EmbeddedDocument._instance is now set when settng the attribute (#506)

docs/changelog.rst

@@ -4,6 +4,7 @@ Changelog
 
 Changes in 0.8.5
 ================
+- EmbeddedDocument._instance is now set when settng the attribute (#506)
 - Fixed EmbeddedDocument with ReferenceField equality issue (#502)
 - Fixed GenericReferenceField serialization order (#499)
 - Fixed count and none bug (#498)

mongoengine/base/fields.py

@@ -89,12 +89,7 @@ class BaseField(object):
             return self
 
         # Get value from document instance if available
-        value = instance._data.get(self.name)
-
-        EmbeddedDocument = _import_class('EmbeddedDocument')
-        if isinstance(value, EmbeddedDocument) and value._instance is None:
-            value._instance = weakref.proxy(instance)
-        return value
+        return instance._data.get(self.name)
 
     def __set__(self, instance, value):
         """Descriptor for assigning a value to a field in a document.
@@ -116,6 +111,10 @@ class BaseField(object):
                 # Values cant be compared eg: naive and tz datetimes
                 # So mark it as changed
                 instance._mark_as_changed(self.name)
+
+        EmbeddedDocument = _import_class('EmbeddedDocument')
+        if isinstance(value, EmbeddedDocument) and value._instance is None:
+            value._instance = weakref.proxy(instance)
         instance._data[self.name] = value
 
     def error(self, message="", errors=None, field_name=None):

tests/document/instance.py

@@ -490,6 +490,26 @@ class InstanceTest(unittest.TestCase):
         doc = Doc.objects.get()
         self.assertEqual(doc, doc.embedded_field[0]._instance)
 
+    def test_instance_is_set_on_setattr(self):
+
+        class Email(EmbeddedDocument):
+            email = EmailField()
+            def clean(self):
+                print "instance:"
+                print self._instance
+
+        class Account(Document):
+            email = EmbeddedDocumentField(Email)
+
+        Account.drop_collection()
+        acc = Account()
+        acc.email = Email(email='test@example.com')
+        self.assertTrue(hasattr(acc._data["email"], "_instance"))
+        acc.save()
+
+        acc1 = Account.objects.first()
+        self.assertTrue(hasattr(acc1._data["email"], "_instance"))
+
     def test_document_clean(self):
         class TestDocument(Document):
             status = StringField()