Explore Kotlin/Wasm support using WASI

[sdeleuze]

This is obviously still the early days of Kotlin/Wasm which is not yet really usable, but be aware I would like to begin exploring Kotlin/Wasm support using WASI. I am initially experimenting on https://github.com/sdeleuze/kowasm/ side (see kowasm/kowasm#9 related issue) and then later would like to contribute a PR here when Kotlin/Wasm will be more mature and WASI supported out of the box (may take some time).

Any thoughts from your team on a potential future WASI support? Is there anything preventing me creating an experimental Kotlin/Wasm + WASI support in an external repository?

[dkhalanskyjb]

https://github.com/Kotlin/kotlinx-datetime/tree/0f4c62d32d87b35d8af54b408ed8685d0ddfd18a/core/native/src this (in combination with https://github.com/Kotlin/kotlinx-datetime/tree/0f4c62d32d87b35d8af54b408ed8685d0ddfd18a/core/common) contains the pure Kotlin implementation of everything in kotlinx-datetime, except for the things listed here: https://github.com/Kotlin/kotlinx-datetime/blob/0f4c62d32d87b35d8af54b408ed8685d0ddfd18a/core/native/cinterop/public/cdate.h They have to be provided by the platform. If you can implement all the declarations listed there, nothing prevents you from having a WASI target.

[sdeleuze]

I initially tried to fork the repository, updating it to use Kotlin 1.8.20 dev build, but the lack of Kotlinx.serialization support + other issues related to the fact that core/native/src is currently designed for native (probably solvable via a refined hierarchical project structure) made it too difficult.

So for now via this commit I just copied core/native/src and core/common, implemented currentTime() with WASI, and provided an implementation of RegionTimeZone that throws UnsupportedOperationException, and it seems to work pretty fine expect for timezones.

Edit : now available in a dedicated module

[sdeleuze]

Timezone support should be available as of WASI Preview2, see WebAssembly/wasi-clocks#25 related issue.

[dkhalanskyjb]

Closing in favor of the more general #324