Forward request body to response in Actix-Web - asynchronous

Question

I would like to forward the Actix-Web request body to the response body (something like echo) but it gives a mismatched types error.
use actix_web::*;
use futures::future::ok;
use futures::Future;
fn show_request(
request: &actix_web::HttpRequest
) -> Box<Future<Item=HttpResponse, Error=Error>> {
request
.body()
.from_err::<actix_web::error::PayloadError>()
.map(move |f| {
Box::new(ok(actix_web::HttpResponse::Ok()
.content_type("text/plain")
.body(f)))
})
}
pub fn index(scope: actix_web::Scope<()>) -> actix_web::Scope<()> {
scope.handler("", |req: &actix_web::HttpRequest| {
show_request(req)
})
}
fn main() {
actix_web::server::new(|| {
vec![
actix_web::App::new()
.scope("", index)
.boxed(),
]
}).bind("127.0.0.1:8000")
.expect("Can not bind to port 8000")
.run();
}
[package]
name = "temp"
version = "0.1.0"
authors = ["John"]
edition = "2018"
[dependencies]
actix-web = "0.7"
futures = "0.1"
error:
error[E0308]: mismatched types
--> src/proj.rs:50:2
|
49 | ) -> Box<Future<Item=HttpResponse, Error=Error>> {
| ------------------------------------------- expected `std::boxed::Box<(dyn futures::Future<Error=actix_web::Error, Item=actix_web::HttpResponse> + 'static)>` because of return type
50 | request
| _____^
51 | | .body()
52 | | .from_err::<actix_web::error::PayloadError>()
53 | | .map(move |f| {
... |
56 | | .body(f)))
57 | | })
| |__________^ expected struct `std::boxed::Box`, found struct `futures::Map`
|
= note: expected type `std::boxed::Box<(dyn futures::Future<Error=actix_web::Error, Item=actix_web::HttpResponse> + 'static)>`
found type `futures::Map<futures::future::FromErr<actix_web::dev::MessageBody<actix_web::HttpRequest>, actix_web::error::PayloadError>, [closure#src/.rs:53:8: 57:4]>`
Why does this error occur and how can I fix it?

Answer 1

You are trying to return a Future without Boxing, you are Boxing the response in Map's closure, not the expected Future. Using futures::future::ok is not necessary because your request.body is already future.
fn show_request(
request: &actix_web::HttpRequest,
) -> Box<Future<Item = HttpResponse, Error = Error>> {
Box::new(request.body().map_err(|e| e.into()).map(move |f| {
actix_web::HttpResponse::Ok()
.content_type("text/plain")
.body(f)
}))
}