lastgenre: Dedup fallback handling in _get_genre

and fix fallback types

Author: JOJ0

beetsplug/lastgenre/__init__.py

@@ -417,6 +417,12 @@ def _get_genre(self, obj: LibModel) -> tuple[list[str], str]:
         and the whitelist feature was disabled.
         """
 
+        def _fallback_stage() -> tuple[list[str], str]:
+            """Return the fallback genre and label."""
+            if fallback := self.config["fallback"].get():
+                return [fallback], "fallback"
+            return [], "fallback unconfigured"
+
         def _try_resolve_stage(
             stage_label: str,
             keep_genres: list[str],
@@ -453,8 +459,7 @@ def _try_resolve_stage(
                 ):
                     return result
 
-                # Return fallback string (None if not set).
-                return self.config["fallback"].get(), "fallback"
+                return _fallback_stage()
 
             # If cleanup_existing is not set, the pre-populated tags are
             # returned as-is.
@@ -548,7 +553,14 @@ def _try_resolve_stage(
 
         # Nothing found, leave original if configured and valid.
         if genres and self.config["keep_existing"].get():
-            artist = self._artist_for_filter(obj)
+            if isinstance(obj, library.Item):
+                # For track items, use track artist (important for compilations).
+                artist = getattr(obj, "artist", None)
+            else:
+                # For albums, prefer albumartist, fall back to artist.
+                artist = getattr(obj, "albumartist", None) or getattr(
+                    obj, "artist", None
+                )
             if valid_genres := self._filter_valid(genres, artist=artist):
                 return valid_genres, "original fallback"
             # If the original genre doesn't match a whitelisted genre, check
@@ -558,12 +570,7 @@ def _try_resolve_stage(
             ):
                 return result
 
-        # Return fallback as a list.
-        if fallback := self.config["fallback"].get():
-            return [fallback], "fallback"
-
-        # No fallback configured.
-        return [], "fallback unconfigured"
+        return _fallback_stage()
 
     # Beets plugin hooks and CLI.