Add test for django-widgy-blog behavior which was broken. (And fix it)

tests/core_tests/tests/test_fields.py

@@ -66,6 +66,19 @@ def test_add_root(self):
 
         self.assertEqual(root_node.content.pk, 1337)
 
+    def test_override_add_root(self):
+        """
+        If we put a widgy content before save()ing, the root_node shouldn't be overridden.
+        """
+        instance = HasAWidgy()
+
+        field = HasAWidgy._meta.get_field('widgy')
+        instance.widgy = ContentType.objects.get_for_model(Layout)
+        instance.widgy = field.add_root(instance, {'pk': 1337})
+        instance.save()
+
+        self.assertEqual(instance.widgy.content.pk, 1337)
+
 
 @unittest.skip("We want WidgyFields to work with non-modelforms, but we haven't designed an API yet.")
 class TestPlainForm(TestCase):

widgy/db/fields.py

@@ -37,6 +37,8 @@ def __set__(self, instance, value):
             setattr(instance, self.field.pre_save_ct_field_name, value)
         else:
             super(WidgyFieldObjectDescriptor, self).__set__(instance, value)
+            if hasattr(instance, self.field.pre_save_ct_field_name):
+                delattr(instance, self.field.pre_save_ct_field_name)
 
 
 class WidgyField(models.ForeignKey):