Stream: wasmtime

Topic: Source generated WASI types from another crate

Rohan Krishnaswamy (Feb 07 2024 at 23:36):

Hello!

I'm trying to source WASI types generated by wit_bindgen from another crate, but I'm running into problems. To clarify, the WIT world for my component depends on some WASI types, e.g.:

world my-world {
    use other-types.{outcome};

    use wasi:http/types@0.2.0.{incoming-request};

    import wasi:http/outgoing-handler@0.2.0;

    export handle: func(incoming: incoming-request) -> outcome;
}

When I run wit_bindgen on this world, the generated code includes code for the WASI types/handler. Instead, I'd like to be able to generate the WASI-specific code needed for the component in another crate, and have the component reference it.

A naive approach I took, removing the WASI implementations from the generate code for my-world, and replacing them with references to the corresponding types generated in the dependent crate. This ended up failing with the error when encoding the component:

failed to load xxx: updating metadata for section component-type:internal

Caused by:
    0: failed to merge worlds from two documents
    1: duplicate import found for interface `incoming-request`

For context, the world internal only includes the necessary WASI types (the outgoing-handler, and incoming-request type)

Is there another approach I can take? Is this possible?

Thank you!

Alex Crichton (Feb 08 2024 at 02:52):

What guest language are you using? (assuming guest here because wit_bindgen is being used, but if a host is being used please correct me). If you're using Rust the with option is intended to solve this use case, although it may not be fully complete yet.

Also, if you can, can you capture the inputs to generate that error and file an issue if you get a chance? That's not a great error message and something we should improve

Rohan Krishnaswamy (Feb 08 2024 at 04:02):

Sorry, forgot to mention that my guest language is Rust! Yes, I tried using with but unfortunately I still found that wasi code was still generated. Do you know if there's a workaround in the meantime? FYI, with works as expected in my Rust host environment when using wasmtime::component::bindgen!.

And yes, will definitely file an issue with code to repro!

Alex Crichton (Feb 08 2024 at 04:26):

I'm not aware of a workaround myself, but please feel free to file an issue for this as well

Last updated: Dec 23 2024 at 14:03 UTC