Add missing __reduce__ and __reduce_ex__ methods to datetime classes

[AlexWaygood]

No description provided.

[github-actions]

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

[JelleZijlstra]

This has a merge conflict now.

I'm not terribly enthusiastic about adding __reduce__ methods, and especially their precise return types, because those are implementation details that people generally shouldn't rely on. Did you have a specific use case for this PR? We do have a few dozen __reduce__ method definitions in typeshed already.

[AlexWaygood]

I'm not terribly enthusiastic about adding __reduce__ methods, and especially their precise return types, because those are implementation details that people generally shouldn't rely on. Did you have a specific use case for this PR? We do have a few dozen __reduce__ method definitions in typeshed already.

No specific use case — happy to close it if you think it's more trouble than it's worth. Was simply comparing the stub with the output from help(), and noticed the missing methods. I'll confess I don't really know much about these methods.

Your point about the precise return type being an implementation detail is a good one — happy to make the return types more vague. I think including the methods in some form might be useful to a user of the stubs, however, given that quite a few objects aren't pickleable. The user would see these methods (with a non-NoReturn return type), and know that these objects are pickleable. But on the other hand, maybe the user should just go to the documentation to find out that piece of information.

Anyway, happy to either revise this or close this.