p3(http): `request.new` transmission future resolves to `ok` when `client.send` fails

[saulecabrera]

Consider the following program:

use test_wasm32_wasip3::http::wasi::http::client;
use test_wasm32_wasip3::http::wasi::http::types::{
    ErrorCode, Fields, Method, Request, Response, Scheme,
};
use test_wasm32_wasip3::http::wit_future;
use test_wasm32_wasip3::http::{export, exports::wasi::http::handler::Guest};

struct Component;
export!(Component);

impl Guest for Component {
    async fn handle(_request: Request) -> Result<Response, ErrorCode> {
        let (trailers_tx, trailers_rx) = wit_future::new(|| Ok(None));
        drop(trailers_tx);

        let (request, sent) = Request::new(Fields::new(), None, trailers_rx, None);
        request.set_method(&Method::Get).unwrap();
        request.set_scheme(Some(&Scheme::Http)).unwrap();
        request
            .set_authority(Some("nonexistent.invalid:80"))
            .unwrap();
        request.set_path_with_query(Some("/")).unwrap();

        client::send(request)
            .await
            .expect_err("send to an unresolvable authority should fail");
        assert!(
            sent.await.is_err(),
            "a request that was never transmitted must not report successful transmission"
        );

        let (trailers_tx, trailers_rx) = wit_future::new(|| Ok(None));
        drop(trailers_tx);
        let (response, _sent) = Response::new(Fields::new(), None, trailers_rx);
        response.set_status_code(200).unwrap();
        Ok(response)
    }
}

fn main() {
    unreachable!("main is a stub");
}

It fails the following statement, using wasmtime v46 and main:

 assert!(
            sent.await.is_err(),
            "a request that was never transmitted must not report successful transmission"
        );

Expected behavior

The spec for request.new states:

The returned future resolves to result of transmission of this request

The returned future should resolve to an error, according to the spec.

[saulecabrera]

See WebAssembly/wasi-testsuite#283, for more details (it is essentially the same program linked here). Note that I am assuming that my interpretation of the spec is correct for this particular case, if it is not, I am happy to close this and perhaps move the discussion to the WASI repo.

[alexcrichton]

I suppose the way we're interpreting it in Wasmtime right now is that the future is the result of transmitting the body rather than the entire request, and the result on client::send is the result of sending the request. It wouldn't be too too hard to handle this case within Wasmtime though since the behavior is "something got dropped" and we're able to see that and could synthesize a type of error for "didn't actually succeed"