monkeybeets.yaml

item_fields:
    has_albums: |
        import gc
        from beets import library
        from beetsplug.convert import _fs_lock # Abuse the lock for our purpose

        with _fs_lock:
            if not hasattr(library, '_artists_with_albums'):
                libs = [l for l in gc.get_objects()
                        if isinstance(l, library.Library)]
                if len(libs) != 1:
                    raise Exception('No unique global Library instance found.')

                library._artists_with_albums = set()
                for result in libs[0].albums('album:'):
                    artist_value = result.get('albumartist')
                    if artist_value:
                        library._artists_with_albums.add(artist_value)

            return artist in library._artists_with_albums

paths:
    default: $albumartist/$album%aunique{}/$track. $title
    singleton: %if{$has_albums,$artist/Non-Album/$title,Non-Album/$artist/$title}
    comp: Compilations/$album%aunique{}/$track. $title