OpenGraph playlist tags: better description

Use the playlist creator and number of items in the playlist instead of using the playlist description.
This should be more useful than the text description of the playlist.

listenbrainz/db/playlist.py

@@ -591,6 +591,24 @@ def get_recordings_for_playlists(db_conn, ts_conn, playlist_ids: List[int]):
             playlist_recordings_map[playlist_id] = []
     return dict(playlist_recordings_map)
 
+def get_recordings_count_for_playlist(ts_conn, playlist_id: int):
+    """ Get a count of recordings for a given playlist.
+
+    Arguments:
+        ts_conn: timsecale database connection
+        playlist_id: Numerical sequential id of a playlist (NOT its UUID)
+
+    Returns:
+        an integer of the number of recordings in the playlist """
+
+    query = text("""
+        SELECT COUNT(*)
+          FROM playlist.playlist_recording
+         WHERE playlist_id = :playlist_id
+    """)
+    result = ts_conn.execute(query, {"playlist_id": playlist_id})
+    return result.scalar()
+
 
 def _remove_old_collaborative_playlists(ts_conn, creator_id: int, created_for_id: int, source_patch: str):
     """

listenbrainz/webserver/views/playlist.py

@@ -23,9 +23,10 @@ def playlist_page(playlist_mbid: str):
     if is_valid_uuid(playlist_mbid):
         playlist = db_playlist.get_by_mbid(db_conn, ts_conn, playlist_mbid, False)
         if playlist is not None and playlist.is_visible_by(current_user_id):
+            recordings_count = db_playlist.get_recordings_count_for_playlist(ts_conn, playlist.id)
             og_meta_tags = {
                 "title": f'{playlist.name} — Playlist on ListenBrainz',
-                "description": playlist.description,
+                "description": f'Playlist by {playlist.creator} — {recordings_count} track{"s" if recordings_count > 1 else ""} — ListenBrainz',
                 "type": "music:playlist",
                 "url": f'{current_app.config["SERVER_ROOT_URL"]}/playlist/{playlist_mbid}',
                 "music:creator": f'{current_app.config["SERVER_ROOT_URL"]}/user/{playlist.creator}',