Widgets not rendering after reloading vscode

[Syndorik]

Environment data

• VS Code Insiders: 1.56.0-insider 550035808407c15252e581e8abe1b820b9d311ee x64
• Jupyter Extension version (available under the Extensions sidebar): 2021.6.718745073
• Python Extension version (available under the Extensions sidebar): 2021.3.680753044
• OS (Windows | Mac | Linux distro) and version: Windows10
• Python and/or Anaconda version: 3.9.2
• Type of virtual environment used (N/A | venv | virtualenv | conda | ...): conda
• Jupyter server running: Remote
• IpyWidgets==7.6.3

Behavior

When I'm initializing the jupyter server, connecting the notebook for the first time and runing the following cell

from tqdm.notebook import tqdm
[k for k in tqdm(range(10))]

The ipywidget is displaying correctly. However, if I exit the notebook and comeback or if I reload the notebook, the Ipywidget does not render anymore.

When I toggle the developper tools, on reload I have the following warning

[rchiodo]

This is a side effect of us closing kernels when closing notebooks. Jupyter has the same problem but at least tells you why:

[Syndorik]

Ok thanks for the information,
But, when I rerun the cell with a new runing kernel, the widget is still not rendering. In jupyter I think the ipywidgets is rerendering if you rerun the cell with a new kernel after shuting down the other.
In vscode if I close a notebook/reload it and then rerun the cell it doesn't work.

[rchiodo]

I'm reproing that too. Very weird. Although closing and reopening the notebook makes it work for me.

My guess is that reloading a kernel does not remove the preload scripts that the first kernel added. This interferes with ipywidgets working.

[Syndorik]

I tested, and I need to kill all runing kernel (via the rest API) and then reload the window. If I do that, the IpyWidgets works again. Just closing the notebook an reopening it doesn't work for me

[rchiodo]

If VS code provides a way to detect this we should use it, or we need to set some global state to detect this ourselves.

[DonJayamanne]

In general IPyWidgets will not be re-loaded whether we re-load or close/re-open a notebook, unless we have #4404 (which is what Rich has highlighted #5424 (comment))

[joyceerhl]

Validated (I think). In Insiders now if I execute a notebook with ipyvolume widgets, then reload, the widget doesn't initially show, but I can reexecute the cell and see the widget appear in the cell output.