Reduce code duplication in the email module

[AlexWaygood]

2 type aliases and one TypeVar have duplicate definitions in several email submodules. I think it makes sense to move these definitions to a submodule in _typeshed instead, to reduce code duplicaiton.

[srittau]

Sorry for the late reply, but do we need this in _typeshed? Wouldn't it make more sense to have those aliases in one of the email modules and import from there?

[AlexWaygood]

Sorry for the late reply

No worries — no rush!

but do we need this in _typeshed? Wouldn't it make more sense to have those aliases in one of the email modules and import from there?

Sure — though if we do that, we'll probably have to give them names with a leading underscore, and it feels a bit weird to import names with a leading underscore from other modules.

I also thought that we already did something similar with _typeshed.xml and _typeshed.wsgi — but perhaps I just misunderstood the purpose of those submodules :)

[srittau]

At least the aliases and protocols in .wsgi are mainly intended for external use, while the aliases here are more for internal use, if I understand correctly?

[AlexWaygood]

the aliases here are more for internal use, if I understand correctly?

Yes.

[srittau]

To me, _typeshed is mainly intended for types that are also useful for typeshed users, or at least for types that are used by multiple parts of typeshed, while module-specific types should stay close to where they are used. But I'd be interested in what the general opinion on that is.

[AlexWaygood]

What do we think about perhaps adding a fictitious submodule to the email package (_aliases.pyi? _typing.pyi?) that, like _typeshed, doesn't exist at runtime?

[AlexWaygood]

What do we think about perhaps adding a fictitious submodule to the email package (_aliases.pyi? _typing.pyi?) that, like _typeshed, doesn't exist at runtime?

There appears to be little enthusiasm for this idea. I'll move the aliases to email.__init__ :)

[github-actions]

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

[AlexWaygood]

Thanks @srittau!

[srittau]

What do we think about perhaps adding a fictitious submodule to the email package (_aliases.pyi? _typing.pyi?) that, like _typeshed, doesn't exist at runtime?

Sorry for not answering earlier: _typeshed.wsgi used to be wsgiref._types, so there is precedent for that. But I prefer not to have "fake" modules, although I don't have a good justification for that, it's just a gut feeling.