Added __basefield__ attribute in VirtualField

Keep track of the base model field from which the VirtualField has been created in the __basefield__ attribute.

django_hstore/virtual.py

@@ -80,11 +80,14 @@ def create_hstore_virtual_field(field_cls, kwargs, hstore_field_name):
         raise ValueError('field must be either a django standard field or a subclass of django.db.models.Field')
 
     class VirtualField(HStoreVirtualMixin, BaseField):
+        # keep basefield info (added for django-rest-framework-hstore)
+        __basefield__ = BaseField
+
         def __init__(self, *args, **kwargs):
             try:
                 self.hstore_field_name = hstore_field_name
             except KeyError:
-                raise ValueError('missing hstore_field_name keyword argument')
+                raise ValueError('missing hstore_field_name keyword argument')    
             super(VirtualField, self).__init__(*args, **kwargs)
 
         def deconstruct(self, *args, **kwargs):

tests/django_hstore_tests/tests.py

@@ -811,6 +811,11 @@ class FakeModel(object):
             virtual_date = SchemaDataBag()._hstore_virtual_fields['date']
 
             self.assertEqual(virtual_date.value_to_string(FakeModel()), '2014-08-08')
+
+        def test_basefield_attribute(self):
+            virtual_field = SchemaDataBag()._hstore_virtual_fields['char']
+            self.assertEqual(virtual_field.__basefield__.__name__, 'CharField')
+
     else:
         def test_improperly_configured(self):            
             with self.assertRaises(ImproperlyConfigured):