Use SaveConditionError instead of OperationError in save_condition

docs/changelog.rst

@@ -7,6 +7,7 @@ Changes in 0.10.1 - DEV
 - Fix infinite recursion with CASCADE delete rules under specific conditions. #1046
 - Fix CachedReferenceField bug when loading cached docs as DBRef but failing to save them. #1047
 - Fix ignored chained options #842
+- Document save's save_condition error raises `SaveConditionError` exception #1070
 
 Changes in 0.10.0
 =================

mongoengine/document.py

@@ -16,7 +16,8 @@
     ALLOW_INHERITANCE,
     get_document
 )
-from mongoengine.errors import InvalidQueryError, InvalidDocumentError
+from mongoengine.errors import (InvalidQueryError, InvalidDocumentError,
+                                SaveConditionError)
 from mongoengine.python_support import IS_PYMONGO_3
 from mongoengine.queryset import (OperationError, NotUniqueError,
                                   QuerySet, transform)
@@ -294,6 +295,8 @@ def save(self, force_insert=False, validate=True, clean=True,
             if the condition is satisfied in the current db record.
         .. versionchanged:: 0.10
             :class:`OperationError` exception raised if save_condition fails.
+        .. versionchanged:: 0.10.1
+            :class: save_condition failure now raises a `SaveConditionError`
         """
         signals.pre_save.send(self.__class__, document=self)
 
@@ -359,8 +362,8 @@ def is_new_object(last_error):
                     last_error = collection.update(select_dict, update_query,
                                                    upsert=upsert, **write_concern)
                     if not upsert and last_error['nModified'] == 0:
-                        raise OperationError('Race condition preventing'
-                                             ' document update detected')
+                        raise SaveConditionError('Race condition preventing'
+                                                 ' document update detected')
                     created = is_new_object(last_error)
 
             if cascade is None:

mongoengine/errors.py

@@ -41,6 +41,10 @@ class NotUniqueError(OperationError):
     pass
 
 
+class SaveConditionError(OperationError):
+    pass
+
+
 class FieldDoesNotExist(Exception):
     """Raised when trying to set a field
     not declared in a :class:`~mongoengine.Document`

tests/document/instance.py

@@ -17,7 +17,7 @@
 from mongoengine import *
 from mongoengine.errors import (NotRegistered, InvalidDocumentError,
                                 InvalidQueryError, NotUniqueError,
-                                FieldDoesNotExist)
+                                FieldDoesNotExist, SaveConditionError)
 from mongoengine.queryset import NULLIFY, Q
 from mongoengine.connection import get_db
 from mongoengine.base import get_document
@@ -1021,7 +1021,7 @@ def UUID(i):
         flip(w1)
         self.assertTrue(w1.toggle)
         self.assertEqual(w1.count, 1)
-        self.assertRaises(OperationError,
+        self.assertRaises(SaveConditionError,
             w1.save, save_condition={'save_id': UUID(42)})
         w1.reload()
         self.assertFalse(w1.toggle)
@@ -1050,7 +1050,7 @@ def UUID(i):
         self.assertEqual(w1.count, 2)
         flip(w2)
         flip(w2)
-        self.assertRaises(OperationError,
+        self.assertRaises(SaveConditionError,
             w2.save, save_condition={'save_id': old_id})
         w2.reload()
         self.assertFalse(w2.toggle)
@@ -1063,7 +1063,7 @@ def UUID(i):
         self.assertTrue(w1.toggle)
         self.assertEqual(w1.count, 3)
         flip(w1)
-        self.assertRaises(OperationError,
+        self.assertRaises(SaveConditionError,
             w1.save, save_condition={'count__gte': w1.count})
         w1.reload()
         self.assertTrue(w1.toggle)