[v3.0.0rcx] Closing a chat session throws server error

[srdas]

This opens one of the issues in Issue #1293 as a separate issue.

References PR #1290

When closing a chat session (by clicking on the "x"), a websocket error is thrown, shown in the log below:

[I 2025-03-25 13:09:24.720 ServerApp] Saving the content from room text:chat:49f07d46-142c-4549-adee-b6c45d2c751e
[I 2025-03-25 13:09:24.722 YDocExtension] Saving file: sd3.chat
[E 2025-03-25 13:09:32.271 ServerApp] Failed to write message
    Traceback (most recent call last):
      File "/opt/anaconda3/envs/v3/lib/python3.12/site-packages/jupyter_server_ydoc/handlers.py", line 278, in send
        self.write_message(message, binary=True)
      File "/opt/anaconda3/envs/v3/lib/python3.12/site-packages/tornado/websocket.py", line 332, in write_message
        raise WebSocketClosedError()
    tornado.websocket.WebSocketClosedError

To reproduce from scratch:

1. Do a dev install of v3 as a contributor using the documentation here.
2. Start Jupyter Lab from the Terminal.
3. Open a new chat window (use the +Chat button)
4. Try some queries and chat in the chat window.
5. Close the chat window by clicking the "x" in the top bar.
6. Examine the log in the Terminal to see the error above.

Note: (a) The chat file <*.chat> is being saved correctly. (b) Error persists after upgrading tornado, jupyterlab, notebook.

[brichet]

Thanks @srdas for tracking this issue.

This issue is related to collaborative document, not only chat. See jupyterlab/jupyter-collaboration#455, and WIP at jupyterlab/jupyter-collaboration#456

Also referenced in jupyter-chat jupyterlab/jupyter-chat#113

[dlqqq]

Since this is invisible to most users, I'm moving this to the RC milestone to indicate this as a "minor bug to fix right before v3.0.0." 👍

[brichet]

This should be fixed, after y-crdt/pycrdt#256 and y-crdt/pycrdt-websocket#118, with an updated version of pycrdt-websocket (v0.15.5)