PICARD-1413: Explicitly mark compilation tag as deleted

Mark compilation tag as deleted if it does not apply instead of sneakily removing it only for ID3.

picard/album.py

@@ -341,6 +341,8 @@ class Album(DataObject, Item):
         artists.add(tm["artist"])
         if va:
             tm["compilation"] = "1"
+        else:
+            tm.delete("compilation")
         if discpregap:
             tm["~discpregap"] = "1"
 

picard/formats/id3.py

@@ -367,7 +367,6 @@ class ID3File(File):
         tmcl = mutagen.id3.TMCL(encoding=encoding, people=[])
         tipl = mutagen.id3.TIPL(encoding=encoding, people=[])
 
-        tags.delall('TCMP')
         for name, values in metadata.rawitems():
             values = [id3text(v, encoding) for v in values]
             name = id3text(name, encoding)

test/test_formats.py

@@ -206,6 +206,16 @@ class CommonTests:
             for tag in self.unsupported_tags:
                 self.assertTrue(tag not in loaded_metadata, '%s: %r != None' % (tag, loaded_metadata[tag]))
 
+        @skipUnlessTestfile
+        def test_preserve_unchanged_tags(self):
+            metadata = Metadata()
+            for (key, value) in self.tags.items():
+                metadata[key] = value
+            save_metadata(self.filename, metadata)
+            loaded_metadata = save_and_load_metadata(self.filename, Metadata())
+            for (key, value) in self.tags.items():
+                self.assertEqual(loaded_metadata[key], value, '%s: %r != %r' % (key, loaded_metadata[key], value))
+
         @skipUnlessTestfile
         def test_delete_simple_tags(self):
             metadata = Metadata()
@@ -480,20 +490,9 @@ class CommonTests:
             self.assertFalse('TXXX:Work' in raw_metadata)
             self.assertTrue('TXXX:WORK' in raw_metadata)
 
-        @skipUnlessTestfile
-        def test_preserve_performance_tags(self):
-            metadata = Metadata()
-            metadata['engineer'] = 'Foo'
-            metadata['performer:drums'] = 'Foo'
-            save_and_load_metadata(self.filename, metadata)
-            new_metadata = save_and_load_metadata(self.filename, Metadata())
-            self.assertEqual('Foo', new_metadata['engineer'])
-            self.assertEqual('Foo', new_metadata['performer:drums'])
-
-        @skipUnlessTestfile
-        def test_preserve_performance_tags_v23(self):
+        def test_preserve_unchanged_tags_v23(self):
             config.setting['write_id3v23'] = True
-            self.test_preserve_performance_tags()
+            self.test_preserve_unchanged_tags()
 
 
 class FLACTest(CommonTests.FormatsTest):