Reading a predefined structure

[br-iosb]

Hi Everyone,

as in https://github.com/FreeOpcUa/python-opcua/blob/master/tests/tests_enum_struct.py, it is possible to import a NodeSet and register an extension object for a Structure Type, then writing values.

But what about reading/importing predefined structure instances?

I have added a NodeSet "enum_struct_test_readpredefined.xml" and import it AFTER importing and registering the extension class for "enum_struct_test_nodes.xml".
At the end I want this predefined structure loaded and accessible for UA Clients:

        <Value>
            <uax:ExtensionObject>
                <uax:TypeId>
                    <uax:Identifier>ns=2;i=5002</uax:Identifier>
                </uax:TypeId>
                <uax:Body>
                    <ExampleStruct xmlns="http://yourorganisation.org/struct_enum_example/Types.xsd">
                        <IntVal1>99</IntVal1>
                        <EnumVal>EnumVal1_0</EnumVal>
                        <!-- maybe the enum representation is not as expected, but this is the output of UaModeler, maybe fix with: "<EnumVal>0</EnumVal>"?-->
                    </ExampleStruct>
                </uax:Body>
            </uax:ExtensionObject>
        </Value>

I have tried it but it seems like it is not supported at all.
I debugged with my mediocre python skills and added some possible fixes e.g.
setattr(uatypes.VariantType, 'ExampleEnum', ExampleEnum)
but one fix leads to another issue...

Can someone tell me if this has ever been tried and how it should look like?

NodeSet and Code Examples in the ZIP file:
nodesets.zip

[zerox1212]

I'm not following what you are trying to do... You register your extension object, then import XML that has nodes using this extension object with values, but it isn't importing?

Example code would be useful here.

[zerox1212]

What is the output? Is there an exception or stack trace?

[br-iosb]

failure adding node NodeData(nodeid:NumericNodeId(ns=1;i=6001))
Traceback (most recent call last):
  File "c:/Users/xyz/workspace/test_readpredefined.py", line 51, in <module>
    add_server_custom_enum_struct(server)
  File "c:/Users/xyz/workspace/test_readpredefined.py", line 44, in add_server_custom_enum_struct      
    server.import_xml("nodesets/enum_struct_test_readpredefined.xml")
  File "C:\Users\xyz\AppData\Local\Programs\Python\Python38-32\lib\site-packages\opcua\server\server.py", line 518, in import_xml    
    return importer.import_xml(path, xmlstring)
  File "C:\Users\xyz\AppData\Local\Programs\Python\Python38-32\lib\site-packages\opcua\common\xmlimporter.py", line 68, in import_xml
    node = self._add_node_data(nodedata)
  File "C:\Users\xyz\AppData\Local\Programs\Python\Python38-32\lib\site-packages\opcua\common\xmlimporter.py", line 87, in _add_node_data
    node = self.add_variable(nodedata)
  File "C:\Users\xyz\AppData\Local\Programs\Python\Python38-32\lib\site-packages\opcua\common\xmlimporter.py", line 208, in add_variable
    attrs.Value = self._add_variable_value(obj,)
  File "C:\Users\xyz\AppData\Local\Programs\Python\Python38-32\lib\site-packages\opcua\common\xmlimporter.py", line 306, in _add_variable_value
    extobj = self._make_ext_obj(obj.value)
  File "C:\Users\xyz\AppData\Local\Programs\Python\Python38-32\lib\site-packages\opcua\common\xmlimporter.py", line 245, in _make_ext_obj
    self._set_attr(ext, attname, v)
  File "C:\Users\xyz\AppData\Local\Programs\Python\Python38-32\lib\site-packages\opcua\common\xmlimporter.py", line 259, in _set_attr
    pval = xmlparser.ua_type_to_python(val, self._get_val_type(obj, attname))
  File "C:\Users\xyz\AppData\Local\Programs\Python\Python38-32\lib\site-packages\opcua\common\xmlparser.py", line 21, in ua_type_to_python
    return ua_utils.string_to_val(val, getattr(ua.VariantType, uatype_as_str))
  File "C:\Users\xyz\AppData\Local\Programs\Python\Python38-32\lib\site-packages\opcua\common\ua_utils.py", line 133, in string_to_val
    raise NotImplementedError
NotImplementedError

[br-iosb]

and if you do not call setattr(uatypes.VariantType, 'ExampleEnum', ExampleEnum)

failure adding node NodeData(nodeid:NumericNodeId(ns=1;i=6001))
Traceback (most recent call last):
  File "c:/Users/xyz/workspace/test_readpredefined.py", line 51, in <module>
    add_server_custom_enum_struct(server)
  File "c:/Users/xyz/workspace/test_readpredefined.py", line 44, in add_server_custom_enum_struct
    server.import_xml("nodesets/enum_struct_test_readpredefined.xml")
  File "C:\Users\xyz\AppData\Local\Programs\Python\Python38-32\lib\site-packages\opcua\server\server.py", line 518, in import_xml
    return importer.import_xml(path, xmlstring)
  File "C:\Users\xyz\AppData\Local\Programs\Python\Python38-32\lib\site-packages\opcua\common\xmlimporter.py", line 68, in import_xml
    node = self._add_node_data(nodedata)
  File "C:\Users\xyz\AppData\Local\Programs\Python\Python38-32\lib\site-packages\opcua\common\xmlimporter.py", line 87, in _add_node_data
    node = self.add_variable(nodedata)
  File "C:\Users\xyz\AppData\Local\Programs\Python\Python38-32\lib\site-packages\opcua\common\xmlimporter.py", line 208, in add_variable
    attrs.Value = self._add_variable_value(obj,)
  File "C:\Users\xyz\AppData\Local\Programs\Python\Python38-32\lib\site-packages\opcua\common\xmlimporter.py", line 306, in _add_variable_value
    extobj = self._make_ext_obj(obj.value)
  File "C:\Users\xyz\AppData\Local\Programs\Python\Python38-32\lib\site-packages\opcua\common\xmlimporter.py", line 245, in _make_ext_obj
    self._set_attr(ext, attname, v)
  File "C:\Users\xyz\AppData\Local\Programs\Python\Python38-32\lib\site-packages\opcua\common\xmlimporter.py", line 259, in _set_attr
    pval = xmlparser.ua_type_to_python(val, self._get_val_type(obj, attname))
  File "C:\Users\xyz\AppData\Local\Programs\Python\Python38-32\lib\site-packages\opcua\common\xmlparser.py", line 21, in ua_type_to_python
    return ua_utils.string_to_val(val, getattr(ua.VariantType, uatype_as_str))
  File "C:\Users\xyz\AppData\Local\Programs\Python\Python38-32\lib\enum.py", line 346, in __getattr__
    raise AttributeError(name) from None
AttributeError: ExampleEnum

[zerox1212]

Would need to debug the XML stuff, which is very difficult. Can you create your node that uses the extension object from code instead of XML import to see if it works that way?

[br-iosb]

Technically yes, this is possible, as shown in https://github.com/FreeOpcUa/python-opcua/blob/master/tests/tests_enum_struct.py.

edit: I just noticed that the link was broken and updated it...

[br-iosb]

So far no updates?
Should i open an issue or is this more like a new feature?