Render full shape IDs in server error responses

RestJson1 implementations can denote errors in responses in several
ways. New server-side protocol implementations MUST use a header field
named `X-Amzn-Errortype`.

Note that the spec says that implementations SHOULD strip the error
shape ID's namespace. However, our server implementation renders the
full shape ID (including namespace), since some existing clients rely on
it to deserialize the error shape and fail if only the shape name is
present. This is compliant with the spec, see
smithy-lang/smithy#1493.

See smithy-lang/smithy#1494 too.

codegen-core/common-test-models/rest-json-extras.smithy

@@ -80,12 +80,16 @@ service RestJsonExtras {
         appliesTo: "client",
     },
     {
-        documentation: "Upper case error modeled lower case",
+        documentation: """
+            Upper case error modeled lower case.
+            Servers render the full shape ID (including namespace), since some
+            existing clients rely on it to deserialize the error shape and fail
+            if only the shape name is present.""",
         id: "ServiceLevelErrorServer",
         protocol: "aws.protocols#restJson1",
         code: 500,
         body: "{}",
-        headers: { "X-Amzn-Errortype": "ExtraError" },
+        headers: { "X-Amzn-Errortype": "aws.protocoltests.restjson#ExtraError" },
         params: {},
         appliesTo: "server",
     }

codegen-core/src/main/kotlin/software/amazon/smithy/rust/codegen/core/smithy/protocols/RestJson.kt

@@ -81,9 +81,15 @@ open class RestJson(val codegenContext: CodegenContext) : Protocol {
     /**
      * RestJson1 implementations can denote errors in responses in several ways.
      * New server-side protocol implementations MUST use a header field named `X-Amzn-Errortype`.
+     *
+     * Note that the spec says that implementations SHOULD strip the error shape ID's namespace.
+     * However, our server implementation renders the full shape ID (including namespace), since some
+     * existing clients rely on it to deserialize the error shape and fail if only the shape name is present.
+     * This is compliant with the spec, see https://github.com/awslabs/smithy/pull/1493.
+     * See https://github.com/awslabs/smithy/issues/1494 too.
      */
     override fun additionalErrorResponseHeaders(errorShape: StructureShape): List<Pair<String, String>> =
-        listOf("x-amzn-errortype" to errorShape.id.name)
+        listOf("x-amzn-errortype" to errorShape.id.toString())
 
     override fun structuredDataParser(operationShape: OperationShape): StructuredDataParserGenerator =
         JsonParserGenerator(codegenContext, httpBindingResolver, ::restJsonFieldName)

codegen-server/src/main/kotlin/software/amazon/smithy/rust/codegen/server/smithy/generators/protocol/ServerProtocolTestGenerator.kt

@@ -1194,6 +1194,13 @@ class ServerProtocolTestGenerator(
         ): HttpRequestTestCase =
             testCase.toBuilder().putHeader("x-amz-target", "JsonProtocol.${operationShape.id.name}").build()
 
+        private fun fixRestJsonInvalidGreetingError(testCase: HttpResponseTestCase): HttpResponseTestCase =
+            testCase.toBuilder().putHeader("X-Amzn-Errortype", "aws.protocoltests.restjson#InvalidGreeting").build()
+        private fun fixRestJsonEmptyComplexErrorWithNoMessage(testCase: HttpResponseTestCase): HttpResponseTestCase =
+            testCase.toBuilder().putHeader("X-Amzn-Errortype", "aws.protocoltests.restjson#ComplexError").build()
+        private fun fixRestJsonComplexErrorWithNoMessage(testCase: HttpResponseTestCase): HttpResponseTestCase =
+            testCase.toBuilder().putHeader("X-Amzn-Errortype", "aws.protocoltests.restjson#ComplexError").build()
+
         // These are tests whose definitions in the `awslabs/smithy` repository are wrong.
         // This is because they have not been written from a server perspective, and as such the expected `params` field is incomplete.
         // TODO(https://github.com/awslabs/smithy-rs/issues/1288): Contribute a PR to fix them upstream.
@@ -1270,6 +1277,11 @@ class ServerProtocolTestGenerator(
         )
 
         private val BrokenResponseTests: Map<Pair<String, String>, KFunction1<HttpResponseTestCase, HttpResponseTestCase>> =
-            mapOf()
+            // TODO(https://github.com/awslabs/smithy/issues/1494)
+            mapOf(
+                Pair(RestJson, "RestJsonInvalidGreetingError") to ::fixRestJsonInvalidGreetingError,
+                Pair(RestJson, "RestJsonEmptyComplexErrorWithNoMessage") to ::fixRestJsonEmptyComplexErrorWithNoMessage,
+                Pair(RestJson, "RestJsonComplexErrorWithNoMessage") to ::fixRestJsonComplexErrorWithNoMessage,
+            )
     }
 }

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

@@ -32,6 +32,7 @@ import software.amazon.smithy.rust.codegen.core.rustlang.RustWriter
 import software.amazon.smithy.rust.codegen.core.rustlang.Writable
 import software.amazon.smithy.rust.codegen.core.rustlang.asType
 import software.amazon.smithy.rust.codegen.core.rustlang.conditionalBlock
+import software.amazon.smithy.rust.codegen.core.rustlang.escape
 import software.amazon.smithy.rust.codegen.core.rustlang.render
 import software.amazon.smithy.rust.codegen.core.rustlang.rust
 import software.amazon.smithy.rust.codegen.core.rustlang.rustBlock
@@ -635,7 +636,7 @@ private class ServerHttpBoundProtocolTraitImplGenerator(
                     builder = #{header_util}::set_response_header_if_absent(
                         builder,
                         http::header::HeaderName::from_static("$headerName"),
-                        "$headerValue"
+                        "${escape(headerValue)}"
                     );
                     """,
                     *codegenScope,