WIT support via wit-bindgen

[flavio]

Note: this was initially filed as an issue

As part of the WebAssembly Component Model proposal, the WIT format is used to describe the interfaces used by components.

There's a cli tool, wit-bindgen that can to scaffold the import/export code of a certain component.

Currently wit-bindgen can generate export and import code for Wasmtime, but it lacks wasmi support.

In case you're interested, I've created a forked version of wit-bindgen that can generate both import and export code for wasmi.
The code currently lives inside of this repository, under the wasmi branch.

wit-bindgen is undergoing a lot of changes. I've targeted the v0.2.0 release, which is the one used by projects like Spin and SpiderLightning.

I will not push the code upstream yet, because of all these undergoing changes (see this comment).

I'm opening this issue in case other wasmi users could benefit from using this code.

If you want to see the code in action, you can take a look at this codebase.

[Robbepop]

Let me repeat again how cool this is: 🚀🎉
Looking forward to the update that uses the new Linker API for linker based host functions. :)

[flavio]

Good news, I've just updated the wit-bindgen fork to make use of the Linker::func_wrap function introduced by the 0.28.0 release 🥳

[Robbepop]

Hey thanks for letting us know! Have there been any problems or annoyances while using the new API?

[flavio]

Nope, everything worked smoothly 😄

[jakehemmerle]

Nice work!

We're building on substrate, and we're also doing some other Wasm stuff off-chain. So far we've ruled out using wasmi for the offchain part because of no WIT support, but will be reconsidering it if this gets merged, since interpreter is ideal, and could give us the flexability to do WIT on-chain later.

Thanks for the efforts here, I'll be keeping eyes on this! :)

[Robbepop]

I just pinned this discussion for people to get note of it.

See #723 for a usage example with JS types.