fix-#744: Querying by a field defined in a subclass raises InvalidQueryError

docs/changelog.rst

@@ -5,6 +5,7 @@ Changelog
 
 Changes in 0.9.X - DEV
 ======================
+- Querying by a field defined in a subclass raises InvalidQueryError #744
 - Add Support For MongoDB 2.6.X's maxTimeMS #778
 - abstract shouldn't be inherited in EmbeddedDocument # 789
 - Allow specifying the '_cls' as a field for indexes #397

mongoengine/base/document.py

@@ -884,6 +884,19 @@ class BaseDocument(object):
                 elif cls._dynamic:
                     DynamicField = _import_class('DynamicField')
                     field = DynamicField(db_field=field_name)
+                elif cls._meta.get("allow_inheritance", False) or cls._meta.get("abstract", False):
+                    # 744: in case the field is defined in a subclass
+                    field = None
+                    for subcls in cls.__subclasses__():
+                        try:
+                            field = subcls._lookup_field([field_name])[0]
+                        except LookUpError:
+                            continue
+
+                        if field is not None:
+                            break
+                    else:
+                        raise LookUpError('Cannot resolve field "%s"' % field_name)
                 else:
                     raise LookUpError('Cannot resolve field "%s"'
                                       % field_name)

tests/queryset/queryset.py

@@ -4405,6 +4405,23 @@ class QuerySetTest(unittest.TestCase):
         # 778: max_time_ms can get only int or None as input
         self.assertRaises(TypeError, self.Person.objects(name="name").max_time_ms, "not a number")
 
+    def test_subclass_field_query(self):
+        class Animal(Document):
+            is_mamal = BooleanField()
+            meta = dict(allow_inheritance=True)
+
+        class Cat(Animal):
+            whiskers_length = FloatField()
+
+        class ScottishCat(Cat):
+            folded_ears = BooleanField()
+
+        Animal(is_mamal=False).save()
+        Cat(is_mamal=True, whiskers_length=5.1).save()
+        ScottishCat(is_mamal=True, folded_ears=True).save()
+        self.assertEquals(Animal.objects(folded_ears=True).count(), 1)
+        self.assertEquals(Animal.objects(whiskers_length=5.1).count(), 1)
+
 
 if __name__ == '__main__':
     unittest.main()