Updated slave_okay syntax

Now inline with .timeout() and .snapshot().
Made them chainable - so its easier to use and added tests for cursor_args

mongoengine/queryset.py

@@ -452,7 +452,6 @@ class QuerySet(object):
         self._mongo_query = None
         self._cursor_obj = None
         self._class_check = class_check
-        self._slave_okay = slave_okay
         return self
 
     def filter(self, *q_objs, **query):
@@ -504,18 +503,23 @@ class QuerySet(object):
 
         return self._collection_obj
 
+    @property
+    def _cursor_args(self):
+        cursor_args = {
+            'snapshot': self._snapshot,
+            'timeout': self._timeout,
+            'slave_okay': self._slave_okay
+        }
+        if self._loaded_fields:
+            cursor_args['fields'] = self._loaded_fields.as_dict()
+        return cursor_args
+
     @property
     def _cursor(self):
         if self._cursor_obj is None:
-            cursor_args = {
-                'snapshot': self._snapshot,
-                'timeout': self._timeout,
-                'slave_okay': self._slave_okay
-            }
-            if self._loaded_fields:
-                cursor_args['fields'] = self._loaded_fields.as_dict()
+
             self._cursor_obj = self._collection.find(self._query,
-                                                     **cursor_args)
+                                                     **self._cursor_args)
             # Apply where clauses to cursor
             if self._where_clause:
                 self._cursor_obj.where(self._where_clause)
@@ -772,7 +776,7 @@ class QuerySet(object):
         id_field = self._document._meta['id_field']
         object_id = self._document._fields[id_field].to_mongo(object_id)
 
-        result = self._collection.find_one({'_id': object_id})
+        result = self._collection.find_one({'_id': object_id}, **self._cursor_args)
         if result is not None:
             result = self._document._from_son(result)
         return result
@@ -788,7 +792,8 @@ class QuerySet(object):
         """
         doc_map = {}
 
-        docs = self._collection.find({'_id': {'$in': object_ids}})
+        docs = self._collection.find({'_id': {'$in': object_ids}},
+                                     **self._cursor_args)
         for doc in docs:
             doc_map[doc['_id']] = self._document._from_son(doc)
 
@@ -1085,6 +1090,7 @@ class QuerySet(object):
         :param enabled: whether or not snapshot mode is enabled
         """
         self._snapshot = enabled
+        return self
 
     def timeout(self, enabled):
         """Enable or disable the default mongod timeout when querying.
@@ -1092,6 +1098,15 @@ class QuerySet(object):
         :param enabled: whether or not the timeout is used
         """
         self._timeout = enabled
+        return self
+
+    def slave_okay(self, enabled):
+        """Enable or disable the slave_okay when querying.
+
+        :param enabled: whether or not the slave_okay is enabled
+        """
+        self._slave_okay = enabled
+        return self
 
     def delete(self, safe=False):
         """Delete the documents matched by the query.