make ExitStack/AsyncExitStack not appear as abstract

[KotlinIsland]

in basedpyright/pycharm the explicit usage of ABCMeta/ABC causes the class to be treated as abstract and report an error. these classes are defined a little different to reality, so they had ABCMeta, i've just moved that to the base class to resolve the problems it was causing

[AlexWaygood]

in basedpyright/pycharm the explicit usage of ABCMeta/ABC causes the class to be treated as abstract and report an error

Hmm, isn't that a bug in those tools? These classes don't have any abstract methods on them. Having ABCMeta as the metaclass isn't sufficient to make a class abstract. Lots of classes have that metaclass but can still be soundly instantiated at runtime

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉

[KotlinIsland]

Hmm, isn't that a bug in those tools? These classes don't have any abstract methods on them. Having ABCMeta as the metaclass isn't sufficient to make a class abstract. Lots of classes have that metaclass but can still be soundly instantiated at runtime

no, it's intended behaviour, most languages with abstract classes work like that: https://play.kotlinlang.org/#eyJ2ZXJzaW9uIjoiMi4zLjEwIiwicGxhdGZvcm0iOiJqYXZhIiwiYXJncyI6IiIsIm5vbmVNYXJrZXJzIjp0cnVlLCJ0aGVtZSI6ImlkZWEiLCJjb2RlIjoiYWJzdHJhY3QgY2xhc3MgQVxuXG5mdW4gbWFpbigpIHtcbiAgICBBKClcbn0ifQ==

so the author of the class can indicate: "you shouldn't instantiate this class directly, it's abstract. you should subtype it"

[AlexWaygood]

no, it's intended behaviour, most languages with abstract classes work like that

that's certainly interesting, but it's not how Python works at runtime and I think type checkers should follow the runtime here. No other type checker has this behaviour -- here's a gist you can load into multiplay: 4abd6426cf1b97d8453e1822236246f9.

[KotlinIsland]

but it's not how Python works at runtime and I think type checkers should follow the runtime here.

at runtime python doesn't care about type annotations, so to say that we should always be relaxed as the runtime permits isn't valid to me. i think this is a matter of opinion, i think it is a very valuable addition to the type checker that i have taken advantage of in my work, and the need for it was what motivated me and others to implement it to begin with

of course i wouldn't want to corrupt typeshed to appease some bizarre non-standard feature, but for this specific case, it is a simple fix that actually reduces the duplication of the implementation, while also helping to remove some false positives from these tools