--- /dev/null
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements. See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You under the Apache License, Version 2.0
+# (the "License"); you may not use this file except in compliance with
+# the License. You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from ...utils.collections import deepcopy_with_locators
+
+
+class Null(object):
+ """
+ Represents an explicit null value provided by the user, which is different from
+ not supplying a value at all.
+
+ It is a singleton.
+ """
+
+ @property
+ def as_raw(self):
+ return None
+
+NULL = Null()
+
+
+def none_to_null(value):
+ """
+ Convert ``None`` to ``NULL``, recursively.
+ """
+
+ if value is None:
+ return NULL
+ if isinstance(value, list):
+ value = deepcopy_with_locators(value)
+ for i, _ in enumerate(value):
+ value[i] = none_to_null(value[i])
+ elif isinstance(value, dict):
+ value = deepcopy_with_locators(value)
+ for k, v in value.iteritems():
+ value[k] = none_to_null(v)
+ return value
+
+
+def null_to_none(value):
+ """
+ Convert ``NULL`` to ``None``, recursively.
+ """
+
+ if value is NULL:
+ return None
+ if isinstance(value, list):
+ value = deepcopy_with_locators(value)
+ for i, _ in enumerate(value):
+ value[i] = none_to_null(value[i])
+ elif isinstance(value, dict):
+ value = deepcopy_with_locators(value)
+ for k, v in value.iteritems():
+ value[k] = none_to_null(v)
+ return value