PICARD-2549: Fixed similarity not getting updated if only difference is cover art

If a file is moved to a track where the metadata matches perfectly but only cover art is different, then the similarity score of this file was not recalculated. That means the file retains the similarity of the previous (probably bad) match. Also only do this change if the state was NORMAL before (similar to the other state updates, ignoring states like PENDING and ERROR).

picard/file.py

@@ -710,12 +710,12 @@ class File(QtCore.QObject, Item):
                         self.state = File.CHANGED
                     break
             else:
-                if (self.metadata.images
+                self.similarity = 1.0
+                if self.state in (File.CHANGED, File.NORMAL):
+                    if (self.metadata.images
                         and self.orig_metadata.images != self.metadata.images):
-                    self.state = File.CHANGED
-                else:
-                    self.similarity = 1.0
-                    if self.state == File.CHANGED:
+                        self.state = File.CHANGED
+                    else:
                         self.state = File.NORMAL
         if signal:
             log.debug("Updating file %r", self)

test/test_file.py

@@ -2,7 +2,7 @@
 #
 # Picard, the next-generation MusicBrainz tagger
 #
-# Copyright (C) 2018-2021 Philipp Wolfer
+# Copyright (C) 2018-2022 Philipp Wolfer
 # Copyright (C) 2019-2022 Laurent Monin
 # Copyright (C) 2021 Bob Swift
 # Copyright (C) 2021 Sophist-UK
@@ -459,7 +459,7 @@ class FileUpdateTest(PicardTestCase):
         self.file.state = File.NORMAL
 
         self.file.update(signal=False)
-        self.assertEqual(self.file.similarity, self.INVALIDSIMVAL)  # it shouldbn't be modified
+        self.assertEqual(self.file.similarity, 1.0)
         self.assertEqual(self.file.state, File.CHANGED)
 
     def test_signal(self):