Middleware that change the request body have poor usability #1110
Description
We've heard from several people who try to use tower_http::limit::RequestBodyLimitLayer that the implications are hard to understand.
For example breaking your Router into functions is quite common. Something like:
#[tokio::main]
async fn main() {
let app = my_routes();
let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
axum::Server::bind(&addr)
.serve(app.into_make_service())
.await
.unwrap();
}
fn my_routes() -> Router {
Router::new()
}Adding RequestBodyLimitLayer like so
let app = my_routes().layer(RequestBodyLimitLayer::new(1024));should just work but produces a rather confusing error:
Checking example-hello-world v0.1.0 (/Users/davidpdrsn/dev/major/axum/examples/hello-world)
error[E0277]: the trait bound `Route: tower_service::Service<Request<http_body::limited::Limited<_>>>` is not satisfied
--> hello-world/src/main.rs:13:27
|
13 | let app = my_routes().layer(RequestBodyLimitLayer::new(1024));
| ^^^^^ the trait `tower_service::Service<Request<http_body::limited::Limited<_>>>` is not implemented for `Route`
|
= help: the following implementations were found:
<Route<B, E> as tower_service::Service<Request<B>>>
= note: required because of the requirements on the impl of `tower_service::Service<Request<_>>` for `RequestBodyLimit<Route>`
The solution is instead to write
fn my_routes() -> Router<http_body::Limited<Body>> {
Router::new()
}but that isn't obvious and ideally shouldn't be necessary.
We should think about ways to improve that experience.