ensure_native_kernel is ignored?

[dhirschfeld]

Description

Passing --KernelSpecManager.ensure_native_kernel=False to jupyter lab has no effect and the native kernel is still shown in the UI.

Reproduce

jupyter lab --no-browser --ip 0.0.0.0 --KernelSpecManager.ensure_native_kernel=False 

Go to JupyterLab and observe the native kernel is still in the UI

Expected behavior

The native kernel isn't shown in the JupyterLab UI

Context

• Ubuntu 22.04
• Chrome 129.0.6668.100
• Python 3.10.15

❯ pixi list | rg jupyter
jupyter-lsp                       2.2.5
jupyter_ai                        2.25.0
jupyter_ai_magics                 2.25.0
jupyter_app_launcher              0.3.0
jupyter_client                    8.6.3
jupyter_core                      5.7.2
jupyter_events                    0.10.0
jupyter_leaflet                   0.19.2
jupyter_server                    2.14.2
jupyter_server_proxy              4.4.0
jupyter_server_terminals          0.5.3
jupyterlab                        4.2.5
jupyterlab_deck                   0.2.0
jupyterlab_execute_time           3.2.0
jupyterlab_fonts                  3.0.0
jupyterlab_gist_it                0.2.1
jupyterlab_iframe                 0.5.0
jupyterlab_kernelspy              4.0.0
jupyterlab_lsp                    5.1.0
jupyterlab_miami_nights           0.4.2
jupyterlab_pygments               0.3.0
jupyterlab_rise                   0.42.0
jupyterlab_server                 2.27.3
jupyterlab_widgets                3.0.13
vegafusion_jupyter                1.6.9

[dhirschfeld]

In a paroxysm of rage I nuked the default kernel:

❯ jupyter kernelspec list
Available kernels:
  python3    /opt/python/envs/dev310/.pixi/envs/default/share/jupyter/kernels/python3
  dev310     ~/.local/share/jupyter/kernels/dev310
  dev312     ~/.local/share/jupyter/kernels/dev312

❯ rm -rf /opt/python/envs/dev310/.pixi/envs/default/share/jupyter/kernels/python3/

..but upon starting JupyterLab the default kernel was still there! 😡

Checking the available kernels again now showed:

❯ jupyter kernelspec list
Available kernels:
  python3    /opt/python/envs/dev310/.pixi/envs/default/lib/python3.10/site-packages/ipykernel/resources
  dev310     ~/.local/share/jupyter/kernels/dev310
  dev312     ~/.local/share/jupyter/kernels/dev312

So the ipykernel had appeared in place of the share/jupyter/kernels/python3 kernel.

Now however, --KernelSpecManager.ensure_native_kernel=False worked to correctly hide the default (ipykernel) kernel! 🎉

[dhirschfeld]

...so it seems something is installing a kernel in share/jupyter/kernels/python3/ which masks the default (ipykernel) kernel and which ignores the command line flag --KernelSpecManager.ensure_native_kernel=False.