Fixed map_field embedded db_field bug

fixes hmarr/mongoengine#512

docs/changelog.rst

@@ -4,6 +4,7 @@ Changelog
 
 Changes in 0.6.X
 ================
+- Fixed map_field embedded db_field issue
 - Fixed .save() _delta issue with DbRefs
 - Fixed Django TestCase
 - Added cmp to Embedded Document

mongoengine/queryset.py

@@ -620,6 +620,7 @@ class QuerySet(object):
                         "Can't use index on unsubscriptable field (%s)" % err)
                 fields.append(field_name)
                 continue
+
             if field is None:
                 # Look up first field from the document
                 if field_name == 'pk':
@@ -637,8 +638,11 @@ class QuerySet(object):
                 from mongoengine.fields import ReferenceField, GenericReferenceField
                 if isinstance(field, (ReferenceField, GenericReferenceField)):
                     raise InvalidQueryError('Cannot perform join in mongoDB: %s' % '__'.join(parts))
-                # Look up subfield on the previous field
-                new_field = field.lookup_member(field_name)
+                if getattr(field, 'field', None):
+                    new_field = field.field.lookup_member(field_name)
+                else:
+                   # Look up subfield on the previous field
+                    new_field = field.lookup_member(field_name)
                 from base import ComplexBaseField
                 if not new_field and isinstance(field, ComplexBaseField):
                     fields.append(field_name)

tests/test_fields.py

@@ -913,6 +913,48 @@ class FieldTest(unittest.TestCase):
 
         Extensible.drop_collection()
 
+    def test_embedded_mapfield_db_field(self):
+
+        class Embedded(EmbeddedDocument):
+            number = IntField(default=0, db_field='i')
+
+        class Test(Document):
+            my_map = MapField(field=EmbeddedDocumentField(Embedded), db_field='x')
+
+        Test.drop_collection()
+
+        test = Test()
+        test.my_map['DICTIONARY_KEY'] = Embedded(number=1)
+        test.save()
+
+        Test.objects.update_one(inc__my_map__DICTIONARY_KEY__number=1)
+
+        test = Test.objects.get()
+        self.assertEqual(test.my_map['DICTIONARY_KEY'].number, 2)
+        doc = self.db.test.find_one()
+        self.assertEqual(doc['x']['DICTIONARY_KEY']['i'], 2)
+
+    def test_embedded_db_field(self):
+
+        class Embedded(EmbeddedDocument):
+            number = IntField(default=0, db_field='i')
+
+        class Test(Document):
+            embedded = EmbeddedDocumentField(Embedded, db_field='x')
+
+        Test.drop_collection()
+
+        test = Test()
+        test.embedded = Embedded(number=1)
+        test.save()
+
+        Test.objects.update_one(inc__embedded__number=1)
+
+        test = Test.objects.get()
+        self.assertEqual(test.embedded.number, 2)
+        doc = self.db.test.find_one()
+        self.assertEqual(doc['x']['i'], 2)
+
     def test_embedded_document_validation(self):
         """Ensure that invalid embedded documents cannot be assigned to
         embedded document fields.