Allow removing an entity from metadata

arkindex/documents/serializers/elements.py

@@ -35,7 +35,7 @@ class MetaDataUpdateSerializer(MetaDataLightSerializer):
     """
     Allow editing MetaData
     """
-    entity = serializers.PrimaryKeyRelatedField(queryset=Entity.objects.none(), required=False)
+    entity = serializers.PrimaryKeyRelatedField(queryset=Entity.objects.none(), required=False, allow_null=True)
 
     class Meta:
         model = MetaData

arkindex/documents/tests/test_metadata.py

@@ -467,6 +467,19 @@ class TestMetaData(FixtureAPITestCase):
         metadata.refresh_from_db()
         self.assertEqual(metadata.entity, entity)
 
+    def test_patch_metadata_entity_none(self):
+        self.client.force_login(self.superuser)
+        entity = self.corpus.entities.create(name='Texas', type=EntityType.Location, source=self.source)
+        metadata = self.vol.metadatas.create(type=MetaType.Location, name='location', value='Texas', entity=entity)
+        response = self.client.patch(
+            reverse('api:metadata-edit', kwargs={'pk': str(metadata.id)}),
+            data={'entity': None},
+            format='json'
+        )
+        self.assertEqual(response.status_code, status.HTTP_200_OK, response.json())
+        metadata.refresh_from_db()
+        self.assertIsNone(metadata.entity)
+
     def test_create_metadata_entity_corpus_check(self):
         self.client.force_login(self.superuser)
         entity = self.private_corpus.entities.create(name='Texas', type=EntityType.Location, source=self.source)