Fix linting

README.md

@@ -1762,11 +1762,11 @@ Metadata fields            | From
 `description`,  `synopsis` | `description`
 `purl`, `comment`          | `webpage_url`
 `track`                    | `track_number`
-`artist`                   | `artists`, `creator`, `uploader` or `uploader_id`
+`artist`                   | `artist`, `creator`, `uploader` or `uploader_id`
-`composer`                 | `composers`
+`composer`                 | `composer`
-`genre`                    | `genres`
+`genre`                    | `genre`
 `album`                    | `album`
-`album_artist`             | `album_artists`
+`album_artist`             | `album_artist`
 `disc`                     | `disc_number`
 `show`                     | `series`
 `season_number`            | `season_number`

yt_dlp/YoutubeDL.py

@@ -24,6 +24,7 @@ import traceback
 import unicodedata
 
 from .cache import Cache
+
 from .compat import functools, urllib  # isort: split
 from .compat import compat_os_name, compat_shlex_quote, urllib_req_to_req
 from .cookies import LenientSimpleCookie, load_cookies
@@ -2648,8 +2649,10 @@ class YoutubeDL:
             'genre': 'genres',
         }
         for deprecated_field, new_field in deprecated_multivalue_fields.items():
-            if info_dict.get(deprecated_field):
+            if deprecated_value := info_dict.get(deprecated_field):
-                info_dict[new_field] = re.split(r', ?', info_dict[deprecated_field])
+                info_dict[new_field] = re.split(r', ?', deprecated_value)
+            elif new_value := info_dict.get(new_field):
+                info_dict[deprecated_field] = new_value.join(', ')
 
     def _raise_pending_errors(self, info):
         err = info.pop('__pending_error', None)

yt_dlp/postprocessor/ffmpeg.py

@@ -755,11 +755,11 @@ class FFmpegMetadataPP(FFmpegPostProcessor):
         add(('description', 'synopsis'), 'description')
         add(('purl', 'comment'), 'webpage_url')
         add('track', 'track_number')
-        add('artist', ('artists', 'creator', 'uploader', 'uploader_id'))
+        add('artist', ('artist', 'creator', 'uploader', 'uploader_id'))
-        add('composer', 'composers')
+        add('composer', 'composer')
-        add('genre', 'genres')
+        add('genre', 'genre')
         add('album')
-        add('album_artist', 'album_artists')
+        add('album_artist', 'album_artist')
         add('disc', 'disc_number')
         add('show', 'series')
         add('season_number')