Include playlist description and view count when using youtube-dl with `--flat-playlist -J` on a YouTube playlist

Checklist

• I’m reporting a feature request
• I’ve verified that I’m running youtube-dl version 2021.06.06
• I’ve searched the bugtracker for similar feature requests including closed ones

Description

I have been trying to find a way to quickly get information and video URLs/titles from a YouTube playlist, so far I have found that using youtube-dl <playlist URL> -J --flatplaylist is the closest to what I want, returning a list of all videos as well as the uploader of the playlist and the playlist name.
However, it would be extremely useful if it could also return even more information about the playlist, like the playlist’s Description & view count.

[nose-gnome]

I have made pull request #30161 with the changes you have shown, and the changes I made

[nose-gnome]

Thank you for your response showing the solution for the missing playlist description.

On the matter of obtaining extra metadata like view_count, I found that they are stored inside:

 {
     'sidebar': {
         'metadata': {...} // Where the Title & Description are currently being extracted from.
 
         'playlistSidebarRenderer': {
             'items': [
                 0: {                
                     // As well as containing stats, items[0] also contains re-occurring information like Title, Description & thumbnail
 
                     'stats': [
                         0: {...}, // 0 Contains the number for videos in the playlist
                         1: {...}, // 1 Contains how many views the playlist has
                         2: {...} //  2 Contains the date of the last time the playlist was updated.
                     ]
                 }
             ]
         }
     }
 }

So, by making the following changes, I found how to include the view_count and the last_updated date in the output:

--- a/youtube_dl/extractor/common.py
+++ b/youtube_dl/extractor/common.py
@@ -968,7 +968,8 @@ class InfoExtractor(object):
             urls, playlist_id=playlist_id, playlist_title=playlist_title)
 
     @staticmethod
-    def playlist_result(entries, playlist_id=None, playlist_title=None, playlist_description=None):
+    def playlist_result(entries, playlist_id=None, playlist_title=None, playlist_description=None,
+                        playlist_view_count=None, playlist_last_update=None):
         """Returns a playlist"""
         video_info = {'_type': 'playlist',
                       'entries': entries}
@@ -978,6 +979,10 @@ class InfoExtractor(object):
             video_info['title'] = playlist_title
         if playlist_description:
             video_info['description'] = playlist_description
+        if playlist_view_count:
+            video_info['view_count'] = playlist_view_count
+        if playlist_last_update:
+            video_info['last_updated'] = playlist_last_update
         return video_info
 
     def _search_regex(self, pattern, string, name, default=NO_DEFAULT, fatal=True, flags=0, group=None):

--- a/youtube_dl/extractor/youtube.py
+++ b/youtube_dl/extractor/youtube.py
@@ -2785,6 +2785,18 @@ class YoutubeTabIE(YoutubeBaseInfoExtractor):
                 data, lambda x: x['metadata']['playlistMetadataRenderer'], dict)
             if renderer:
                 title = renderer.get('title')
+                description = renderer.get('description')
+
+                stats = try_get(
+                    data, lambda x: x['sidebar']['playlistSidebarRenderer']['items'][0]['playlistSidebarPrimaryInfoRenderer']['stats'])
+                view_count_text = try_get(
+                    stats, lambda x: x[1]['simpleText'], compat_str) or ''
+                view_count = str_to_int(self._search_regex(
+                    r'^([\d,]+)', re.sub(r'\s', '', view_count_text),
+                    'view count', default=None))
+
+                last_updated_text = try_get(stats, lambda x: x[2]['runs'][1]['text'])
+                last_updated = unified_strdate(last_updated_text)
             else:
                 renderer = try_get(
                     data, lambda x: x['header']['hashtagHeaderRenderer'], dict)
@@ -2793,7 +2805,9 @@ class YoutubeTabIE(YoutubeBaseInfoExtractor):
         playlist = self.playlist_result(
             self._entries(selected_tab, item_id, webpage),
             playlist_id=playlist_id, playlist_title=title,
-            playlist_description=description)
+            playlist_description=description,
+            playlist_view_count=view_count,
+            playlist_last_update=last_updated)
         playlist.update(self._extract_uploader(data))
         return playlist

Then:

youtube-dl --flat-playlist -J PLZHQObOWTQDMXMi3bUMThGdYqos36X_lA

->

{
  "_type": "playlist",
  "entries": [
    {
      "_type": "url",
      "ie_key": "Youtube",
      "id": "GNcFjFmqEc8",
      "url": "GNcFjFmqEc8",
      "title": "But why is a sphere's surface area four times its shadow?",
      "description": null,
      "duration": 1021,
      "view_count": null,
      "uploader": "3Blue1Brown"
    },
    {
      "_type": "url",
      "ie_key": "Youtube",
      "id": "OkmNXy7er84",
      "url": "OkmNXy7er84",
      "title": "The hardest problem on the hardest test",
      "description": null,
      "duration": 675,
      "view_count": null,
      "uploader": "3Blue1Brown"
    },
    {
      "_type": "url",
      "ie_key": "Youtube",
      "id": "AmgkSdhK4K8",
      "url": "AmgkSdhK4K8",
      "title": "Who cares about topology?   (Inscribed rectangle problem)",
      "description": null,
      "duration": 1096,
      "view_count": null,
      "uploader": "3Blue1Brown"
    },
    {
      "_type": "url",
      "ie_key": "Youtube",
      "id": "pQa_tWZmlGs",
      "url": "pQa_tWZmlGs",
      "title": "Why slicing a cone gives an ellipse",
      "description": null,
      "duration": 772,
      "view_count": null,
      "uploader": "3Blue1Brown"
    },
    {
      "_type": "url",
      "ie_key": "Youtube",
      "id": "yuVqxCSsE7c",
      "url": "yuVqxCSsE7c",
      "title": "Sneaky Topology | The Borsuk-Ulam theorem and stolen necklaces",
      "description": null,
      "duration": 1190,
      "view_count": null,
      "uploader": "3Blue1Brown"
    },
    {
      "_type": "url",
      "ie_key": "Youtube",
      "id": "zwAD6dRSVyI",
      "url": "zwAD6dRSVyI",
      "title": "Thinking outside the 10-dimensional box",
      "description": null,
      "duration": 1627,
      "view_count": null,
      "uploader": "3Blue1Brown"
    },
    {
      "_type": "url",
      "ie_key": "Youtube",
      "id": "K8P8uFahAgc",
      "url": "K8P8uFahAgc",
      "title": "Circle Division Solution",
      "description": null,
      "duration": 533,
      "view_count": null,
      "uploader": "3Blue1Brown"
    }
  ],
  "id": "PLZHQObOWTQDMXMi3bUMThGdYqos36X_lA",
  "title": "Geometry",
  "view_count": 125486,
  "last_updated": "20191121",
  "uploader": "3Blue1Brown",
  "uploader_id": "UCYO_jab_esuFRV4b17AJtAw",
  "uploader_url": "https://www.youtube.com/c/3blue1brown",
  "extractor": "youtube:tab",
  "webpage_url": "https://www.youtube.com/playlist?list=PLZHQObOWTQDMXMi3bUMThGdYqos36X_lA",
  "webpage_url_basename": "playlist",
  "extractor_key": "YoutubeTab"
}