Add MediaFile.fields() method

beets/mediafile.py

@@ -1256,6 +1256,14 @@ class MediaFile(object):
             for tag in self.mgfile.keys():
                 del self.mgfile[tag]
 
+    @classmethod
+    def fields(cls):
+        """Yield the names of all properties that are MediaFields.
+        """
+        for property, descriptor in cls.__dict__.items():
+            if isinstance(descriptor, MediaField):
+                yield property
+
 
     # Field definitions.
 

test/test_mediafile.py

@@ -692,6 +692,20 @@ class OpusTest(ReadWriteTestBase, unittest.TestCase):
     }
 
 
+class MediaFieldTest(unittest.TestCase):
+
+    def test_properties_from_fields(self):
+        path = os.path.join(_common.RSRC, 'full.mp3')
+        mediafile = MediaFile(path)
+        for field in MediaFile.fields():
+            self.assertTrue(hasattr(mediafile, field))
+
+    def test_known_fields(self):
+        fields = ReadWriteTestBase.empty_tags.keys()
+        fields.extend(('encoder', 'images', 'genres', 'albumtype'))
+        self.assertItemsEqual(MediaFile.fields(), fields)
+
+
 def suite():
     return unittest.TestLoader().loadTestsFromName(__name__)