feat(type-safe-api): include error header expected by smithy generate…

…d client in handler wrappers (#468)

Clients generated directly from Smithy (using the typescript-codegen plugin) can deserialise error
responses into the appropriate generated model classes, but they do this by checking for a special
`x-amzn-errortype` header. This change updates the generated handler wrappers to include the
appropriate value for this header for error responses. Note that OpenAPI specs generated from Smithy
add "ResponseContent" as a suffix to all response data types, so we remove this in order to match
the appropriate error structure ID. If the response data type doesn't end with ResponseContent, it
didn't come from Smithy so there's no need to return this header anyway.

re #460

packages/type-safe-api/scripts/generators/java/templates/handlers.mustache

@@ -257,6 +257,11 @@ public class Handlers {
         private {{operationIdCamelCase}}{{code}}Response({{#dataType}}final {{#isPrimitiveType}}String{{/isPrimitiveType}}{{^isPrimitiveType}}{{.}}{{/isPrimitiveType}} body, {{/dataType}}final Map<String, String> headers) {
             this.body = {{#dataType}}{{#isPrimitiveType}}body{{/isPrimitiveType}}{{^isPrimitiveType}}body.toJson(){{/isPrimitiveType}}{{/dataType}}{{^dataType}}""{{/dataType}};
             this.headers = headers;
+            {{^is2xx}}
+            if ("{{dataType}}".endsWith("ResponseContent")) {
+                this.headers.put("x-amzn-errortype", "{{dataType}}".substring(0, "{{dataType}}".length() - "ResponseContent".length()));
+            }
+            {{/is2xx}}
         }
 
         @Override

packages/type-safe-api/scripts/generators/python/templates/operationConfig.mustache

@@ -229,13 +229,18 @@ def {{operationId}}_handler(_handler: {{operationIdCamelCase}}HandlerFunction =
                 interceptor_context,
             ), **kwargs)
 
+            response_headers = response.headers or {}
             response_body = ''
             if response.body is None:
                 pass
             {{#responses}}
             elif response.status_code == {{code}}:
                 {{^isPrimitiveType}}
                 response_body = json.dumps(JSONEncoder().default(response.body))
+                {{^is2xx}}
+                if "{{dataType}}".endswith("ResponseContent"):
+                    response_headers["x-amzn-errortype"] = "{{dataType}}"[:-len("ResponseContent")]
+                {{/is2xx}}
                 {{/isPrimitiveType}}
                 {{#isPrimitiveType}}
                 response_body = response.body
@@ -244,7 +249,7 @@ def {{operationId}}_handler(_handler: {{operationIdCamelCase}}HandlerFunction =
 
             return {
                 'statusCode': response.status_code,
-                'headers': response.headers,
+                'headers': response_headers,
                 'body': response_body,
             }
         return wrapper

packages/type-safe-api/scripts/generators/typescript/templates/operationConfig.mustache

@@ -270,8 +270,33 @@ export const {{nickname}}Handler = (
         return marshalledBody;
     };
 
+    const errorHeaders = (statusCode: number): { [key: string]: string } => {
+        let headers = {};
+
+        switch(statusCode) {
+        {{#responses}}
+        {{^is2xx}}
+            case {{code}}: {
+                if ("{{dataType}}".endsWith("ResponseContent")) {
+                    headers["x-amzn-errortype"] = "{{dataType}}".slice(0, -"ResponseContent".length);
+                }
+                break;
+            }
+        {{/is2xx}}
+        {{/responses}}
+            default:
+                break;
+        }
+
+        return headers;
+    };
+
     return {
         ...response,
+        headers: {
+          ...errorHeaders(response.statusCode),
+          ...response.headers,
+        },
         body: response.body ? marshal(response.statusCode, response.body) : '',
     };
 };