Revamp error handling model (#402)

* Revamp error handling model

* changelog improvements and typo fixes

* Fix a few more Infallible bounds

* minor docs fixes

examples/key-value-store/src/main.rs

@@ -8,6 +8,7 @@
 
 use axum::{
     body::Bytes,
+    error_handling::HandleErrorLayer,
     extract::{ContentLengthLimit, Extension, Path},
     handler::{delete, get, Handler},
     http::StatusCode,
@@ -18,7 +19,6 @@ use axum::{
 use std::{
     borrow::Cow,
     collections::HashMap,
-    convert::Infallible,
     net::SocketAddr,
     sync::{Arc, RwLock},
     time::Duration,
@@ -52,16 +52,15 @@ async fn main() {
         // Add middleware to all routes
         .layer(
             ServiceBuilder::new()
+                // Handle errors from middleware
+                .layer(HandleErrorLayer::new(handle_error))
                 .load_shed()
                 .concurrency_limit(1024)
                 .timeout(Duration::from_secs(10))
                 .layer(TraceLayer::new_for_http())
                 .layer(AddExtensionLayer::new(SharedState::default()))
                 .into_inner(),
-        )
-        // Handle errors from middleware
-        .handle_error(handle_error)
-        .check_infallible();
+        );
 
     // Run our app with hyper
     let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
@@ -126,20 +125,20 @@ fn admin_routes() -> Router<BoxRoute> {
         .boxed()
 }
 
-fn handle_error(error: BoxError) -> Result<impl IntoResponse, Infallible> {
+fn handle_error(error: BoxError) -> impl IntoResponse {
     if error.is::<tower::timeout::error::Elapsed>() {
-        return Ok((StatusCode::REQUEST_TIMEOUT, Cow::from("request timed out")));
+        return (StatusCode::REQUEST_TIMEOUT, Cow::from("request timed out"));
     }
 
     if error.is::<tower::load_shed::error::Overloaded>() {
-        return Ok((
+        return (
             StatusCode::SERVICE_UNAVAILABLE,
             Cow::from("service is overloaded, try again later"),
-        ));
+        );
     }
 
-    Ok((
+    (
         StatusCode::INTERNAL_SERVER_ERROR,
         Cow::from(format!("Unhandled internal error: {}", error)),
-    ))
+    )
 }