How to inspect the absolutely final response?

[svenstaro]

When I use a middleware like so:

impl<S, ReqBody, ResBody> Service<Request<ReqBody>> for MyMiddleware<S>
where
    S: Service<Request<ReqBody>, Response = Response<ResBody>> + Clone + Send + 'static,
    S::Future: Send + 'static,
    ReqBody: Send + 'static,
    ResBody: Send + 'static,
{
    type Response = S::Response;
    type Error = S::Error;
    type Future = BoxFuture<'static, Result<Self::Response, Self::Error>>;

    fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
        self.inner.poll_ready(cx)
    }

    fn call(&mut self, mut req: Request<ReqBody>) -> Self::Future {
        let clone = self.inner.clone();
        let mut inner = std::mem::replace(&mut self.inner, clone);

        Box::pin(async move {
            let res: Response<ResBody> = inner.call(req).await?;
            dbg!(res.headers());
            Ok(res)
        })
    }
}

The dbg!() will show:

res.headers() = {
    "content-type": "text/plain",
}

However, a curl -v will clearly show that the request is still being tampered with after this stage:

< HTTP/1.1 200 OK
< content-type: text/plain
< content-length: 22
< date: Tue, 24 Aug 2021 02:49:26 GMT

How can I get the absolutely final request data (read-only is fine) before the request is sent out to the client?

To be clear: For informational purposes my tool needs to show exactly which headers are about to be sent just as that happens.

[davidpdrsn]

I'm actually not sure that's possible 🤔 It is hyper that is tampering with the request before sending it. I would recommend you ask in hypers discord channel

[svenstaro]

Alright, seems I'll move the question over there.