Make isRspack strict and align tests

Author: justin808

client/__tests__/webpack/bundlerUtils.spec.js

@@ -80,12 +80,12 @@ describe('bundlerUtils', () => {
       expect(utils.isRspack()).toBe(true);
     });
 
-    it('returns false when assets_bundler is webpack', () => {
+    it('throws when assets_bundler is webpack', () => {
       mockConfig.assets_bundler = 'webpack';
       jest.doMock('shakapacker', () => ({ config: mockConfig }));
       const utils = require('../../../config/webpack/bundlerUtils');
 
-      expect(utils.isRspack()).toBe(false);
+      expect(() => utils.isRspack()).toThrow('configured for Rspack only');
     });
   });
 

config/webpack/bundlerUtils.js

@@ -37,6 +37,16 @@ const getBundler = () => {
   return _cachedBundler;
 };
 
+/**
+ * Validates rspack-only mode and returns true.
+ *
+ * @returns {boolean} Always true after validation
+ */
+const isRspack = () => {
+  ensureRspack();
+  return true;
+};
+
 /**
  * Gets the CSS extraction plugin for Rspack.
  *
@@ -46,5 +56,6 @@ const getCssExtractPlugin = () => getBundler().CssExtractRspackPlugin;
 
 module.exports = {
   getBundler,
+  isRspack,
   getCssExtractPlugin,
 };