Replace TypeAlias _ClassLevelWidgetT with descriptor _WidgetTypeOrInstance

[michalpokusa]

I have made things!

Related issues

None I could find.

This change allows for recognizing when .widget is used on Field instance and when on the type itself, allowing for different type annotations in each case.

Why even bother?
Example: Currently this correct code does not recognize is_required and attrs on field.widget, because it might be a type and not an instance.

After the change all types are correctly inferred, and syntax highlighting works as expected:

I hope you find it worth adding.

[sobolevn]

Looks like a good idea! Thanks!

Please, fix the CI :)

[michalpokusa]

@sobolevn I think I might need some help there. I checked why the CI is failing and it looks like errors are not even slightly related to what I have changed.

I checkouted the current origin/HEAD, ran the test locally and also I got a lot of errors. Is there something obvious I am missing? I believe there might be a problem with the CI itself as I see that on other PR #2616 also fails in the same way.

[UnknownPlatypus]

Setuptools version 79 got installed, I suppose it probably breaks the multiple SETUPTOOLS_ENABLE_FEATURES in ci

[sobolevn]

you can pin older setuptools for now in a separate PR :)

[sobolevn]

Can you please also add several type assertions for this? https://github.com/typeddjango/django-stubs/tree/master/tests/assert_type

[michalpokusa]

@sobolevn I started adding type assertions, and I would like to get you point of view on one thing. I could leave this as typing everything as the most general Widget, or I could make it generic, and type widget individually for each field type.

Example:

It provides more precise typing, but I am not sure whether it is not too restrictive.
On the other hand MultipleChoiceField could have a widget of type SelectMultiple or CheckboxSelectMultiple.
And how should it work with custom field types and custom widgets, wouldn't it break them?

What do you think about that?

[sobolevn]

Let's first add the simplest typing possible. We can later update it to cover more cases.

[michalpokusa]

I have added assert type tests.

Seems like this is a bit more complex than I initailly assumed, right now there is a problem with stubtest.
All the errors center around widgets being MediaDefiningClass instances. The interesting thing is that e.g. Field.hidden_widget is typed as type[Widget], while BaseFormSet.deletion_widget as MediaDefiningClass inside ".pyi" files.

Any further guidance would be highly appreciated.

[sobolevn]

Based on the amount of failures I would say that this seems overly complex to type properly :(

However, I am open to ideas.