From 2420b5e937d29b93ba2a5bc9d464c8367bcdde0c Mon Sep 17 00:00:00 2001
From: Ross Lawley <ross.lawley@gmail.com>
Date: Wed, 1 Aug 2012 15:14:56 +0100
Subject: [PATCH] Fixed MapField lookup for fields without declared lookups
 (MongoEngine/mongoengine#46)

---
 docs/changelog.rst      |  1 +
 mongoengine/queryset.py |  2 +-
 tests/test_fields.py    | 13 +++++++++++++
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index f5f1dfd9..1f52dfd4 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -5,6 +5,7 @@ Changelog
 Changes in 0.6.X
 ================
 
+- Fixed MapField lookup for fields without declared lookups (MongoEngine/mongoengine#46)
 - Fixed BinaryField python value issue (MongoEngine/mongoengine#48)
 - Fixed SequenceField non numeric value lookup (MongoEngine/mongoengine#41)
 - Fixed queryset manager issue (MongoEngine/mongoengine#52)
diff --git a/mongoengine/queryset.py b/mongoengine/queryset.py
index 15c768dd..b7453c6a 100644
--- a/mongoengine/queryset.py
+++ b/mongoengine/queryset.py
@@ -641,7 +641,7 @@ class QuerySet(object):
                 from mongoengine.fields import ReferenceField, GenericReferenceField
                 if isinstance(field, (ReferenceField, GenericReferenceField)):
                     raise InvalidQueryError('Cannot perform join in mongoDB: %s' % '__'.join(parts))
-                if getattr(field, 'field', None):
+                if hasattr(getattr(field, 'field', None), 'lookup_member'):
                     new_field = field.field.lookup_member(field_name)
                 else:
                    # Look up subfield on the previous field
diff --git a/tests/test_fields.py b/tests/test_fields.py
index 29f5fe97..d3430031 100644
--- a/tests/test_fields.py
+++ b/tests/test_fields.py
@@ -929,6 +929,19 @@ class FieldTest(unittest.TestCase):
         doc = self.db.test.find_one()
         self.assertEqual(doc['x']['DICTIONARY_KEY']['i'], 2)
 
+    def test_map_field_lookup(self):
+        """Ensure MapField lookups succeed on Fields without a lookup method"""
+
+        class Log(Document):
+            name = StringField()
+            visited = MapField(DateTimeField())
+
+        Log.drop_collection()
+        Log(name="wilson", visited={'friends': datetime.now()}).save()
+
+        self.assertEqual(1, Log.objects(
+                                visited__friends__exists=True).count())
+
     def test_embedded_db_field(self):
 
         class Embedded(EmbeddedDocument):