Recreate nbgrader widgets after they are disposed.

[ykazakov]

Fixes #1772

I did not add tests to reproduce the issue. This would require a bit more work.

[github-actions]

👈 Launch a Binder on branch ykazakov/nbgrader/master

[brichet]

Thanks @ykazakov
This also fixes #1722

It would be great if you could add some tests.
I can give some hints if needed.

[ykazakov]

It would be great if you could add some tests. I can give some hints if needed.

I can give it a try.
I found relevant functions to open the menus, e.g:

nbgrader/nbgrader/tests/labextension_ui-tests/tests/test_assignment_list.spec.ts

Line 92 in 05bb458

const open_assignment_list = async (page:IJupyterLabPageFixture) => {

Any idea how to close the opened tab?

[brichet]

This is the correct function.
It may be added to the following test (for assignment list) or a new test can be created.

nbgrader/nbgrader/tests/labextension_ui-tests/tests/test_assignment_list.spec.ts

Line 155 in 05bb458

test('Open assignment list tab from menu', async({

I think the close icon have the class lm-TabBar-tabCloseIcon, so maybe we could simulate a click on it (be sure to select the correct one if several tabs are opened or if there is another TabBar).

[tuncbkose]

By the way, I submitted an identical pull request two weeks ago (#1756).

[ykazakov]

I have now extended the UI tests upon suggestion of @brichet (with a little of refactoring). The tests fail without the patch.

@tuncbkose sorry I did not notice the identical issue #1722. I noticed that the bug is still present in the latest release 0.8.2, so I did not check for old issues. :-/

[brichet]

Thanks @ykazakov