make BaseModelAdmin generic to properly type methods dealing with models

[ghost]

i have made things!

related issues

closes #482

this is my first time really working with mypy like this, apologies if i made any mistakes that i didn't catch

[ghost]

black failed in ci, but when i ran it locally it wanted to make a lot of completely unrelated changes, which i figured wouldn't really be good for this pr

[sobolevn]

Thanks! 👍

Please, reformat this file only, I think that it is ok to trust black to do its job.
Maybe it has a new version / rule to apply.

[ghost]

i added a new typevar _ModelT that's bound to Model, and if an argument to a method looked like it should be generic, i typed it as _ModelT. i wasn't super sure on some of them, but i figured it would be better to be safe, since i don't think it'll really create any issues

[sobolevn]

Awesome work! 👍

Let's add a single test case for ModelAdmin class! Currently, we are terrible at test-coverage 😞
You can take some inspiration from https://github.com/typeddjango/django-stubs/blob/master/test-data/typecheck/contrib/admin/test_options.yml

[ghost]

i'd love to add a test case, but i'm not quite clear on what i would test. just write subclass of ModelAdmin to make sure it typechecks?

[sobolevn]

I was thinking about revealing type of https://github.com/typeddjango/django-stubs/pull/504/files#diff-8143d231653e2933a801943d02bd50968776e6f1805a191aad7012d4881b129cR162

[ghost]

would something like this work? reveal_type worked, but the output looked really unintuitive, so i figured it might be best to just have the field typecheck

if that's good with you, i'll add something that doesn't typecheck to make sure the constraint works properly

[sobolevn]

Thanks a lot!

[sobolevn]

if that's good with you, i'll add something that doesn't typecheck to make sure the constraint works properly

Feel free to send a new PR with an extra test 👍