lastgenre: Apply canonicalization to genres of items with no Last.fm results

beetsplug/lastgenre/__init__.py

@@ -480,15 +480,11 @@ def _try_resolve_stage(
 
         # Nothing found, leave original if configured and valid.
         if obj.genre and self.config["keep_existing"]:
-            if not self.whitelist or self._is_valid(obj.genre.lower()):
-                return obj.genre, "original fallback"
-            else:
-                # If the original genre doesn't match a whitelisted genre, check
-                # if we can canonicalize it to find a matching, whitelisted genre!
-                if result := _try_resolve_stage(
-                    "original fallback", keep_genres, []
-                ):
-                    return result
+            # Process existing genres to apply whitelist and canonicalization
+            if result := _try_resolve_stage(
+                "original fallback", keep_genres, []
+            ):
+                return result
 
         # Return fallback string.
         if fallback := self.config["fallback"].get():

beetsplug/lastgenre/genres-tree.yaml

@@ -791,3 +791,5 @@
     - world fusion
     - worldbeat
 
+- '':
+  - blacklisted genre

docs/changelog.rst

@@ -24,6 +24,8 @@ Bug fixes
 - :doc:`plugins/musicbrainz`: Fix fetching very large releases that have more
   than 500 tracks. :bug:`6355`
 - :doc:`plugins/badfiles`: Fix number of found errors in log message
+- :doc:`plugins/lastgenre`: Apply canonicalization to genres of items with no
+  Last.fm results
 
 ..
     For plugin developers

test/plugins/test_lastgenre.py

@@ -338,7 +338,7 @@ def test_sort_by_depth(self):
                 "album": None,
                 "artist": None,
             },
-            ("any existing", "original fallback"),
+            ("Any Existing", "keep + original fallback, any"),
         ),
         # 7.1 - Keep the original genre when force and keep_existing are on, and
         # whitelist is enabled, and genre is valid.
@@ -358,7 +358,7 @@ def test_sort_by_depth(self):
                 "album": None,
                 "artist": None,
             },
-            ("Jazz", "original fallback"),
+            ("Jazz", "keep + original fallback, whitelist"),
         ),
         # 7.2 - Return the configured fallback when force is on but
         # keep_existing is not.
@@ -380,6 +380,26 @@ def test_sort_by_depth(self):
             },
             ("fallback genre", "fallback"),
         ),
+        # 7.3 - Filter out genres that map to an empty string in tree when
+        # keep_existing is enabled and no Last.fm results are found
+        (
+            {
+                "force": True,
+                "keep_existing": True,
+                "source": "track",
+                "whitelist": False,
+                "fallback": "fallback genre",
+                "canonical": True,
+                "prefer_specific": False,
+            },
+            "blacklisted genre",
+            {
+                "track": None,
+                "album": None,
+                "artist": None,
+            },
+            ("fallback genre", "fallback"),
+        ),
         # 8 - fallback to fallback if no original
         (
             {