hum, doesn't seem to me this is a bug, when warp is serving using TLS, clients offer Http2 using ALPN, hyper then upgrades the connection to Http2, and per the Http2 spec:

Clients that generate HTTP/2 requests directly SHOULD use the :authority pseudo-header field instead of the Host header field.

accessing the host via Uri::authority() doesn't work for you?
you can get it constructing an Uri with warp::path::full()

Thanks, I will try both when I get home.

I first tried extracting :authority and authority using the warp::header method, to be greeted by identical behaviour of requiring host. For reference, here are my Firefox raw HTTPS request headers:

Host: 127.0.0.1:8080
User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:71.0) Gecko/20100101 Firefox/71.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate, br
Connection: keep-alive
Upgrade-Insecure-Requests: 1
Cache-Control: max-age=0
TE: Trailers

Other info:

Request URL:https://127.0.0.1:8080/invite/4XwS5ZEoVHU
Request Method:GET
Remote Address:127.0.0.1:8080
Status Code:
400
Version:HTTP/2.0

However, warp::path::full() does work! Thanks!

Oops, nevermind. It looks like warp::path::full just returns the path rather than the entire URI (makes sense, given its name).

ah! you are right! warp::path::full doesn't return the Authority
hum, this could solved by making FullPath be

struct FulllPath(String)

instead
and warp::reply::full be

pub fn full() -> impl Filter<Extract = One<FullPath>, Error = Infallible> + Copy {
    filter_fn(move |route| {
        future::ok(one(FullPath(route.uri().to_string())))
    })
}

cc @seanmonstar

We could add a host() filter which checks the URI authority and if not present, checks for the host header (RFC 7230 specifies that order).

Probably return some newtype Host, wrapping a http::uri::Authority?

ah yeah, totally forgot that changing warp::reply::full behavior would be a breaking change, host() filter makes more sense 👍