DEBUG-log server request rejections (#2597)

This commit logs server request rejections at the `DEBUG` level in an
operation's `FromRequest` implementation.

This commit is analogous to the one in PR #2524 for response rejections.
However, request rejections are _not_ errors, so they shouldn't be
logged at the `ERROR` level. Indeed, they happen every time the server
rejects a malformed request.

Prior to this commit, the `RuntimeError::NotAcceptable` variant was the
only `RuntimeError` variant that was manually constructed. This commit
makes it so that it now results from a conversion from a new
`RequestRejection::NotAcceptable` variant.

We now leverage `futures_util::future::TryFutureExt::map` to map a
future
that uses `RequestRejection` as its error into a future that uses
`RuntimeError`, and centrally log the rejection there. `futures_util` is
already a transitive dependency of server SDKs (via e.g. `hyper` and
`tower`), so adding it is a direct dependency is not worse.

This helps with #2521.

----

_By submitting this pull request, I confirm that you can use, modify,
copy, and redistribute this contribution, under the terms of your
choice._

codegen-server/src/main/kotlin/software/amazon/smithy/rust/codegen/server/smithy/ServerCargoDependency.kt

@@ -17,6 +17,7 @@ import software.amazon.smithy.rust.codegen.core.smithy.RuntimeConfig
 object ServerCargoDependency {
     val AsyncTrait: CargoDependency = CargoDependency("async-trait", CratesIo("0.1"))
     val FormUrlEncoded: CargoDependency = CargoDependency("form_urlencoded", CratesIo("1"))
+    val FuturesUtil: CargoDependency = CargoDependency("futures-util", CratesIo("0.3"))
     val Mime: CargoDependency = CargoDependency("mime", CratesIo("0.3"))
     val Nom: CargoDependency = CargoDependency("nom", CratesIo("7"))
     val OnceCell: CargoDependency = CargoDependency("once_cell", CratesIo("1.13"))

codegen-server/src/main/kotlin/software/amazon/smithy/rust/codegen/server/smithy/protocols/ServerHttpBoundProtocolGenerator.kt

@@ -137,6 +137,7 @@ class ServerHttpBoundProtocolTraitImplGenerator(
         "Cow" to RuntimeType.Cow,
         "DateTime" to RuntimeType.dateTime(runtimeConfig),
         "FormUrlEncoded" to ServerCargoDependency.FormUrlEncoded.toType(),
+        "FuturesUtil" to ServerCargoDependency.FuturesUtil.toType(),
         "HttpBody" to RuntimeType.HttpBody,
         "header_util" to RuntimeType.smithyHttp(runtimeConfig).resolve("header"),
         "Hyper" to RuntimeType.Hyper,
@@ -182,7 +183,7 @@ class ServerHttpBoundProtocolTraitImplGenerator(
                 rustTemplate(
                     """
                     if !#{SmithyHttpServer}::protocols::accept_header_classifier(request.headers(), ${contentType.dq()}) {
-                        return Err(#{RuntimeError}::NotAcceptable)
+                        return Err(#{RequestRejection}::NotAcceptable);
                     }
                     """,
                     *codegenScope,
@@ -201,9 +202,7 @@ class ServerHttpBoundProtocolTraitImplGenerator(
                             ?.let { "Some(${it.dq()})" } ?: "None"
                         rustTemplate(
                             """
-                            if #{SmithyHttpServer}::protocols::content_type_header_classifier(request.headers(), $expectedRequestContentType).is_err() {
-                                return Err(#{RuntimeError}::UnsupportedMediaType)
-                            }
+                            #{SmithyHttpServer}::protocols::content_type_header_classifier(request.headers(), $expectedRequestContentType)?;
                             """,
                             *codegenScope,
                         )
@@ -213,9 +212,9 @@ class ServerHttpBoundProtocolTraitImplGenerator(
 
         // Implement `from_request` trait for input types.
         val inputFuture = "${inputSymbol.name}Future"
+        // TODO(https://github.com/awslabs/smithy-rs/issues/2238): Remove the `Pin<Box<dyn Future>>` and replace with thin wrapper around `Collect`.
         rustTemplate(
             """
-            // TODO(https://github.com/awslabs/smithy-rs/issues/2238): Remove the `Pin<Box<dyn Future>>` and replace with thin wrapper around `Collect`.
             #{PinProjectLite}::pin_project! {
                 /// A [`Future`](std::future::Future) aggregating the body bytes of a [`Request`] and constructing the
                 /// [`${inputSymbol.name}`](#{I}) using modelled bindings.
@@ -252,13 +251,17 @@ class ServerHttpBoundProtocolTraitImplGenerator(
                             .await
                             .map_err(Into::into)
                     };
+                    use #{FuturesUtil}::future::TryFutureExt;
+                    let fut = fut.map_err(|e: #{RequestRejection}| {
+                        #{Tracing}::debug!(error = %e, "failed to deserialize request");
+                        #{RuntimeError}::from(e)
+                    });
                     $inputFuture {
                         inner: Box::pin(fut)
                     }
                 }
             }
-
-            """.trimIndent(),
+            """,
             *codegenScope,
             "I" to inputSymbol,
             "Marker" to protocol.markerStruct(),

rust-runtime/aws-smithy-http-server/src/proto/aws_json/rejection.rs

@@ -18,6 +18,8 @@ pub enum ResponseRejection {
 pub enum RequestRejection {
     #[error("error converting non-streaming body to bytes: {0}")]
     BufferHttpBodyBytes(crate::Error),
+    #[error("request contains invalid value for `Accept` header")]
+    NotAcceptable,
     #[error("expected `Content-Type` header not found: {0}")]
     MissingContentType(#[from] MissingContentTypeReason),
     #[error("error deserializing request HTTP body as JSON: {0}")]

rust-runtime/aws-smithy-http-server/src/proto/rest_json_1/rejection.rs

@@ -109,6 +109,11 @@ pub enum RequestRejection {
     #[error("error converting non-streaming body to bytes: {0}")]
     BufferHttpBodyBytes(crate::Error),
 
+    /// Used when the request contained an `Accept` header with a MIME type, and the server cannot
+    /// return a response body adhering to that MIME type.
+    #[error("request contains invalid value for `Accept` header")]
+    NotAcceptable,
+
     /// Used when checking the `Content-Type` header.
     #[error("expected `Content-Type` header not found: {0}")]
     MissingContentType(#[from] MissingContentTypeReason),

rust-runtime/aws-smithy-http-server/src/proto/rest_json_1/runtime_error.rs

@@ -115,6 +115,7 @@ impl From<RequestRejection> for RuntimeError {
         match err {
             RequestRejection::MissingContentType(_reason) => Self::UnsupportedMediaType,
             RequestRejection::ConstraintViolation(reason) => Self::Validation(reason),
+            RequestRejection::NotAcceptable => Self::NotAcceptable,
             _ => Self::Serialization(crate::Error::new(err)),
         }
     }

rust-runtime/aws-smithy-http-server/src/proto/rest_xml/rejection.rs

@@ -28,6 +28,9 @@ pub enum RequestRejection {
     #[error("error converting non-streaming body to bytes: {0}")]
     BufferHttpBodyBytes(crate::Error),
 
+    #[error("request contains invalid value for `Accept` header")]
+    NotAcceptable,
+
     #[error("expected `Content-Type` header not found: {0}")]
     MissingContentType(#[from] MissingContentTypeReason),