From f96e68cd11c72ab321bc1b7923bdfffd29f3bb11 Mon Sep 17 00:00:00 2001
From: Ashley Whetter <ashley.whetter@aardman.com>
Date: Tue, 10 Nov 2015 15:02:19 +0000
Subject: [PATCH] Made type inheritance a validation check for abstract
 references

---
 mongoengine/fields.py  |  8 ++++++++
 tests/fields/fields.py | 25 +++++++++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/mongoengine/fields.py b/mongoengine/fields.py
index 13538c89..4c8c8498 100644
--- a/mongoengine/fields.py
+++ b/mongoengine/fields.py
@@ -996,6 +996,14 @@ class ReferenceField(BaseField):
             self.error('You can only reference documents once they have been '
                        'saved to the database')
 
+        if self.document_type._meta.get('abstract') and \
+                not isinstance(value, self.document_type):
+            self.error('%s is not an instance of abstract reference'
+                    ' type %s' % (value._class_name,
+                        self.document_type._class_name)
+                    )
+
+
     def lookup_member(self, member_name):
         return self.document_type._fields.get(member_name)
 
diff --git a/tests/fields/fields.py b/tests/fields/fields.py
index 860a5749..15daecb9 100644
--- a/tests/fields/fields.py
+++ b/tests/fields/fields.py
@@ -2331,6 +2331,31 @@ class FieldTest(unittest.TestCase):
         Sister.drop_collection()
         Brother.drop_collection()
 
+    def test_abstract_reference_base_type(self):
+        """Ensure that an an abstract reference fails validation when given a
+        Document that does not inherit from the abstract type.
+        """
+        class Sibling(Document):
+            name = StringField()
+            meta = {"abstract": True}
+
+        class Brother(Sibling):
+            sibling = ReferenceField(Sibling)
+
+        class Mother(Document):
+            name = StringField()
+
+        Brother.drop_collection()
+        Mother.drop_collection()
+
+        mother = Mother(name="Carol")
+        mother.save()
+        brother = Brother(name="Bob", sibling=mother)
+        self.assertRaises(ValidationError, brother.save)
+
+        Brother.drop_collection()
+        Mother.drop_collection()
+
     def test_generic_reference(self):
         """Ensure that a GenericReferenceField properly dereferences items.
         """