API change between Jupyter Lab v4 and v3 for retrieving an IKernelConnection

[jourdain]

Hi All,

I successfully got my extension working with JupyterLab v4, but now I'm struggling to port it back to v3 since it is still the version deployed in the cloud.

My extension specifically does 2 things with the IKernelConnection.

1. Execute some python code on the kernel itself (set env variables)
2. Create a comm to exchange messages using the existing network infrastructure.

But with the v3, I can't figure out how to get my hand on an IKernelConnection instance. In other words, my (app as JupyterFrontEnd).serviceManager.kernels is missing .kernels.

It would be great to have a simple example that automatically executes some code on any kernel that gets created and showcase how sessions and kernel instances should be managed.

Thanks for any pointers or help,

Seb

[jourdain]

Such an example could be great for highlighting how to properly handle the various life cycles of sessions and kernels.

[jourdain]

Actually, I figured out a path here but it would be great to have a reference implementation.

[jourdain]

Hum, it seems that my extension is pretty bad as it prevent any ipywidgets to work with some js error with a display "Error displaying widget: model not found"

jlab_core.c3f88431949a8243d08c.js?v=c3f88431949a8243d08c:2 Language pack 'en_US' not installed!
fetch @ jlab_core.c3f88431949a8243d08c.js?v=c3f88431949a8243d08c:2
523.6e13edd0a9dd3788d5ec.js:1 Error: widget model not found
    at x.get_model (523.6e13edd0a9dd3788d5ec.js:1:6291)
    at u.renderModel (523.6e13edd0a9dd3788d5ec.js:1:971)
renderModel @ 523.6e13edd0a9dd3788d5ec.js:1
523.6e13edd0a9dd3788d5ec.js:1 Error: widget model not found
    at x.get_model (523.6e13edd0a9dd3788d5ec.js:1:6291)
    at u.renderModel (523.6e13edd0a9dd3788d5ec.js:1:971)
renderModel @ 523.6e13edd0a9dd3788d5ec.js:1
523.6e13edd0a9dd3788d5ec.js:1 Error: widget model not found
    at x.get_model (523.6e13edd0a9dd3788d5ec.js:1:6291)
    at u.renderModel (523.6e13edd0a9dd3788d5ec.js:1:971)
renderModel @ 523.6e13edd0a9dd3788d5ec.js:1
523.6e13edd0a9dd3788d5ec.js:1 Error: widget model not found
    at x.get_model (523.6e13edd0a9dd3788d5ec.js:1:6291)
    at u.renderModel (523.6e13edd0a9dd3788d5ec.js:1:971)
renderModel @ 523.6e13edd0a9dd3788d5ec.js:1
jlab_core.c3f88431949a8243d08c.js?v=c3f88431949a8243d08c:2 Exception opening new comm
_handleCommOpen @ jlab_core.c3f88431949a8243d08c.js?v=c3f88431949a8243d08c:2
jlab_core.c3f88431949a8243d08c.js?v=c3f88431949a8243d08c:2 Exception opening new comm
_handleCommOpen @ jlab_core.c3f88431949a8243d08c.js?v=c3f88431949a8243d08c:2
523.6e13edd0a9dd3788d5ec.js:1 Error: widget model not found
    at x.get_model (523.6e13edd0a9dd3788d5ec.js:1:6291)
    at u.renderModel (523.6e13edd0a9dd3788d5ec.js:1:971)
renderModel @ 523.6e13edd0a9dd3788d5ec.js:1
jlab_core.c3f88431949a8243d08c.js?v=c3f88431949a8243d08c:2 Exception opening new comm
_handleCommOpen @ jlab_core.c3f88431949a8243d08c.js?v=c3f88431949a8243d08c:2

Any pointer on what I am missing or should do to improve my code would be great.

Thanks,

Seb

[jourdain]

For reference, some side conversation are happening here