fix(client): no keep-alive always returning an error

[dswij]

fixes hyperium/hyper#3499

This PR fixes the hyper_util::client::legacy::Client always returning an error without sending any request.

Found while working on #77, test for this will be included in the PR.

---

After the change, the code in the issue returns

Ok(
    Response {
        status: 200,
        version: HTTP/1.0,
        headers: {
            "server": "SimpleHTTP/0.6 Python/3.11.4",
            "date": "Fri, 22 Dec 2023 13:24:20 GMT",
            "content-type": "text/html; charset=utf-8",
            "content-length": "2204",
        },
        body: Body(
            Streaming,
        ),
    },
)

instead of PoolDisabled error

[seanmonstar]

Hm, there's this code in the repo already:

            Either::Left((Err(err), connecting)) => {
                if err.is_canceled() {
                    connecting.await.map_err(ClientConnectError::Normal)
                } else {
                    Err(ClientConnectError::Normal(e!(Connect, err)))
                }
            }

Is the problem that the pool disabled error no longer results in err.is_canceled() being true?

[dswij]

Is the problem that the pool disabled error no longer results in err.is_canceled() being true?

Yes.

But doing it this way is kinda confusing. Explicitly selecting one future in this case instead of saying it's canceled is clearer in my opinion.

[seanmonstar]

Agreed, this is clearer. As long no extra logic that should apply in both cases happens down in the select.