lastgenre: remove duplicate genres

beetsplug/lastgenre/__init__.py

@@ -197,6 +197,15 @@ class LastGenrePlugin(plugins.BeetsPlugin):
                 if len(tags_all) >= count:
                     break
             tags = tags_all
+
+        def remove_duplicates(seq):
+            """Remove duplicates from sequence wile preserving order"""
+            seen = set()
+            seen_add = seen.add
+            return [ x for x in seq if x not in seen and not seen_add(x)]
+
+        tags = remove_duplicates(tags)
+
         # c14n only adds allowed genres but we may have had forbidden genres in
         # the original tags list
         tags = [x.title() for x in tags if self._is_allowed(x)]

test/test_lastgenre.py

@@ -129,6 +129,13 @@ class LastGenrePluginTest(unittest.TestCase, TestHelper):
         self.assertEqual(self.plugin._resolve_genres(['iota blues']),
                          '')
 
+    def test_no_duplicate(self):
+        """Remove duplicated genres.
+        """
+        self._setup_config(count=99)
+        self.assertEqual(self.plugin._resolve_genres(['blues', 'blues']),
+                         'Blues')
+
 
 def suite():
     return unittest.TestLoader().loadTestsFromName(__name__)