server read_attribute_value (#524)

* init

* Update internal_server.py

* cleanup

* Update internal_server.py

* Update server.py

* add test

* Update test_server.py

asyncua/server/internal_server.py

@@ -291,6 +291,12 @@ class InternalServer:
         """
         await self.aspace.write_attribute_value(nodeid, attr, datavalue)
 
+    def read_attribute_value(self, nodeid, attr=ua.AttributeIds.Value):
+        """
+        directly read datavalue of the Attribute
+        """
+        return self.aspace.read_attribute_value(nodeid, attr)  
+
     def set_user_manager(self, user_manager):
         """
         set up a function which that will check for authorize users. Input function takes username

asyncua/server/server.py

@@ -669,3 +669,9 @@ class Server:
         so it is a little faster
         """
         return await self.iserver.write_attribute_value(nodeid, datavalue, attr)
+
+    def read_attribute_value(self, nodeid, attr=ua.AttributeIds.Value):
+        """
+        directly read datavalue of the Attribute
+        """
+        return self.iserver.read_attribute_value(nodeid, attr)

tests/test_server.py

@@ -653,6 +653,15 @@ async def check_custom_type(ntype, base_type, server: Server, node_class=None):
     assert await ntype.get_child("2:PropertyString") in properties
     assert (await(await ntype.get_child("2:PropertyString")).read_data_value()).Value.VariantType == ua.VariantType.String
 
+async def test_server_read_write_attribute_value(server: Server):
+    node = await server.get_objects_node().add_variable(0, "0:TestVar", 0, varianttype=ua.VariantType.Int64)
+    dv = server.read_attribute_value(node.nodeid, attr=ua.AttributeIds.Value)
+    assert dv.Value.Value == 0
+    dv = ua.DataValue(Value=ua.Variant(Value=5, VariantType=ua.VariantType.Int64))
+    await server.write_attribute_value(node.nodeid, dv, attr=ua.AttributeIds.Value)
+    dv = server.read_attribute_value(node.nodeid, attr=ua.AttributeIds.Value)
+    assert dv.Value.Value == 5
+    await server.delete_nodes([node])
 
 """
 class TestServerCaching(unittest.TestCase):