`.map` reply with a Future.

[seanmonstar]

`.map` reply with a Future.

[seanmonstar]

The and_then combinator is meant for returning a Future. The validation part is just that a user needs to explicitly handle their Future's error, and convert it into an appropriate rejection (or reply, if that's preferred).

[norcalli]

Ah, ok. I got it working, I believe. Essentially, as long as I map_err into warp::reject() or the like, it's accepted. The error message was a bit opaque, especially since CombineRejection is a sealed trait. For future reference, this is a working snippet from my code:

use std::time::Duration;

use futures::prelude::*;
use futures_timer::Delay;

use warp::Filter;

fn gpu_task(input: String) -> impl Future<Item = String> {
    Delay::new(Duration::from_millis(100)).map(move |()| input)
}

fn main() {
    let route = warp::path("batch")
        .and(warp::filters::body::json())
        .and_then(|input: String| {
            gpu_task(input)
                .map(|output| warp::reply::json(&output))
                .map_err(|_| warp::reject::server_error())
        });

    warp::serve(route).run(([0; 4], 3030));
}