test(v4): ensure proper error handling for invalid config

test/error-handling/index.test.ts

@@ -0,0 +1,33 @@
+import { dirname } from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { expect, test } from '@playwright/test';
+import { createRsbuild } from '@rsbuild/core';
+import { pluginTailwindCSS } from '../../src';
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+
+test('should fail with clear error when config file is missing', async () => {
+  const rsbuild = await createRsbuild({
+    cwd: __dirname,
+    rsbuildConfig: {
+      plugins: [
+        pluginTailwindCSS({
+          config: './does-not-exist.js',
+        }),
+      ],
+    },
+  });
+
+  // We expect the build to fail
+  try {
+    await rsbuild.build();
+    throw new Error('Build was expected to fail, but it succeeded.');
+  } catch (err: unknown) {
+    const error = err as Error;
+    // Check for error message
+    // Rsbuild might wrap the error, so we check for generic failure or specific message
+    expect(error.message).toMatch(
+      /Rspack build failed|Cannot find module|ENOENT|no such file/i,
+    );
+  }
+});

test/error-handling/src/index.js

@@ -0,0 +1 @@
+console.log('Error handling test');