python comm crashes XPython kernel

[albop]

Here is how to reproduce it:

• Setup the environment

pixi init
pixi add xeus-python jupyterlab
pixi run jupyter lab

• Then create a jupyter notebook using kernel XPython
• Run a single cell with content:

from comm import Comm
comm = Comm(target_name="test2")

The result is a kernel crash. I'm on linux.

[martinRenou]

I recall this was fixed in upstream xeus as part of the comms refactor. But these changes are not used by xeus-python yet

If I'm correct, this is the byproduct of missing the comm target registering. As in, before you can create a comm with this target, you need register the target.

import comm

def handle_comm_opened(*args, **kwargs):
    # TODO handle comm open from front-end
    pass


comm_manager = comm.get_comm_manager()
if comm_manager is not None:
    comm_manager.register_target("test2", handle_comm_opened)

[JohanMabille]

You mean it is fixed in this PR ?

[martinRenou]

That's what I recall from past discussion we had, though I may be wrong.

The problem is when we try to create a comm with a non-registered target, it crashes instead of failing with a nice error message.

[JohanMabille]

I've just tested, it fixes the problem.