with hmpp can i define an expect class in commonMa...

# multiplatform

[jw]

with hmpp can i define an expect class in commonMain, redefine it as an expect in intermediateMain with more functions, and then actual it in platformMain?

[russhwolf]

I’ve never tried, but you might be able to hack it with a typealias

commonMain

expect class Foo { ... }

intermediateMain

actual typealias Foo = Bar
expect class Bar { ... }

platformMain

actual class Bar { ... }

[jw]

ahaha oh my god this is horrible

[jw]

if somehow i could hide Bar from public API I would love it

[Sebastian Sellmair [JB]]

@jw This is what we call ‘expect refinement’ and the compiler is not able to do this.
The commonizer is special and has a way to refine APIs down the line.
This is the first time I see users publicly asking for such a feature for library authors!

[Sebastian Sellmair [JB]]

@russhwolf Really nice trick, btw 😁

[jw]

Oh wow I've had this need for quite some time. I just thought HMPP may have enabled it.

[Sebastian Sellmair [JB]]

No and tbh, there is not even a ticket for this afaik 😕
This indeed was one of the big blocker for commonizing beyond the first level of “common” source sets.
Supporting something like it would not be a lot of effort. We never rejected the idea, but given the efforts for HMPP and the current state of that we think it’s not on the top of the queue 😕

[russhwolf]

If you're ok with another layer of workaround, you could try an opt-in annotation to keep Bar out of public API.

@RequiresOptIn
annotation class InternalApi

@OptIn(InternalApi::class)
actual typealias Foo = Bar

@InternalApi
expect class Bar

But it might not be viable for you because then the new members of Bar are also not public API.

[louiscad]

That annotation can also be made internal to fully prevent opt-in outside the module.

[jw]

Yeah I need them to be public API, unfortunately. I have some workarounds in place by using interfaces which are themselves expect/actual to mix-in the new API but that also creates new public types. At least they're supertypes, though, and not subtypes, so you remain mostly blissfully ignorant of their presence.

[russhwolf]

Oh yeah that's a good trick too