Recursively create mongo query for embeddeddocument elemMatch

docs/changelog.rst

@@ -11,6 +11,7 @@ Changes in 0.10.1 - DEV
 - Fix Document.reload for DynamicDocument. #1050
 - StrictDict & SemiStrictDict are shadowed at init time. #1105
 - Remove test dependencies (nose and rednose) from install dependencies list. #1079
+- Recursively build query when using elemMatch operator. #1130
 
 Changes in 0.10.0
 =================

mongoengine/queryset/transform.py

@@ -26,12 +26,12 @@ MATCH_OPERATORS = (COMPARISON_OPERATORS + GEO_OPERATORS +
                    STRING_OPERATORS + CUSTOM_OPERATORS)
 
 
-def query(_doc_cls=None, **query):
+def query(_doc_cls=None, **kwargs):
     """Transform a query from Django-style format to Mongo format.
     """
     mongo_query = {}
     merge_query = defaultdict(list)
-    for key, value in sorted(query.items()):
+    for key, value in sorted(kwargs.items()):
         if key == "__raw__":
             mongo_query.update(value)
             continue
@@ -105,11 +105,16 @@ def query(_doc_cls=None, **query):
         if op:
             if op in GEO_OPERATORS:
                 value = _geo_operator(field, op, value)
-            elif op in CUSTOM_OPERATORS:
-                if op in ('elem_match', 'match'):
+            elif op in ('match', 'elemMatch'):
+                ListField = _import_class('ListField')
+                EmbeddedDocumentField = _import_class('EmbeddedDocumentField')
+                if (isinstance(value, dict) and isinstance(field, ListField) and
+                    isinstance(field.field, EmbeddedDocumentField)):
+                    value = query(field.field.document_type, **value)
+                else:
                     value = field.prepare_query_value(op, value)
                 value = {"$elemMatch": value}
-                else:
+            elif op in CUSTOM_OPERATORS:
                 NotImplementedError("Custom method '%s' has not "
                                     "been implemented" % op)
             elif op not in STRING_OPERATORS:

tests/queryset/queryset.py

@@ -4116,6 +4116,15 @@ class QuerySetTest(unittest.TestCase):
         ak = list(Bar.objects(foo__match=Foo(shape="square", color="purple")))
         self.assertEqual([b1], ak)
 
+        ak = list(
+            Bar.objects(foo__elemMatch={'shape': "square", "color__exists": True}))
+        self.assertEqual([b1, b2], ak)
+
+        ak = list(
+            Bar.objects(foo__match={'shape': "square", "color__exists": True}))
+        self.assertEqual([b1, b2], ak)
+
+
     def test_upsert_includes_cls(self):
         """Upserts should include _cls information for inheritable classes
         """