Delete tags from media files

beets/mediafile.py

@@ -342,8 +342,9 @@ class StorageStyle(object):
     describe more sophisticated translations or format-specific access
     strategies.
 
-    MediaFile uses a StorageStyle via two methods: ``get()`` and
-    ``set()``. It passes a Mutagen file object to each.
+    MediaFile uses a StorageStyle via three methods: ``get()``,
+    ``set()``, and ``delete()``. It passes a Mutagen file object to
+    each.
 
     Internally, the StorageStyle implements ``get()`` and ``set()``
     using two steps that may be overridden by subtypes. To get a value,
@@ -447,6 +448,12 @@ class StorageStyle(object):
 
         return value
 
+    def delete(self, mutagen_file):
+        """Remove the tag from the file.
+        """
+        if self.key in mutagen_file:
+            del mutagen_file[self.key]
+
 
 class ListStorageStyle(StorageStyle):
     """Abstract storage style that provides access to lists.
@@ -572,6 +579,12 @@ class MP4TupleStorageStyle(MP4StorageStyle):
         items[self.index] = int(value)
         self.store(mutagen_file, items)
 
+    def delete(self, mutagen_file):
+        if self.index == 0:
+            super(MP4TupleStorageStyle, self).delete(mutagen_file)
+        else:
+            self.set(mutagen_file, None)
+
 
 class MP4ListStorageStyle(ListStorageStyle, MP4StorageStyle):
     pass
@@ -725,6 +738,15 @@ class MP3DescStorageStyle(MP3StorageStyle):
                 except IndexError:
                     return None
 
+    def delete(self, mutagen_file):
+        frame = None
+        for frame in mutagen_file.tags.getall(self.key):
+            if frame.desc.lower() == self.description.lower():
+                break
+        if frame is not None:
+            del mutagen_file[frame.HashKey]
+
+
 
 class MP3SlashPackStorageStyle(MP3StorageStyle):
     """Store value as part of pair that is serialized as a slash-
@@ -752,6 +774,12 @@ class MP3SlashPackStorageStyle(MP3StorageStyle):
             items.pop()  # Do not store last value
         self.store(mutagen_file, '/'.join(map(unicode, items)))
 
+    def delete(self, mutagen_file):
+        if self.pack_pos == 0:
+            super(MP3SlashPackStorageStyle, self).delete(mutagen_file)
+        else:
+            self.set(mutagen_file, None)
+
 
 class MP3ImageStorageStyle(ListStorageStyle, MP3StorageStyle):
     """Converts between APIC frames and ``Image`` instances.
@@ -943,6 +971,10 @@ class MediaField(object):
             value = self._none_value()
         for style in self.styles(mediafile.mgfile):
             style.set(mediafile.mgfile, value)
+    
+    def __delete__(self, mediafile):
+        for style in self.styles(mediafile.mgfile):
+            style.delete(mediafile.mgfile)
 
     def _none_value(self):
         """Get an appropriate "null" value for this field's type. This
@@ -1083,6 +1115,9 @@ class DateItemField(MediaField):
         items[self.item_pos] = value
         self.date_field._set_date_tuple(mediafile, *items)
 
+    def __delete__(self, mediafile):
+        self.__set__(mediafile, None)
+
 
 class CoverArtField(MediaField):
     """A descriptor that provides access to the *raw image data* for the

test/test_mediafile.py

@@ -580,6 +580,34 @@ class ReadWriteTestBase(ArtTestMixin, GenreListTestMixin,
         self.assertEqual(mediafile.year, 0)
         self.assertEqual(mediafile.date, datetime.date.min)
 
+    def test_delete_tag(self):
+        mediafile = self._mediafile_fixture('full')
+
+        keys = self.full_initial_tags.keys()
+        keys.remove('art')
+        for key in keys:
+            self.assertIsNotNone(getattr(mediafile, key))
+            delattr(mediafile, key)
+
+        mediafile.save()
+        mediafile = MediaFile(mediafile.path)
+
+        # TODO Eventually the tags should have None values
+        empty_tags = dict((k, v) for k, v in self.empty_tags.items()
+                                 if k in keys)
+        self.assertTags(mediafile, empty_tags)
+
+    def test_delete_packed_total(self):
+        mediafile = self._mediafile_fixture('full')
+
+        delattr(mediafile, 'tracktotal')
+        delattr(mediafile, 'disctotal')
+
+        mediafile.save()
+        mediafile = MediaFile(mediafile.path)
+        self.assertEqual(mediafile.track, self.full_initial_tags['track'])
+        self.assertEqual(mediafile.disc, self.full_initial_tags['disc'])
+
     def assertTags(self, mediafile, tags):
         errors = []
         for key, value in tags.items():