Make esm default interpolation work with jest mock (#36877)

fixes https://github.com/vercel/next.js/issues/36794

packages/next/taskfile-swc.js

@@ -118,6 +118,7 @@ module.exports = function (task) {
         if (interopClientDefaultExport) {
           output.code += `
 if (typeof exports.default === 'function' || (typeof exports.default === 'object' && exports.default !== null)) {
+  Object.defineProperty(exports.default, '__esModule', { value: true });
   Object.assign(exports.default, exports);
   module.exports = exports.default;
 }

test/unit/esm-interpolate/esm-interpolate.test.tsx

@@ -0,0 +1,14 @@
+import React from 'react'
+import { renderToString } from 'react-dom/server'
+import * as nextRouter from 'next/router'
+
+import { Foo } from './fixture'
+
+// @ts-expect-error
+jest.spyOn(nextRouter, 'useRouter').mockReturnValue({
+  pathname: 'Hello',
+})
+
+test('mock the interpolated modules should work', () => {
+  expect(renderToString(<Foo />)).toBe(`<div>Hello</div>`)
+})

test/unit/esm-interpolate/fixture.tsx

@@ -0,0 +1,8 @@
+import React from 'react'
+import { useRouter } from 'next/router'
+
+export const Foo = () => {
+  const router = useRouter()
+
+  return <div>{router.pathname}</div>
+}