Introduce _typeshed.Maybe

[srittau]

We use the X | Any pattern for return types more and more. Introducing a type alias legitimizes the pattern, makes it easier to recognize, easier to grep, and means that we don't need to repeat the documentation.

[Akuli]

I like getting rid of the comment copy/pasta.

I'm not sure if Maybe is a good name for this, since it means "could be None and you must check for it" in some other languages, but I don't have better suggestions in mind.

[srittau]

I'm not sure if Maybe is a good name for this, since it means "could be None and you must check for it" in some other languages, but I don't have better suggestions in mind.

True, but it's succinct and has the meaning "could be unset/null/none/undefined" in other languages, so the name at least has some meaning, even if it's not a 100% match to what other languages do.

[hauntsaninja]

We've talked about WeakUnion before, so WeakOptional seems a pretty natural name to me

[github-actions]

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

[srittau]

I don't think we should use "optional". That name has caused lots of confusion in the past. Also, it's a fairly long name.

[Akuli]

RarelyNone?

[JelleZijlstra]

Probably? re.match probably returns a match, so it returns Probably[Match[str]].

[srittau]

We could bikeshed this forever, but I still think Maybe is the best option.

[AlexWaygood]

We could bikeshed this forever

Indeed we could, but I do think the choice of name is important here -- I'd prefer the status quo over a confusing alias name. Personally, I prefer either Probably or RarelyNone to Maybe 🙂

[srittau]

Probably and RarelyNone suggest that None is somehow the less common case. That's not true in many cases, for example Match.group() with optional groups.

[AlexWaygood]

Often? That has less of an implication that the result is necessarily the majority of cases, compared to Probably or RarelyNone.

[Akuli]

I think the name shouldn't be too clever or short. If you see Often in the middle of some code, how are you supposed to know that it has something to do with unions and None, let alone guess its meaning?

Maybe we should just call this TheAnyTrick. It's very obvious for typeshed maintainers. It isn't obvious at first for people new to typing, but this is a difficult concept, and I don't think we can make it guessable anyway.

[AlexWaygood]

Maybe we should just call this TheAnyTrick. It's very obvious for typeshed maintainers. It isn't obvious at first for people new to typing, but this is a difficult concept, and I don't think we can make it guessable anyway.

I'd be fine with AnyTrick or TheAnyTrick. I agree it's better to have an opaque name than a name that's too clever or succinct.

[srittau]

No consensus.