Add a scratch-pad console to the notebook

[brichet]

This PR allows to open a console next to a Notebook (scratch-pad like), sharing the same kernel.

there are several way to open it from a Notebook view:

• from the menu menu>new>Scratch-pad console
• from the commands palette
• from the shortcut Ctrl + B

Fixes #7707

Remaining tasks:

• allow the console commands to run in the side panel (Fix console commands enabled status if not in main area jupyterlab/jupyterlab#18238)
• do not toggle the side panel after the command is executed (related to activateById toggle side panel instead of expanding it #7534)
• add tests

[github-actions]

👈 Launch a Binder on branch brichet/notebook/scratchpad-console

[brichet]

EDIT: this comment is now solved, the PR has been rebased with #7799

do not toggle the side panel after the command is executed

When the command is executed, it seems that a activateById is called on the shell. In Notebook, this commands hide the side panel if it is already display (see #7534 for more context).

We can see in the screen recording below that the command is executed, though, but the console needs to be reopened.

record-2025-12-18_16.03.53.webm

[brichet]

This extension is not enabled anymore, except for the tree view, because it already uses the Ctrl + B shortcut.
AFAIK the commands in this extension may not be necessary for the Notebook view (not sure it is necessary at all, most of them requires a LabShell to work).

[brichet]

Reopening it, it has been closed by error by the description of #7799

[jtpio]

Thanks for working on this!

Wondering if we could use a more descriptive title in the menu entry when the scratchpad is open:

Also when testing locally there seems to be an issue about not being able to change the prompt position when the scratchpad is open:

notebook-scratchpad-console.mp4

[brichet]

Thanks @jtpio for the review, I updated the PR according to your comments.

Wondering if we could use a more descriptive title in the menu entry when the scratchpad is open:

The menu entry uses the widget title, and the one from console is updated when a property or kernel changes. If we use the same signal in Notebook, it will conflict and we can't know which one will be triggered first. An option could be to add an flag in the constructor of the console (in Jupyterlab), to disable the title update.

Also when testing locally there seems to be an issue about not being able to change the prompt position when the scratchpad is open

In jupyterlab/jupyterlab#18238, we added a way to enable the commands when the console is not in main area, but missed this use case. It uses the fact that the current console contains the activeElement. The menu to change the prompt position is attached to the root of the DOM, not to the node of the console. We should fix it upstream too (or make some kind of patch in Notebook, but I don't think we should go with this solution).

[brichet]

The menu entry uses the widget title, and the one from console is updated when a property or kernel changes. If we use the same signal in Notebook, it will conflict and we can't know which one will be triggered first. An option could be to add an flag in the constructor of the console (in Jupyterlab), to disable the title update.

I opened jupyterlab/jupyterlab#18331 to fix it.

In jupyterlab/jupyterlab#18238, we added a way to enable the commands when the console is not in main area, but missed this use case. It uses the fact that the current console contains the activeElement. The menu to change the prompt position is attached to the root of the DOM, not to the node of the console. We should fix it upstream too (or make some kind of patch in Notebook, but I don't think we should go with this solution).

I opened jupyterlab/jupyterlab#18332 to fix it.

@jtpio do you think that we should wait for these PR to be merged and release before ? If so, we should set this PR as draft for now.

[jtpio]

Ah thanks for opening the PRs upstream!

Yeah it's ok if this gets fixed later. We can track that in an issue and fix it when updating to the next JupyterLab 4.6.0a2.

[jtpio]

Thanks!