feat: validate config exports to improve error message (#1390)

packages/core/src/cli/config.ts

@@ -3,6 +3,7 @@ import { isAbsolute, join } from 'path';
 import {
   color,
   logger,
+  isObject,
   debounce,
   getNodeEnv,
   type RsbuildConfig,
@@ -125,6 +126,14 @@ export async function loadConfigByPath(configFile: string) {
       return result;
     }
 
+    if (!isObject(configExport)) {
+      throw new Error(
+        `Rsbuild config must be an object or a function that returns an object, get ${color.yellow(
+          configExport,
+        )}`,
+      );
+    }
+
     return configExport;
   } catch (err) {
     logger.error(`Failed to load file: ${color.dim(configFile)}`);