Stream: wasi

Topic: wasi-http Request and pub(crate) Body

Theodore Brockman (Oct 07 2025 at 21:02):

It seems like based on its visibility that I'm not supposed to be directly interacting with the Body of a wasmtime_wasi_http::p3::Request, but in my case I certainly would like to (which makes me think that I'm probably not doing the correct thing -- and if so would greatly appreciate learning the error of my ways!)

I have a list of event handler components which each satisfy the following interface, where each may either short-circuit and return a request/response (HandleRequestResult::Done(req_or_res)), or pass on a potentially modified request to future handlers (HandleRequestResult::Next(req)):

interface event-handler {
    use wasi:http/types@0.3.0-rc-2025-09-16.{request, response};
    use capabilities.{capability-provider};

    variant request-or-response {
        request(request),
        response(response),
    }

    variant handle-request-result {
        next(request),
        done(request-or-response),
    }

    handle-request: func(r: request, cp: capability-provider) -> handle-request-result;

   // ...other stuff unrelated to the question
}

In the case of the end result of the chain being a request (not response), from the host side I'd like to execute the resulting wasmtime_wasi_http::p3::Request, but it seems like in order to do that I'd need to have access to the request Body, or use existing wasi-http code by passing it to a simple proxy handler component which just performs the request (though this seems a bit unusual).

Does this sound right? Is there a better/easier way of doing this?

Alex Crichton (Oct 07 2025 at 22:23):

I think you're running into a limitation of the wasmtime-wasi-http crate itself which is a bug we should fix! IMO what you want is Request::into_http akin to Response::into_http. My guess is it would probably function more-or-less the same way, so in theory shouldn't be too hard to add

Theodore Brockman (Oct 07 2025 at 22:39):

Okay, I'll mess around with that and can send in a PR if it ends up being legible :grimacing:

Theodore Brockman (Nov 20 2025 at 21:34):

@Alex Crichton Somewhat similar here, would there be any objection to a Response::from_http method (for passing a preexisting HTTP response to a guest)?

Alex Crichton (Nov 20 2025 at 21:35):

yeah seems reasonable to me!

Last updated: Dec 06 2025 at 06:05 UTC