Support user_expressions in kernel execute requests

[juntyr]

Fixes #251

[github-actions]

👈 Try it on ReadTheDocs

[juntyr]

Thanks for taking a look @jtpio! What's the current (rough) timeline for v0.8.0?

[jtpio]

Thanks @juntyr!

Just tried locally with the built wheel for this PR and jupyterlab-myst. It seems like it requires the markdown cell to be run twice for the expression to be evaluated and rendered correctly?

jupyterlite-pyodide-kernel-user-expressions.mp4

[juntyr]

@jtpio Huh. I developed this by putting breakpoints into the relevant myst and kernel code, and with that, everything worked correctly, updating immediately. So I wonder if me using breakpoints messed with some timings to allow the updates to go through the first time.

What does your dev console say when you first execute the cell? Mine is always full of myst debug logs

[jtpio]

Actually this may be a more general issue with JupyterLab or jupyterlab-myst, as this also happens with jupyterlab==4.5.3 and jupyterlab-myst==2.6.0:

jupyterlab-myst-eval.mp4

[juntyr]

@jtpio That could be it! I was testing with jupyterlab~=4.5.0 (likely 4.5.2 when I created this PR) and jupyterlab-myst~=2.6.0 (2.6.0)

[juntyr]

@jtpio Is there anything still needed for this PR?

[jtpio]

The PR itself looks good.

The remaining question was more to know where the issue mentioned above belongs. I see you opened jupyter-book/jupyterlab-myst#289 so maybe we can just move forward with this and keep an eye on jupyter-book/jupyterlab-myst#289.