Moved SortedListField stuff into its own branch

mongoengine/fields.py

@@ -1,6 +1,7 @@
 from base import BaseField, ObjectIdField, ValidationError, get_document
 from document import Document, EmbeddedDocument
 from connection import _get_db
+from operator import itemgetter
 
 import re
 import pymongo
@@ -12,7 +13,7 @@ __all__ = ['StringField', 'IntField', 'FloatField', 'BooleanField',
            'DateTimeField', 'EmbeddedDocumentField', 'ListField', 'DictField',
            'ObjectIdField', 'ReferenceField', 'ValidationError',
            'DecimalField', 'URLField', 'GenericReferenceField',
-           'BinaryField']
+           'BinaryField', 'SortedListField']
 
 RECURSIVE_REFERENCE_CONSTANT = 'self'
 
@@ -310,6 +311,23 @@ class ListField(BaseField):
     def lookup_member(self, member_name):
         return self.field.lookup_member(member_name)
 
+class SortedListField(ListField):
+    """A ListField that sorts the contents of its list before writing to
+    the database in order to ensure that a sorted list is always
+    retrieved.
+    """
+
+    _ordering = None
+
+    def __init__(self, field, **kwargs):
+        if 'ordering' in kwargs.keys():
+            self._ordering = kwargs.pop('ordering')
+        super(SortedListField, self).__init__(field, **kwargs)
+
+    def to_mongo(self, value):
+        if self._ordering is not None:
+            return sorted([self.field.to_mongo(item) for item in value], key=itemgetter(self._ordering))
+        return sorted([self.field.to_mongo(item) for item in value])
 
 class DictField(BaseField):
     """A dictionary field that wraps a standard Python dictionary. This is

tests/fields.py

@@ -218,6 +218,37 @@ class FieldTest(unittest.TestCase):
         post.comments = 'yay'
         self.assertRaises(ValidationError, post.validate)
 
+    def test_sorted_list_sorting(self):
+        """Ensure that a sorted list field properly sorts values.
+        """
+        class Comment(EmbeddedDocument):
+            order = IntField()
+            content = StringField()
+
+        class BlogPost(Document):
+            content = StringField()
+            comments = SortedListField(EmbeddedDocumentField(Comment), ordering='order')
+            tags = SortedListField(StringField())
+
+        post = BlogPost(content='Went for a walk today...')
+        post.save()
+
+        post.tags = ['leisure', 'fun']
+        post.save()
+        post.reload()
+        self.assertEqual(post.tags, ['fun', 'leisure'])
+        
+        comment1 = Comment(content='Good for you', order=1)
+        comment2 = Comment(content='Yay.', order=0)
+        comments = [comment1, comment2]
+        post.comments = comments
+        post.save()
+        post.reload()
+        self.assertEqual(post.comments[0].content, comment2.content)
+        self.assertEqual(post.comments[1].content, comment1.content)
+
+        BlogPost.drop_collection()
+
     def test_dict_validation(self):
         """Ensure that dict types work as expected.
         """