fix(exports): support default-only module shape in ESM wrapper

exports/index.mjs

@@ -1,8 +1,10 @@
 // ES modules wrapper
-import { createRequire } from 'node:module';
+import pluginModule from '../dist/index.js';
 
-const require = createRequire(import.meta.url);
-const { ReactRefreshRspackPlugin } = require('../dist/index.js');
+const ReactRefreshRspackPlugin =
+  pluginModule?.ReactRefreshRspackPlugin ??
+  pluginModule?.default ??
+  pluginModule;
 
 // default export will be deprecated in next major version
 export default ReactRefreshRspackPlugin;

test/exports-default-fallback.spec.mts

@@ -0,0 +1,31 @@
+import { mkdtempSync, readFileSync, rmSync, writeFileSync } from 'node:fs';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+import { pathToFileURL } from 'node:url';
+
+test('esm wrapper supports default-only dist export shape', async () => {
+  const tempDir = mkdtempSync(join(tmpdir(), 'react-refresh-export-wrapper-'));
+  try {
+    const wrapperSource = readFileSync('exports/index.mjs', 'utf8');
+    const wrapperPath = join(tempDir, 'index.mjs');
+    const fixturePath = join(tempDir, 'dist-fixture.mjs');
+    const fixtureClassName = 'MockReactRefreshRspackPlugin';
+
+    writeFileSync(
+      fixturePath,
+      `export default class ${fixtureClassName} {\n  constructor() {\n    this.options = { reactRefreshLoader: true };\n  }\n}\n`,
+    );
+    writeFileSync(
+      wrapperPath,
+      wrapperSource.replace('../dist/index.js', './dist-fixture.mjs'),
+    );
+
+    const mod = await import(pathToFileURL(wrapperPath).href);
+    const instance = new mod.ReactRefreshRspackPlugin();
+
+    expect(instance.options.reactRefreshLoader).toBeTruthy();
+    expect(mod.default).toBe(mod.ReactRefreshRspackPlugin);
+  } finally {
+    rmSync(tempDir, { recursive: true, force: true });
+  }
+});