fix(Stop and Error Node): Show error message when error type is an object (#17898)

packages/nodes-base/nodes/StopAndError/utils.ts

@@ -0,0 +1,45 @@
+import type { JsonObject } from 'n8n-workflow';
+import { jsonParse } from 'n8n-workflow';
+
+export interface ErrorHandlerResult {
+	message: string;
+	options?: {
+		description?: string;
+		type?: string;
+		level: 'error';
+		metadata?: JsonObject;
+	};
+}
+
+function isString(value: unknown): value is string {
+	return typeof value === 'string' && value.length > 0;
+}
+
+export function createErrorFromParameters(
+	errorType: 'errorMessage' | 'errorObject',
+	errorParameter: string,
+): ErrorHandlerResult {
+	if (errorType === 'errorMessage') {
+		return {
+			message: errorParameter,
+		};
+	} else {
+		const errorObject = jsonParse<JsonObject>(errorParameter);
+
+		const errorMessage =
+			(isString(errorObject.message) ? errorObject.message : '') ||
+			(isString(errorObject.description) ? errorObject.description : '') ||
+			(isString(errorObject.error) ? errorObject.error : '') ||
+			`Error: ${JSON.stringify(errorObject)}`;
+
+		return {
+			message: errorMessage,
+			options: {
+				description: isString(errorObject.description) ? errorObject.description : undefined,
+				type: isString(errorObject.type) ? errorObject.type : undefined,
+				level: 'error',
+				metadata: errorObject,
+			},
+		};
+	}
+}