Fix serialization of messages when ujson < 1.35 is used (#266)

* add test for serialization of messages

* override __dir__ method for MessageBase to exclude service fields

* add test for dir over message

Author: mzk-vct

plenum/common/messages/message_base.py

@@ -156,3 +156,6 @@ def __hash__(self):
         for index, value in enumerate(list(self.__iter__())):
             h = h * (index + 1) * (hash(value) + 1)
         return h
+
+    def __dir__(self):
+        return self.keys()

plenum/test/input_validation/test_message_serialization.py

@@ -0,0 +1,20 @@
+from plenum.common.messages.node_messages import LedgerStatus
+from stp_zmq.zstack import ZStack
+
+
+def test_that_service_fields_not_being_serialized():
+    """
+    Checks that service fields of validators, like 'typename' and 'schema' ]
+    are excluded from serialized message
+    """
+
+    message = LedgerStatus(1,10,None,None,"AwgQhPR9cgRubttBGjRruCRMLhZFBffbejbPipj7WBBm")
+    serialized = ZStack.serializeMsg(message)
+    deserialized = ZStack.deserializeMsg(serialized)
+    service_fields = {'typename', 'schema', 'optional', 'nullable'}
+    assert service_fields - set(deserialized) == service_fields
+
+
+def test_that_dir_returns_only_message_keys():
+    message = LedgerStatus(1, 10, None, None, "AwgQhPR9cgRubttBGjRruCRMLhZFBffbejbPipj7WBBm")
+    assert set(dir(message)) == set(message.keys())