Is there any way to export kotlin enums? Specially...

# javascript

[Animesh Sahu]

Is there any way to export kotlin enums? Specially in Kt/Multiplatform, should we create js-specific wrapper class for function accepting enum as string, or any better (hacky 😜) way?

[ankushg]

Wondering about the same. Pretty frustrating to deal with enums from Kotlin/JS

[turansky]

Many hacky ways exist
I IR even more

[turansky]

Do you use IR?
Do you need definitions support?

[ankushg]

@turansky do you know of a way that supports IR and TS definitions? That’s currently my biggest blocker for IR

[turansky]

It depends on your case.

In most cases Gradle or Compliler plugin is solution.

Do you have examples of input and required output?

[ankushg]

Right now we have something like enum class ZeroOrTen(val value: Int) { ZERO(0), TEN(10)}

Ideally we would like this to be interoperable with TS in a way that lets clients use 0 and 10 in place of an instance of the class. We currently use Serialization and custom serializers for this but it’s very heavy for client-side JS.

If that’s not possible, maybe
• expose named constants that point to the enum class instances
• use the value field to automatically define a TS enum or union type that we can pass into a function to get an instance of the actual enum class by the value
Currently we can’t even export a function that takes an int and returns an enum because the enum return type can’t be exported.

[Anders]

Has been prototyping with taking mobile common code to the Web. @JsExport and JS/TS interop in general is in an early WIP state — the basic works, but is not yet advanced enough to take production code hassle-free.

Generating or manually writing exportable JS API wrapper seems to be the only satisfactory solution at the moment.

Even if you get around enum classes & other compilation e rror, there are still plenty of issues at runtime awaiting, like https://youtrack.jetbrains.com/issue/KT-45727.

I prototyped codegen using KSP + KotlinPoet, and it seems promising.

Codegen's pragmatic bonus point IMO:
• Don't need to wait for @JsExport to catch up; seems like it is gonna be a long way for stablization before new features even land
• Can contain patches/workarounds of these interop issues, without polluting common code
• Can rewrite select interfaces and (data) classes into external interface , and turn classes into plain JS objects at the API boundary. Useful for React & Web Worker interop.
• Likewise, can rewrite enum classes into e.g. a sealed class hierarchy, or String + generated constants indeed.
• Rewrite suspend methods into Promise<T> returning.
• Rewrite List<T> to Array<T> , etc
Still using manually written wrapper code though. Waiting for the web folks' feedback and decision.

[ankushg]

@Anders -- all of those things sound like things that I'm looking for. Please let me know if there's any way I can contribute to the codegen project!

[turansky]

Unions 🙂
https://pl.kotl.in/4g29mDhLp

Union_kt.kt

[turansky]

Webpack 4+ will inline values

[turansky]

https://twitter.com/vnturansky/status/1386567866523295745