invert condition to restore type narrowing, extract error templating

Author: EzraBrooks

src/core/Action.ts

@@ -14,6 +14,28 @@ import {
 import type Ros from "./Ros.ts";
 import { v4 as uuidv4 } from "uuid";
 
+class GoalError extends Error {
+  override name = "GoalError";
+  constructor(status: GoalStatus, errorValue?: string) {
+    super(`${makeErrorMessage(status)}${errorValue ? `: ${errorValue}` : ""}`);
+  }
+}
+
+function makeErrorMessage(status: GoalStatus) {
+  switch (status) {
+    case GoalStatus.STATUS_CANCELED:
+      return `Action was canceled`;
+    case GoalStatus.STATUS_ABORTED:
+      return `Action was aborted`;
+    case GoalStatus.STATUS_CANCELING:
+      return `Action is canceling`;
+    case GoalStatus.STATUS_UNKNOWN:
+      return `Action status unknown`;
+    default:
+      return `Action failed with status ${String(status)}`;
+  }
+}
+
 /**
  * A ROS 2 action client.
  */
@@ -73,32 +95,15 @@ export default class Action<
       if (isRosbridgeActionResultMessage<TResult>(message)) {
         const status = message.status as GoalStatus;
 
-        // Check status code instead of result field to properly handle STATUS_CANCELED
-        if (status === GoalStatus.STATUS_SUCCEEDED && message.result) {
-          resultCallback(message.values);
+        if (!message.result) {
+          failedCallback(String(new GoalError(status, message.values)));
+        } else if (status !== GoalStatus.STATUS_SUCCEEDED) {
+          failedCallback(
+            String(new GoalError(status, JSON.stringify(message.values))),
+          );
+          // Check status code instead of result field to properly handle STATUS_CANCELED
         } else {
-          const baseError =
-            typeof message.values === "string" ? message.values : "";
-
-          let errorMessage: string;
-          switch (status) {
-            case GoalStatus.STATUS_CANCELED:
-              errorMessage = `Action was canceled${baseError ? `: ${baseError}` : ""}`;
-              break;
-            case GoalStatus.STATUS_ABORTED:
-              errorMessage = `Action was aborted${baseError ? `: ${baseError}` : ""}`;
-              break;
-            case GoalStatus.STATUS_CANCELING:
-              errorMessage = `Action is canceling${baseError ? `: ${baseError}` : ""}`;
-              break;
-            case GoalStatus.STATUS_UNKNOWN:
-              errorMessage = `Action status unknown${baseError ? `: ${baseError}` : ""}`;
-              break;
-            default:
-              errorMessage = `Action failed with status ${String(status)}${baseError ? `: ${baseError}` : ""}`;
-          }
-
-          failedCallback(errorMessage);
+          resultCallback(message.values);
         }
       } else if (isRosbridgeActionFeedbackMessage<TFeedback>(message)) {
         feedbackCallback?.(message.values);