Prevent abstract Types from beeing instantiated (#842)

* init

* add: is_abstract check and typehints

* change import for Node

* change import for Node

* remove nodeclass-typehints due to import error

* add test for instantiate abstract type

* edit: change ValueError to UaError

* edit: test

asyncua/common/instantiate_util.py

@@ -4,6 +4,8 @@
 
 import logging
 
+from typing import Union
+
 from asyncua import ua
 from .ua_utils import get_node_supertypes, is_child_present
 from .copy_node_util import _rdesc_from_node, _read_and_copy_attrs
@@ -12,13 +14,22 @@
 logger = logging.getLogger(__name__)
 
 
-async def instantiate(parent, node_type, nodeid=None, bname=None, dname=None, idx=0, instantiate_optional=True):
+async def is_abstract(node_type) -> bool:
+    result = await node_type.read_attribute(ua.AttributeIds.IsAbstract)
+    return result.Value.Value
+
+
+async def instantiate(parent, node_type, nodeid: ua.NodeId=None, bname: Union[str, ua.QualifiedName]=None, dname: ua.LocalizedText=None, idx: int=0, instantiate_optional: bool=True):
     """
     instantiate a node type under a parent node.
     nodeid and browse name of new node can be specified, or just namespace index
     If they exists children of the node type, such as components, variables and
     properties are also instantiated
     """
+    abstract = await is_abstract(node_type)
+    if abstract:
+        raise ua.UaError(f"InstantiationError NodeId: {node_type.nodeid} is abstract and cant be instantiated!")
+
     rdesc = await _rdesc_from_node(parent, node_type)
     rdesc.TypeDefinition = node_type.nodeid
 

tests/test_common.py

@@ -1010,6 +1010,12 @@ async def test_instantiate_string_nodeid(opc):
     await opc.opc.delete_nodes([dev_t])
 
 
+async def test_instantiate_abstract(opc):
+    finit_statemachine_type = opc.opc.get_node("ns=0;i=2771")  # IsAbstract=True
+    with pytest.raises(ua.UaError):
+        node = await instantiate(opc.opc.nodes.objects, finit_statemachine_type, bname="2:TestFiniteStateMachine")
+
+
 async def test_variable_with_datatype(opc):
     v1 = await opc.opc.nodes.objects.add_variable(
         3, 'VariableEnumType1', ua.ApplicationType.ClientAndServer, datatype=ua.NodeId(ua.ObjectIds.ApplicationType)