible', 'history', 'prophesy'],
+            'channel_follower_count': int
         },
         'playlist_mincount': 18,
     }, {
@@ -4446,6 +4482,7 @@ class YoutubeTabIE(YoutubeTabBaseInfoExtractor):
             'channel_url': 'https://www.youtube.com/channel/UCKfVa3S1e4PHvxWcwyMMg8w',
             'channel_id': 'UCKfVa3S1e4PHvxWcwyMMg8w',
             'tags': ['bible', 'history', 'prophesy'],
+            'channel_follower_count': int
         },
         'playlist_mincount': 12,
     }, {
@@ -4463,6 +4500,7 @@ class YoutubeTabIE(YoutubeTabBaseInfoExtractor):
             'tags': ['Mathematics'],
             'channel': '3Blue1Brown',
             'channel_id': 'UCYO_jab_esuFRV4b17AJtAw',
+            'channel_follower_count': int
         },
     }, {
         'url': 'https://invidio.us/channel/UCmlqkdCBesrv2Lak1mF_MxA',
@@ -4622,7 +4660,7 @@ class YoutubeTabIE(YoutubeTabBaseInfoExtractor):
     }, {
         'url': 'https://www.youtube.com/channel/UCoMdktPbSTixAyNGwb-UYkQ/live',
         'info_dict': {
-            'id': 'zpsbVPFwsqk',  # This will keep changing
+            'id': 'GgL890LIznQ',  # This will keep changing
             'ext': 'mp4',
             'title': str,
             'uploader': 'Sky News',
@@ -4633,17 +4671,18 @@ class YoutubeTabIE(YoutubeTabBaseInfoExtractor):
             'categories': ['News & Politics'],
             'tags': list,
             'like_count': int,
-            'release_timestamp': 1640164857,
+            'release_timestamp': 1642502819,
             'channel': 'Sky News',
             'channel_id': 'UCoMdktPbSTixAyNGwb-UYkQ',
             'age_limit': 0,
             'view_count': int,
-            'thumbnail': 'https://i.ytimg.com/vi/zpsbVPFwsqk/maxresdefault_live.jpg',
+            'thumbnail': 'https://i.ytimg.com/vi/GgL890LIznQ/maxresdefault_live.jpg',
             'playable_in_embed': True,
-            'release_date': '20211222',
+            'release_date': '20220118',
             'availability': 'public',
             'live_status': 'is_live',
             'channel_url': 'https://www.youtube.com/channel/UCoMdktPbSTixAyNGwb-UYkQ',
+            'channel_follower_count': int
         },
         'params': {
             'skip_download': True,
@@ -4825,6 +4864,7 @@ class YoutubeTabIE(YoutubeTabBaseInfoExtractor):
         'info_dict': {
             'id': 'recommended',
             'title': 'recommended',
+            'tags': [],
         },
         'playlist_mincount': 50,
         'params': {
@@ -4845,6 +4885,7 @@ class YoutubeTabIE(YoutubeTabBaseInfoExtractor):
             'tags': [],
             'channel_url': 'https://www.youtube.com/channel/UCu6mSoMNzHQiBIOCkHUa2Aw',
             'uploader_url': 'https://www.youtube.com/channel/UCu6mSoMNzHQiBIOCkHUa2Aw',
+            'channel_follower_count': int
         },
         'playlist_mincount': 650,
         'params': {