lastgenre: Fix fetching artist genre for multi-artist albums

beetsplug/lastgenre/__init__.py

@@ -28,7 +28,7 @@
 import traceback
 from functools import singledispatchmethod
 from pathlib import Path
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, cast
 
 import pylast
 import yaml
@@ -300,24 +300,18 @@ def _last_lookup(self, entity, method, *args):
         self._tunelog("last.fm (unfiltered) {} tags: {}", entity, genre)
         return genre
 
-    def fetch_album_genre(self, obj):
-        """Return raw album genres from Last.fm for this Item or Album."""
-        return self._last_lookup(
-            "album", LASTFM.get_album, obj.albumartist, obj.album
-        )
+    def fetch_album_genre(self, albumartist, album):
+        """Return album genres from Last.fm for the album by albumartist."""
+        return self._last_lookup("album", LASTFM.get_album, albumartist, album)
 
-    def fetch_album_artist_genre(self, obj):
-        """Return raw album artist genres from Last.fm for this Item or Album."""
-        return self._last_lookup("artist", LASTFM.get_artist, obj.albumartist)
+    def fetch_artist_genre(self, artistname):
+        """Return artist genres from Last.fm for the artistname."""
+        return self._last_lookup("artist", LASTFM.get_artist, artistname)
 
-    def fetch_artist_genre(self, item):
-        """Returns raw track artist genres from Last.fm for this Item."""
-        return self._last_lookup("artist", LASTFM.get_artist, item.artist)
-
-    def fetch_track_genre(self, obj):
-        """Returns raw track genres from Last.fm for this Item."""
+    def fetch_track_genre(self, trackartist, tracktitle):
+        """Returns genres from Last.fm for the tracktitle."""
         return self._last_lookup(
-            "track", LASTFM.get_track, obj.artist, obj.title
+            "track", LASTFM.get_track, trackartist, tracktitle
         )
 
     # Main processing: _get_genre() and helpers.
@@ -405,14 +399,14 @@ def _try_resolve_stage(stage_label: str, keep_genres, new_genres):
         # Run through stages: track, album, artist,
         # album artist, or most popular track genre.
         if isinstance(obj, library.Item) and "track" in self.sources:
-            if new_genres := self.fetch_track_genre(obj):
+            if new_genres := self.fetch_track_genre(obj.artist, obj.title):
                 if result := _try_resolve_stage(
                     "track", keep_genres, new_genres
                 ):
                     return result
 
         if "album" in self.sources:
-            if new_genres := self.fetch_album_genre(obj):
+            if new_genres := self.fetch_album_genre(obj.albumartist, obj.album):
                 if result := _try_resolve_stage(
                     "album", keep_genres, new_genres
                 ):
@@ -421,20 +415,35 @@ def _try_resolve_stage(stage_label: str, keep_genres, new_genres):
         if "artist" in self.sources:
             new_genres = []
             if isinstance(obj, library.Item):
-                new_genres = self.fetch_artist_genre(obj)
+                new_genres = self.fetch_artist_genre(obj.artist)
                 stage_label = "artist"
             elif obj.albumartist != config["va_name"].as_str():
-                new_genres = self.fetch_album_artist_genre(obj)
+                new_genres = self.fetch_artist_genre(obj.albumartist)
                 stage_label = "album artist"
+                if not new_genres:
+                    self._tunelog(
+                        'No album artist genre found for "{}", '
+                        "trying multi-valued field...",
+                        obj.albumartist,
+                    )
+                    for albumartist in obj.albumartists:
+                        self._tunelog(
+                            'Fetching artist genre for "{}"', albumartist
+                        )
+                        new_genres += self.fetch_artist_genre(albumartist)
+                    if new_genres:
+                        stage_label = "multi-valued album artist"
             else:
                 # For "Various Artists", pick the most popular track genre.
                 item_genres = []
-                for item in obj.items():
+                for item in cast("list[Item]", obj.items()):
                     item_genre = None
                     if "track" in self.sources:
-                        item_genre = self.fetch_track_genre(item)
+                        item_genre = self.fetch_track_genre(
+                            item.artist, item.title
+                        )
                     if not item_genre:
-                        item_genre = self.fetch_artist_genre(item)
+                        item_genre = self.fetch_artist_genre(item.artist)
                     if item_genre:
                         item_genres += item_genre
                 if item_genres:

docs/changelog.rst

@@ -43,6 +43,11 @@ Bug fixes:
   accepted a list of strings). :bug:`5962`
 - Fix a bug introduced in release 2.4.0 where import from any valid
   import-log-file always threw a "none of the paths are importable" error.
+- :doc:`plugins/lastgenre`: Fix the issue were last.fm does not give a result in
+  the artist genre stage because multi-artists "concatenation" words (like
+  "feat." "+", or "&" prevent exact matches. Using the albumartists list field
+  and fetching a genre for each artist separately massively improves the chance
+  to get a valid result in that stage.
 
 For plugin developers: