Add token on tree widget

[brichet]

Fixes #6410

The NotebookShell allows only one widget in the main area.
As the tree view is a TabPanel, it would be interesting to be able to add widgets (as it was possible in Classic Notebook).

This PR adds a token on the NotebookTreeWidget, the widget in main area in tree view.
Any extension will now be able to optionally try to retrieve the INotebookTree in the activate function, and add widgets in it using the TabPanel's interface functions.

It should close #6478 as a more generic implementation.

[github-actions]

👈 Launch a Binder on branch brichet/notebook/feature/tree_token

[jtpio]

Thanks @brichet for working on this.

Diff looks good. CI is currently broken because of ypy-websocket, pending a new pre-release of JupyterLab 4.0.

[brichet]

I called the widget and token NotebookTree, but I wonder if it should be something like NotebookMain or NotebookRoot to avoid confusion (for me, tree refers to tree files widget but I could be wrong).

[jtpio]

I called the widget and token NotebookTree

Right, this naming mostly comes from the name of the /tree endpoint.

Probably it's fine to keep that way for now while in alpha. We can always revisit later and maybe we could also rename the tree-extension as well.

[jtpio]

Looks like these two imports could be combined?

[jtpio]

Let's add a docstring to the class and constructor for consistency with the rest of the code base?

[jtpio]

The UI tests checks still appear to be cancelled after restarting them:

yarn run v1.22.17
$ playwright test --browser firefox

Running 24 tests using 1 worker
Error: The operation was canceled.

[brichet]

Thanks for reviewing @jtpio. I''l have a look at it.

[brichet]

A part of the tests are currently failing because of :

Failed to load toolbar items for factory FileBrowser from 
Error: Plugin `id` parameter is required for settings fetch.

So the tree widget toolbar is not displayed and filled with Upload and New buttons as expected.

[jtpio]

Any specific reason to move the activate function to a separate function?

Maybe we can keep inlined as part of the plugin definition for consistency with the rest of the code base?

[brichet]

Not really, I reverted it

[jtpio]

Thanks @brichet this is looking good.

I wanted to check on Binder but it seems like it doesn't start v7 anymore, which also happens on main:

Probably something changed in the setup (maybe the hatch migration), I'll have a look in a separate PR.

[jtpio]

Probably something changed in the setup (maybe the hatch migration), I'll have a look in a separate PR.

This should be fixed by #6505.

[brichet]

Probably something changed in the setup (maybe the hatch migration), I'll have a look in a separate PR.

This should be fixed by #6505.

Nice! But the binder link is created only when the PR opens the first time I think, so it will not work on this one.

[jtpio]

The binder link is created only when the PR opens the first time I think

Right but it doesn't change, so we can open it again or refresh the page.

[jtpio]

Thanks!