Added Reverse option to SortedLists

Thanks Stephen Young for the patch
closes #364

AUTHORS

@@ -77,3 +77,4 @@ that much better:
  * jpfarias
  * jonrscott
  * Alice Zoë Bevan-McGregor
+ * Stephen Young

docs/changelog.rst

@@ -5,6 +5,7 @@ Changelog
 Changes in dev
 ==============
 
+- Added reverse option to SortedListFields
 - Fixed dereferencing - multi directional list dereferencing
 - Fixed issue creating indexes with recursive embedded documents
 - Fixed recursive lookup in _unique_with_indexes

mongoengine/fields.py

@@ -511,20 +511,24 @@ class SortedListField(ListField):
     retrieved.
 
     .. versionadded:: 0.4
+    .. versionchanged:: 0.6 - added reverse keyword
     """
 
     _ordering = None
+    _order_reverse = False
 
     def __init__(self, field, **kwargs):
         if 'ordering' in kwargs.keys():
             self._ordering = kwargs.pop('ordering')
+        if 'reverse' in kwargs.keys():
+            self._order_reverse = kwargs.pop('reverse')
         super(SortedListField, self).__init__(field, **kwargs)
 
     def to_mongo(self, value):
         value = super(SortedListField, self).to_mongo(value)
         if self._ordering is not None:
-            return sorted(value, key=itemgetter(self._ordering))
+            return sorted(value, key=itemgetter(self._ordering), reverse=self._order_reverse)
-        return sorted(value)
+        return sorted(value, reverse=self._order_reverse)
 
 
 class DictField(ComplexBaseField):

tests/fields.py

@@ -481,6 +481,31 @@ class FieldTest(unittest.TestCase):
 
         BlogPost.drop_collection()
 
+    def test_reverse_list_sorting(self):
+        '''Ensure that a reverse sorted list field properly sorts values'''
+
+        class Category(EmbeddedDocument):
+            count = IntField()
+            name = StringField()
+
+        class CategoryList(Document):
+            categories = SortedListField(EmbeddedDocumentField(Category), ordering='count', reverse=True)
+            name = StringField()
+
+        catlist = CategoryList(name="Top categories")
+        cat1 = Category(name='posts', count=10)
+        cat2 = Category(name='food', count=100)
+        cat3 = Category(name='drink', count=40)
+        catlist.categories = [cat1, cat2, cat3]
+        catlist.save()
+        catlist.reload()
+
+        self.assertEqual(catlist.categories[0].name, cat2.name)
+        self.assertEqual(catlist.categories[1].name, cat3.name)
+        self.assertEqual(catlist.categories[2].name, cat1.name)
+
+        CategoryList.drop_collection()
+
     def test_list_field(self):
         """Ensure that list types work as expected.
         """