Update Error handling through async

This commit includes updates to handling errors to allow for streaming
error body members. It also includes minor fixes for unused properties.

Author: kstich

smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/integration/HttpBindingProtocolGenerator.java

@@ -592,11 +592,10 @@ private void generateErrorDeserializer(GenerationContext context, StructureShape
         String errorDeserMethodName = ProtocolGenerator.getDeserFunctionName(errorSymbol,
                 context.getProtocolName()) + "Response";
 
-        writer.openBlock("const $L = (\n"
+        writer.openBlock("const $L = async (\n"
                        + "  output: any,\n"
                        + "  context: __SerdeContext\n"
-                       + "): $T => {", "};", errorDeserMethodName, errorSymbol, () -> {
-
+                       + "): Promise<$T> => {", "};", errorDeserMethodName, errorSymbol, () -> {
             writer.openBlock("const contents: $T = {", "};", errorSymbol, () -> {
                 writer.write("__type: $S,", error.getId().getName());
                 writer.write("$$fault: $S,", error.getTrait(ErrorTrait.class).get().getValue());
@@ -677,6 +676,25 @@ private List<HttpBinding> readResponseBody(
         documentBindings.sort(Comparator.comparing(HttpBinding::getMemberName));
         List<HttpBinding> payloadBindings = bindingIndex.getResponseBindings(operationOrError, Location.PAYLOAD);
 
+        if (!documentBindings.isEmpty()) {
+            readReponseBodyData(context, operationOrError);
+            deserializeOutputDocument(context, operationOrError, documentBindings);
+            return documentBindings;
+        }
+        if (!payloadBindings.isEmpty()) {
+            readReponseBodyData(context, operationOrError);
+            // There can only be one payload binding.
+            HttpBinding binding = payloadBindings.get(0);
+            Shape target = context.getModel().expectShape(binding.getMember().getTarget());
+            writer.write("contents.$L = $L;", binding.getMemberName(), getOutputValue(context,
+                    Location.PAYLOAD, "data", binding.getMember(), target));
+            return payloadBindings;
+        }
+        return ListUtils.of();
+    }
+
+    private void readReponseBodyData(GenerationContext context, Shape operationOrError) {
+        TypeScriptWriter writer = context.getWriter();
         // Prepare response body for deserializing.
         OperationIndex operationIndex = context.getModel().getKnowledge(OperationIndex.class);
         StructureShape operationOutputOrError = operationOrError.asStructureShape()
@@ -692,20 +710,6 @@ private List<HttpBinding> readResponseBody(
             // Otherwise, we collect the response body to structured object with parseBody().
             writer.write("const data: any = await parseBody(output.body, context);");
         }
-
-        if (!documentBindings.isEmpty()) {
-            deserializeOutputDocument(context, operationOrError, documentBindings);
-            return documentBindings;
-        }
-        if (!payloadBindings.isEmpty()) {
-            // There can only be one payload binding.
-            HttpBinding binding = payloadBindings.get(0);
-            Shape target = context.getModel().expectShape(binding.getMember().getTarget());
-            writer.write("contents.$L = $L;", binding.getMemberName(), getOutputValue(context,
-                    Location.PAYLOAD, "data", binding.getMember(), target));
-            return payloadBindings;
-        }
-        return ListUtils.of();
     }
 
     /**

smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/integration/HttpProtocolGeneratorUtils.java

@@ -26,6 +26,7 @@
 import software.amazon.smithy.model.shapes.Shape;
 import software.amazon.smithy.model.shapes.StructureShape;
 import software.amazon.smithy.model.traits.TimestampFormatTrait.Format;
+import software.amazon.smithy.typescript.codegen.TypeScriptDependency;
 import software.amazon.smithy.typescript.codegen.TypeScriptWriter;
 import software.amazon.smithy.typescript.codegen.integration.ProtocolGenerator.GenerationContext;
 
@@ -146,7 +147,13 @@ static Set<StructureShape> generateErrorDispatcher(
                     writer.write("body: data,");
                 });
             }
-            writer.write("let response: any;");
+
+            // Error responses must be at least SmithyException and MetadataBearer implementations.
+            writer.addImport("SmithyException", "__SmithyException",
+                    TypeScriptDependency.AWS_SMITHY_CLIENT.packageName);
+            writer.addImport("MetadataBearer", "__MetadataBearer",
+                    TypeScriptDependency.AWS_SDK_TYPES.packageName);
+            writer.write("let response: __SmithyException & __MetadataBearer;");
             writer.write("let errorCode: String;");
             errorCodeGenerator.accept(context);
             writer.openBlock("switch (errorCode) {", "}", () -> {
@@ -160,7 +167,7 @@ static Set<StructureShape> generateErrorDispatcher(
                             context.getProtocolName()) + "Response";
                     writer.openBlock("case $S:\ncase $S:", "  break;", errorId.getName(), errorId.toString(), () -> {
                         // Dispatch to the error deserialization function.
-                        writer.write("response = $L(parsedOutput, context);", errorDeserMethodName);
+                        writer.write("response = await $L(parsedOutput, context);", errorDeserMethodName);
                     });
                 });
 
@@ -169,8 +176,8 @@ static Set<StructureShape> generateErrorDispatcher(
                         .write("errorCode = errorCode || \"UnknownError\";")
                         .openBlock("response = {", "};", () -> {
                             writer.write("__type: `$L#$${errorCode}`,", operation.getId().getNamespace());
-                            writer.write("$$name: errorCode,");
                             writer.write("$$fault: \"client\",");
+                            writer.write("$$metadata: deserializeMetadata(output),");
                         }).dedent();
             });
             writer.write("return Promise.reject(Object.assign(new Error(response.__type), response));");

smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/integration/HttpRpcProtocolGenerator.java

@@ -238,8 +238,6 @@ private void generateOperationDeserializer(GenerationContext context, OperationS
             });
 
             // Start deserializing the response.
-            writer.write("const data: any = await parseBody(output.body, context)");
-            writer.write("let contents: any = {};");
             readResponseBody(context, operation);
 
             // Build the response with typing and metadata.
@@ -270,10 +268,10 @@ private void generateErrorDeserializer(GenerationContext context, StructureShape
         // Add the error shape to the list to generate functions for, since we'll use that.
         deserializingDocumentShapes.add(error);
 
-        writer.openBlock("const $L = (\n"
+        writer.openBlock("const $L = async (\n"
                        + "  output: any,\n"
                        + "  context: __SerdeContext\n"
-                       + "): $T => {", "};", errorDeserMethodName, errorSymbol, () -> {
+                       + "): Promise<$T> => {", "};", errorDeserMethodName, errorSymbol, () -> {
             // First deserialize the body properly.
             writer.write("const deserialized: any = $L(output.body, context);",
                     ProtocolGenerator.getDeserFunctionName(errorSymbol, context.getProtocolName()));
@@ -294,6 +292,11 @@ private void generateErrorDeserializer(GenerationContext context, StructureShape
 
     private void readResponseBody(GenerationContext context, OperationShape operation) {
         operation.getOutput().ifPresent(outputId -> {
+            // We only need to load the body and prepare a contents object if there is a response.
+            TypeScriptWriter writer = context.getWriter();
+            writer.write("const data: any = await parseBody(output.body, context)");
+            writer.write("let contents: any = {};");
+
             // If there's an output present, we know it's a structure.
             StructureShape outputShape = context.getModel().expectShape(outputId).asStructureShape().get();