Add stubs for WebTest

[Daverball]

A small testing framework for WSGI applications based around WebOb.

Source: https://github.com/Pylons/webtest/blob/3.0.6/webtest/__init__.py
Docs: https://docs.pylonsproject.org/projects/webtest/en/latest/

webtest.forms.Form turned out a little more lax than I would've liked. But making it more strict would've probably caused quite a bit of churn in test code, like not being able to use Checkbox.checked without first doing an isinstance check, or either having to do the same for Select.select/MultipleSelect.select_multiple or having to switch to Form.select/Form.select_multiple.

I also debated for a while on whether or not to make TestApp generic, but ultimately it seemed worth it, since if you have a test fixture that returns a TestApp, you don't necessarily want to have to specify another fixture in order to get at the WSGIApplication that's being tested with the correct type information. Giving the TypeVar a default of WSGIApplication should end up making it behave more or less the same as the non-generic version, if you don't care about being able to access the application through TestApp.app.

[donBarbos]

Thanks for contributing! I couldn't find any prior discussion about adding type hints directly to the package, but it does seem like preferred option, so I think it's worth opening an issue to suggest this idea to WebTest maintainers.
(If you've seen such a discussion, you can attach link in your PR message as one of the reasons for adding stubs to typeshed)

[Daverball]

Thanks for contributing! I couldn't find any prior discussion about adding type hints directly to the package, but it does seem like preferred option, so I think it's worth opening an issue to suggest this idea to WebTest maintainers. (If you've seen such a discussion, you can attach link in your PR message as one of the reasons for adding stubs to typeshed)

Considering my PR to add my WebOb stubs as inline type hints to WebOb has been open for half a year without so much as a peep from a maintainer and them both being Pylons projects I decided not to bother spending the extra amount of time required to add inline hints, and I needed the stubs for something I was working on anyways, so it was quicker to just get it done. So since I already had them I decided to just contribute them.

That being said, WebTest does have a different maintainer, which appears to be ever so slightly more active, so I'm willing to try: Pylons/webtest#271

[srittau]

Considering that there has been no response upstream, it makes sense to me to add this typeshed.

[srittau]

Considering that Sequence is not a protocol, using a real protocol (from collections.abc or _typeshed) would be better.

[Daverball]

I considered using Collection, the minimum requirement appears to be Iterable & Sized at first glance, but since the docs and error message say list I wanted to be a little more conservative, in case some implementation details change, without making it annoying to pass in lists that contain a type that's compatible with tuple[str, str] | tuple[str, str, bytes].

[srittau]

See above. More instances below.

[Daverball]

This matches what beautifulsoup4 expects for the features parameter, so I think it should stay like this.

[srittau]

Same is true for Mapping (with more instances below).

[Daverball]

Actually I just noticed Mapping is too broad for extra_environ, since the implementation does del extra_environ[key]. I probably should just change this to _typeshed.wsgi.WSGIEnvironment, like I initially had planned to, the documentation explicitly says dict as well.

For params I probably should use _QueryType from urllib.parse.

headers is another one that is too narrow currently, if xhr=True it needs to be able to be able support update called with a dict, so at best we could reduce that SupportsItems & SupportsUpdate, but I'm not sure whether it's worth the extra effort, it might be easier to just switch to the documented dict or MutableMapping.

[Daverball]

I take it back params needs to be different because of utils.encode_params which does isinstance(params, (list, tuple)) and also does list(params.items() if params has items. So it needs to be some complex combination of SupportsItems list and tuple.

encode_multipart which is used if there are any file uploads, has slightly different requirements once again which poses some hard restrictions on what the value type can be, which isn't great for list, so I might opt for using Sequence after all.

[Daverball]

And it looks like extra_environ only needs to be dict in the constructor after all, everywhere else everything that works with dict.update(extra_environ) is fine, as long as it is also Sized.

[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

discord.py (https://github.com/Rapptz/discord.py)
- discord/ext/commands/hybrid.py:508: error: Overlap between argument names and ** TypedDict items: "name", "description"  [misc]
+ discord/ext/commands/hybrid.py:508: error: Overlap between argument names and ** TypedDict items: "description", "name"  [misc]
- discord/ext/commands/hybrid.py:629: error: Overlap between argument names and ** TypedDict items: "name", "description"  [misc]
+ discord/ext/commands/hybrid.py:629: error: Overlap between argument names and ** TypedDict items: "description", "name"  [misc]
- discord/ext/commands/hybrid.py:834: error: Overlap between argument names and ** TypedDict items: "name", "with_app_command"  [misc]
+ discord/ext/commands/hybrid.py:834: error: Overlap between argument names and ** TypedDict items: "with_app_command", "name"  [misc]
- discord/ext/commands/hybrid.py:858: error: Overlap between argument names and ** TypedDict items: "name", "with_app_command"  [misc]
+ discord/ext/commands/hybrid.py:858: error: Overlap between argument names and ** TypedDict items: "with_app_command", "name"  [misc]
- discord/ext/commands/hybrid.py:883: error: Overlap between argument names and ** TypedDict items: "name", "with_app_command"  [misc]
+ discord/ext/commands/hybrid.py:883: error: Overlap between argument names and ** TypedDict items: "with_app_command", "name"  [misc]
- discord/ext/commands/hybrid.py:935: error: Overlap between argument names and ** TypedDict items: "name", "with_app_command"  [misc]
+ discord/ext/commands/hybrid.py:935: error: Overlap between argument names and ** TypedDict items: "with_app_command", "name"  [misc]
- discord/ext/commands/bot.py:290: error: Overlap between argument names and ** TypedDict items: "name", "with_app_command"  [misc]
+ discord/ext/commands/bot.py:290: error: Overlap between argument names and ** TypedDict items: "with_app_command", "name"  [misc]
- discord/ext/commands/bot.py:314: error: Overlap between argument names and ** TypedDict items: "name", "with_app_command"  [misc]
+ discord/ext/commands/bot.py:314: error: Overlap between argument names and ** TypedDict items: "with_app_command", "name"  [misc]