Dataclass serializer generation fails in 3.14

[HC4L]

Describe the bug

Using uadiscover or any other method to open a connection to a server.
When creating the serializer for the class asyncua.ua.uaprotocol_hand.Hello a "property" field is included in the fields to create serializers for.
I think there is a change in 3.14 for the internal representation of dataclasses.
Works in 3.13.

Stacktrace:

Traceback (most recent call last):
  File "/xxx/.venv/bin/uadiscover", line 7, in <module>
    sys.exit(uadiscover())
             ~~~~~~~~~~^^
  File "/xxx/.venv/lib/python3.14/site-packages/asyncua/tools.py", line 684, in uadiscover
    asyncio.run(_uadiscover())
    ~~~~~~~~~~~^^^^^^^^^^^^^^^
  File "/usr/lib/python3.14/asyncio/runners.py", line 204, in run
    return runner.run(main)
           ~~~~~~~~~~^^^^^^
  File "/usr/lib/python3.14/asyncio/runners.py", line 127, in run
    return self._loop.run_until_complete(task)
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
  File "/usr/lib/python3.14/asyncio/base_events.py", line 719, in run_until_complete
    return future.result()
           ~~~~~~~~~~~~~^^
  File "/xxx/.venv/lib/python3.14/site-packages/asyncua/tools.py", line 720, in _uadiscover
    for i, server in enumerate(await client.connect_and_find_servers(), start=1):
                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/xxx/.venv/lib/python3.14/site-packages/asyncua/client/client.py", line 286, in connect_and_find_servers
    await self.open_secure_channel()  # spec says it should not be necessary to open channel
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/xxx/.venv/lib/python3.14/site-packages/asyncua/client/client.py", line 410, in open_secure_channel
    result = await self.uaclient.open_secure_channel(params)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/xxx/.venv/lib/python3.14/site-packages/asyncua/client/ua_client.py", line 344, in open_secure_channel
    return await self.protocol.open_secure_channel(params)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/xxx/.venv/lib/python3.14/site-packages/asyncua/client/ua_client.py", line 259, in open_secure_channel
    await wait_for(self._send_request(request, message_type=ua.MessageType.SecureOpen), self.timeout)
                   ~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/xxx/.venv/lib/python3.14/site-packages/asyncua/client/ua_client.py", line 153, in _send_request
    binreq = struct_to_binary(request)
  File "/xxx/.venv/lib/python3.14/site-packages/asyncua/ua/ua_binary.py", line 344, in struct_to_binary
    serializer = create_dataclass_serializer(obj.__class__)
  File "/xxx/.venv/lib/python3.14/site-packages/asyncua/ua/ua_binary.py", line 332, in create_dataclass_serializer
    encoding_functions = [(f.name, field_serializer(f.type, dataclazz)) for f in data_fields]
                                   ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^
  File "/xxx/.venv/lib/python3.14/site-packages/asyncua/ua/ua_binary.py", line 284, in field_serializer
    serializer = create_type_serializer(uatype)
  File "/xxx/.venv/lib/python3.14/site-packages/asyncua/ua/ua_binary.py", line 369, in create_type_serializer
    if issubclass(uatype, Enum):
       ~~~~~~~~~~^^^^^^^^^^^^^^
TypeError: issubclass() arg 1 must be a class

To Reproduce

Use uadiscover or the default example to connect to a server.

Version

Python-Version: 3.14.0

opcua-asyncio Version (e.g. master branch, 0.9): 1.1.8

[jpwelchie]

Same.

[schroeder-]

issubclass(uatype, Enum) must be change to isinstance(uatype, Enum)

[oroulet]

master passes all tests with 3.14 now https://github.com/FreeOpcUa/opcua-asyncio
Please test and report any issue. Changes are rather big

[Hytac]

master passes all tests with 3.14 now https://github.com/FreeOpcUa/opcua-asyncio Please test and report any issue. Changes are rather big

Does they run on windows? my test passes on linux docker but not windows.

[oroulet]

No ideas, I do not have any windows machine. MR wecome

[jamilraichouni]

Hi!

I can reproduce this on Fedora Linux and macOS for asyncua v1.1.8.

When the following script is executed with Python 3.14

import asyncio
import logging

import asyncua

logging.basicConfig(level="ERROR")
SERVER_URL = "opc.tcp://0.0.0.0:4840/"


async def main():
    server = asyncua.Server()
    await server.init()
    server.set_endpoint(SERVER_URL)
    server.set_security_policy([asyncua.ua.SecurityPolicyType.NoSecurity])
    await server.start()
    try:
        async with asyncua.Client(url=SERVER_URL):
            pass
    finally:
        await server.stop()


if __name__ == "__main__":
    asyncio.run(main(), debug=True)

Traceback:

Traceback (most recent call last):
  File "/mnt/volume/dev/dbgitlab/opc-ua-server/test_python_3_14.py", line 24, in <module>
    asyncio.run(main(), debug=True)
    ~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^
  File "/opt/python/cpython-3.14.0-linux-aarch64-gnu/lib/python3.14/asyncio/runners.py", line 204, in run
    return runner.run(main)
           ~~~~~~~~~~^^^^^^
  File "/opt/python/cpython-3.14.0-linux-aarch64-gnu/lib/python3.14/asyncio/runners.py", line 127, in run
    return self._loop.run_until_complete(task)
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
  File "/opt/python/cpython-3.14.0-linux-aarch64-gnu/lib/python3.14/asyncio/base_events.py", line 719, in run_until_complete
    return future.result()
           ~~~~~~~~~~~~~^^
  File "/mnt/volume/dev/dbgitlab/opc-ua-server/test_python_3_14.py", line 17, in main
    async with asyncua.Client(url=SERVER_URL):
               ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^
  File "/mnt/volume/dev/dbgitlab/opc-ua-server/.venv/lib/python3.14/site-packages/asyncua/client/client.py", line 97, in __aenter__
    await self.connect()
  File "/mnt/volume/dev/dbgitlab/opc-ua-server/.venv/lib/python3.14/site-packages/asyncua/client/client.py", line 320, in connect
    await self.open_secure_channel()
  File "/mnt/volume/dev/dbgitlab/opc-ua-server/.venv/lib/python3.14/site-packages/asyncua/client/client.py", line 410, in open_secure_channel
    result = await self.uaclient.open_secure_channel(params)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/mnt/volume/dev/dbgitlab/opc-ua-server/.venv/lib/python3.14/site-packages/asyncua/client/ua_client.py", line 344, in open_secure_channel
    return await self.protocol.open_secure_channel(params)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/mnt/volume/dev/dbgitlab/opc-ua-server/.venv/lib/python3.14/site-packages/asyncua/client/ua_client.py", line 259, in open_secure_channel
    await wait_for(self._send_request(request, message_type=ua.MessageType.SecureOpen), self.timeout)
                   ~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/mnt/volume/dev/dbgitlab/opc-ua-server/.venv/lib/python3.14/site-packages/asyncua/client/ua_client.py", line 153, in _send_request
    binreq = struct_to_binary(request)
  File "/mnt/volume/dev/dbgitlab/opc-ua-server/.venv/lib/python3.14/site-packages/asyncua/ua/ua_binary.py", line 344, in struct_to_binary
    serializer = create_dataclass_serializer(obj.__class__)
  File "/mnt/volume/dev/dbgitlab/opc-ua-server/.venv/lib/python3.14/site-packages/asyncua/ua/ua_binary.py", line 332, in create_dataclass_serializer
    encoding_functions = [(f.name, field_serializer(f.type, dataclazz)) for f in data_fields]
                                   ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^
  File "/mnt/volume/dev/dbgitlab/opc-ua-server/.venv/lib/python3.14/site-packages/asyncua/ua/ua_binary.py", line 284, in field_serializer
    serializer = create_type_serializer(uatype)
  File "/mnt/volume/dev/dbgitlab/opc-ua-server/.venv/lib/python3.14/site-packages/asyncua/ua/ua_binary.py", line 368, in create_type_serializer
    if issubclass(uatype, Enum):
       ~~~~~~~~~~^^^^^^^^^^^^^^
TypeError: issubclass() arg 1 must be a class

Looks like the tests do not pass this code route.

That Python 3.14 comes with syntax highlighting for the REPL (including pdb) is one of several reasons why it is interesting to make asyncua compatible with Python 3.14.

All best,
Jamil

[oroulet]

As written over. This is fixed in master. We need to release

[jamilraichouni]

Thank you! Misunderstood that. What is missing for a new release?

[oroulet]

Thank you! Misunderstood that. What is missing for a new release?

Testing. Do if you can test in your application against a real plc it will help

[jamilraichouni]

The test coverage is claimed to be at around 95%.
Instead of manual testing, the tests should be run in a matrix for the main operating systems using GitHub actions.

[oroulet]

The test coverage is claimed to be at around 95%.
Instead of manual testing the tests should be run in a matrix for the main operating systems using GitHub actions.

Useless but make a MR and I will consider.
Better would be running against a farm of different PLC. You are welcome to help

[jamilraichouni]

It can help and is quite common to run tests for different operating systems and also for different Python versions via GitHub actions in a matrix. I think I try to suggest something and create a PR. Need to check, when I find time next week.