fallback to status code for unmodeled error, cleanup error parser (smithy-lang#565)

Author: AllanZhengYP

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

@@ -2911,8 +2911,9 @@ private String getNumberOutputParam(
     }
 
     /**
-     * Writes the code that loads an {@code errorCode} String with the content used
-     * to dispatch errors to specific serializers.
+     * Writes the code that loads an optional {@code errorCode} String with the content used
+     * to dispatch errors to specific serializers. If an error code cannot be load, the code
+     * must return {@code undefined} so default value can be injected in default case.
      *
      * <p>Two variables will be in scope:
      *   <ul>
@@ -2930,7 +2931,7 @@ private String getNumberOutputParam(
      * <p>For example:
      *
      * <pre>{@code
-     * errorCode = output.headers["x-amzn-errortype"].split(':')[0];
+     * const errorCode = output.headers["x-amzn-errortype"].split(':')[0];
      * }</pre>
      *
      * @param context The generation context.

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

@@ -349,7 +349,6 @@ static Set<StructureShape> generateErrorDispatcher(
             // Error responses must be at least BaseException interface
             SymbolReference baseExceptionReference = getClientBaseException(context);
             writer.write("let response: $T;", baseExceptionReference);
-            writer.write("let errorCode: string = \"UnknownError\";");
             errorCodeGenerator.accept(context);
             writer.openBlock("switch (errorCode) {", "}", () -> {
                 // Generate the case statement for each error, invoking the specific deserializer.
@@ -381,10 +380,14 @@ static Set<StructureShape> generateErrorDispatcher(
 
                         // Get the protocol specific error location for retrieving contents.
                         String errorLocation = bodyErrorLocationModifier.apply(context, "parsedBody");
+                        writer.write("const $$metadata = deserializeMetadata(output);");
+                        writer.write("const statusCode = $$metadata.httpStatusCode ? $$metadata.httpStatusCode"
+                                + " + '' : undefined;");
                         writer.openBlock("response = new $T({", "});", baseExceptionReference, () -> {
-                            writer.write("name: $1L.code || $1L.Code || errorCode,", errorLocation);
+                            writer.write("name: $1L.code || $1L.Code || errorCode || statusCode || 'UnknowError',",
+                                    errorLocation);
                             writer.write("$$fault: \"client\",");
-                            writer.write("$$metadata: deserializeMetadata(output)");
+                            writer.write("$$metadata");
                         });
                         writer.addImport("decorateServiceException", "__decorateServiceException",
                                 TypeScriptDependency.AWS_SMITHY_CLIENT.packageName);

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

@@ -444,8 +444,9 @@ private void readResponseBody(GenerationContext context, OperationShape operatio
     }
 
     /**
-     * Writes the code that loads an {@code errorCode} String with the content used
-     * to dispatch errors to specific serializers.
+     * Writes the code that loads an optional {@code errorCode} String with the content used
+     * to dispatch errors to specific serializers. If an error code cannot be load, the code
+     * must return {@code undefined} so default value can be injected in default case.
      *
      * <p>Two variables will be in scope:
      *   <ul>
@@ -463,7 +464,7 @@ private void readResponseBody(GenerationContext context, OperationShape operatio
      * <p>For example:
      *
      * <pre>{@code
-     * errorCode = output.headers["x-amzn-errortype"].split(':')[0];
+     * const errorCode = output.headers["x-amzn-errortype"].split(':')[0];
      * }</pre>
      *
      * @param context The generation context.