[extractor/youtube] Add `innertube_host` and `innertube_key` extractor args (#3916)

Allows user to override Innertube API host or key for all requests
Authored by: coletdjnz

README.md

@@ -1716,6 +1716,10 @@ The following extractors use this feature:
 * `comment_sort`: `top` or `new` (default) - choose comment sorting mode (on YouTube's side)
 * `max_comments`: Limit the amount of comments to gather. Comma-separated list of integers representing `max-comments,max-parents,max-replies,max-replies-per-thread`. Default is `all,all,all,all`
     * E.g. `all,all,1000,10` will get a maximum of 1000 replies total, with up to 10 replies per thread. `1000,all,100` will get a maximum of 1000 comments, with a maximum of 100 replies total
+* `innertube_host`: Innertube API host to use for all API requests 
+  * e.g. `studio.youtube.com`, `youtubei.googleapis.com`
+  * Note: Cookies exported from `www.youtube.com` will not work with hosts other than `*.youtube.com`
+* `innertube_key`: Innertube API key to use for all API requests
 
 #### youtubetab (YouTube playlists, channels, feeds, etc.)
 * `skip`: One or more of `webpage` (skip initial webpage download), `authcheck` (allow the download of playlists requiring authentication when no initial webpage is downloaded. This may cause unwanted behavior, see [#1122](https://github.com/yt-dlp/yt-dlp/pull/1122) for more details)

yt_dlp/extractor/youtube.py

@@ -421,6 +421,10 @@ class YoutubeBaseInfoExtractor(InfoExtractor):
             ytcfg, (lambda x: x['INNERTUBE_CLIENT_VERSION'],
                     lambda x: x['INNERTUBE_CONTEXT']['client']['clientVersion']), compat_str, default_client)
 
+    def _select_api_hostname(self, req_api_hostname, default_client=None):
+        return (self._configuration_arg('innertube_host', [''], ie_key=YoutubeIE.ie_key())[0]
+                or req_api_hostname or self._get_innertube_host(default_client or 'web'))
+
     def _extract_api_key(self, ytcfg=None, default_client='web'):
         return self._ytcfg_get_safe(ytcfg, lambda x: x['INNERTUBE_API_KEY'], compat_str, default_client)
 
@@ -469,11 +473,13 @@ class YoutubeBaseInfoExtractor(InfoExtractor):
         real_headers.update({'content-type': 'application/json'})
         if headers:
             real_headers.update(headers)
+        api_key = (self._configuration_arg('innertube_key', [''], ie_key=YoutubeIE.ie_key(), casesense=True)[0]
+                   or api_key or self._extract_api_key(default_client=default_client))
         return self._download_json(
-            f'https://{api_hostname or self._get_innertube_host(default_client)}/youtubei/v1/{ep}',
+            f'https://{self._select_api_hostname(api_hostname, default_client)}/youtubei/v1/{ep}',
             video_id=video_id, fatal=fatal, note=note, errnote=errnote,
             data=json.dumps(data).encode('utf8'), headers=real_headers,
-            query={'key': api_key or self._extract_api_key(), 'prettyPrint': 'false'})
+            query={'key': api_key, 'prettyPrint': 'false'})
 
     def extract_yt_initial_data(self, item_id, webpage, fatal=True):
         return self._search_json(self._YT_INITIAL_DATA_RE, webpage, 'yt initial data', item_id, fatal=fatal)
@@ -545,7 +551,7 @@ class YoutubeBaseInfoExtractor(InfoExtractor):
             self, *, ytcfg=None, account_syncid=None, session_index=None,
             visitor_data=None, identity_token=None, api_hostname=None, default_client='web'):
 
-        origin = 'https://' + (api_hostname if api_hostname else self._get_innertube_host(default_client))
+        origin = 'https://' + (self._select_api_hostname(api_hostname, default_client))
         headers = {
             'X-YouTube-Client-Name': compat_str(
                 self._ytcfg_get_safe(ytcfg, lambda x: x['INNERTUBE_CONTEXT_CLIENT_NAME'], default_client=default_client)),