Fixes cascading saves with filefields

fixes MongoEngine#24 MongoEngine#25

docs/changelog.rst

@@ -2,6 +2,10 @@
 Changelog
 =========
 
+Changes in 0.6.X
+================
+- Fixed recursive save with FileField
+
 Changes in 0.6.10
 =================
 - Fixed basedict / baselist to return super(..)

mongoengine/fields.py

@@ -889,6 +889,13 @@ def __getstate__(self):
         self_dict['_fs'] = None
         return self_dict
 
+    def __repr__(self):
+        return '<%s: %s>' % (self.__class__.__name__, self.grid_id)
+
+    def __cmp__(self, other):
+        return cmp((self.grid_id, self.collection_name, self.db_alias),
+                   (other.grid_id, other.collection_name, other.db_alias))
+
     @property
     def fs(self):
         if not self._fs:

tests/test_document.py

@@ -1335,7 +1335,7 @@ def test_save_max_recursion_not_hit_with_file_field(self):
 
         class Foo(Document):
             name = StringField()
-            file = FileField()
+            picture = FileField()
             bar = ReferenceField('self')
 
         Foo.drop_collection()
@@ -1344,7 +1344,7 @@ class Foo(Document):
         a.save()
 
         a.bar = a
-        a.file = open(TEST_IMAGE_PATH, 'rb')
+        a.picture = open(TEST_IMAGE_PATH, 'rb')
         a.save()
 
         # Confirm can save and it resets the changed fields without hitting
@@ -1353,7 +1353,7 @@ class Foo(Document):
         b.name='world'
         b.save()
 
-        self.assertEquals(b.file, b.bar.file, b.bar.bar.file)
+        self.assertEquals(b.picture, b.bar.picture, b.bar.bar.picture)
 
     def test_save_cascades(self):