Handle KernelWidgetManager in the JupyterLab OutputModel

[jtpio]

Investigating an issue in voila-dashboards/voila#846 where using an interactive_output would trigger the following error:

TypeError: Cannot read properties of undefined (reading 'sessionContext')

voila-dashboards/voila#846 uses the JupyterLab packages but with a custom KernelWidgetManager, not a WidgetManager like in the JupyterLab extension. This is because it only has access to a kernel connection, not a document context.

However in its present state, the OutputModel assumes it can access the context from its widget_manager here:

ipywidgets/python/jupyterlab_widgets/src/output.ts

Line 36 in 58adde2

this.widget_manager.context.sessionContext.kernelChanged.connect(

Ideally it should be able to handle both a WidgetManager and KernelWidgetManager or even a LabWidgetManager directly.

---

For reference the widget_manager assigned to a WidgetModel is declared as any here:

ipywidgets/packages/base/src/widget.ts

Line 72 in 58adde2

widget_manager: any;

And assigned here:

ipywidgets/packages/base/src/widget.ts

Line 124 in 58adde2

this.widget_manager = options.widget_manager;

[github-actions]

👈 Launch a binder notebook on branch jtpio/ipywidgets/output-model-kernel-widget-manager

[jtpio]

Unfortunately changing from a more specialized to a more generic type here looks like a breaking change.

[jtpio]

Thinking that another approach could be for those defining their own widget manager based on a KernelWidgetManager to also define their own OutputModel and register it.

Although this means duplicating quite a bit of code from ipywidgets and change the handling of the context / kernel.

[jtpio]

Thinking that another approach could be for those defining their own widget manager based on a KernelWidgetManager to also define their own OutputModel and register it

Linking to voila-dashboards/voila@3840999 which implements this approach (may be temporary).

[vidartf]

Unfortunately changing from a more specialized to a more generic type here looks like a breaking change.

Having breaking changes and therefore a major version bump on the lab manager isn't necessarily that problematic though.

[vidartf]

This looks good, but will probably require a major version bump of the jupyterlab extension (at least on the JS side), since the typing on the OutputModel changes. That should hopefully not be a big problem though.

[martinRenou]

Thanks!

[stevejpurves]

This looks like this could have been released in 8.0.x already but the milestone shows 8.1, i'n still seeing an error in 8.0.4 and wanted to check that this was expected?

[jtpio]

Since this change affects the jupyterlab-widgets Python package only, looks like it should have be available now? The latest release shows December 22, 2022 on PyPI:

[jtpio]

So a quick way to check could be to upgrade to the latest version with python -m pip install -U jupyterlab-widgets

[stevejpurves]

Thanks for the orientation @jtpio - i've just confirmed i'm running that version in jupyterlab and I can see the change in @jupyter-widgets/jupyterlab-manager 5.0.5 👍🏼