Allow handling ErrorCode from outgoing_handler::handle (#121)

* Allow catching `ErrorCode` from `outgoing_handler::handle`

* Test `ErrorCode` handling

* Reformat test file

Author: tomasol

src/http/client.rs

@@ -30,7 +30,7 @@ impl Client {
         let wasi_body = wasi_req.body().unwrap();
 
         // 1. Start sending the request head
-        let res = wasip2::http::outgoing_handler::handle(wasi_req, self.wasi_options()?).unwrap();
+        let res = wasip2::http::outgoing_handler::handle(wasi_req, self.wasi_options()?)?;
 
         let ((), body) = futures_lite::future::try_zip(
             async move {

tests/http_handle_error_code.rs

@@ -0,0 +1,21 @@
+use wstd::http::{Body, Client, Request, error::ErrorCode};
+
+/// Test that `outgoing_handler::handle` errors are properly propagated.
+#[wstd::test]
+async fn handle_returns_error_code() -> Result<(), Box<dyn std::error::Error>> {
+    let request = Request::get("ftp://example.com/").body(Body::empty())?;
+
+    let result = Client::new().send(request).await;
+
+    assert!(
+        result.is_err(),
+        "request with unsupported scheme should fail"
+    );
+    let error = result.unwrap_err();
+    assert!(
+        error.downcast_ref::<ErrorCode>().is_some(),
+        "expected an ErrorCode, got: {error:?}"
+    );
+
+    Ok(())
+}