Allow .bytes() or .json() not consuming request

[elbaro]

This code sends a request and parse the json response with well-defined error cases.

let response = self
    .http_client
    .execute(req)
    .await
    .context("Sending a request failed")?
    .error_for_status()
    .context("Response Error")?;  // does not have the msg from body data
                                  // only contains a numeric http code

let data: MyResponse = response.json().context("Fail to parse response body")?;

Now I want to report the body in the error contexts, and the code suddenly gets much more complex.
(When the server returns an error, it sends the reason in its body: {'error': 'credential expired'})

Since the error from .json() does not contain the body, this is hard-to-read, verbose, duplicated code.

let response = self
    .http_client
    .execute(req)
    .await
    .context("Sending a request failed")?;

if response.status().is_client_error() || response.status().is_server_error() {
    let status = response.status();  // after .bytes() we cannot read status

    let raw_body = response
        .bytes()
        .await
        .context(Error::ResponseErrorWithEmptyBody{status})?;

    return Err(Error::ResponseError {
        status,
        msg: String::from_utf8_lossy(&raw_body).into_owned(),
    });
}

let raw_body = response  // duplicated because we do not need to call status() in this case
    .bytes()
    .await
    .context("empty body");

let data = serde_json::from_slice::<MyResponse>(&raw_body)
    .context(UnexpectedJsonFormat {
        msg: String::from_utf8_lossy(&raw_body),
    });

Any idea to gracefully achieve this?

[seanmonstar]

That is exactly how I would have suggested to achieve this.

[elbaro]

This is too much for sending 1 request.

Would you consider something like error_for_status_with_body to simplify this pattern?
Looking into the body to learn about the error is not uncommon I think.

let response = self
    .http_client
    .execute(req)
    .await
    .context("Sending a request failed")?
    .error_for_status_with_body() // Error { status_code: usize, body: Option<Vec<u8>> }
    .context("Response Error")?;

// or 
//  .error_for_status_with_details() // Error { status_code: usize, body: Option<Vec<u8>>, headers: .. }