fix: arrow function export in rsc client component (vercel#34105)

The `export default xxx` statement is slightly different from estree when exporting an arrow function instead of identifier in swc.
We also need to capture arrow exports.

packages/next/build/webpack/loaders/next-flight-client-loader.ts

@@ -62,6 +62,7 @@ async function parseExportNamesInto(
     switch (node.type) {
       // TODO: support export * from module path
       // case 'ExportAllDeclaration':
+      case 'ExportDefaultExpression':
       case 'ExportDefaultDeclaration':
         names.push('default')
         continue

test/integration/react-streaming-and-server-components/app/components/client-default-export-arrow.client.js

@@ -0,0 +1 @@
+export default () => 'client-default-export-arrow'

test/integration/react-streaming-and-server-components/app/pages/client-exports-all.server.js

@@ -1,6 +1,7 @@
 import * as all from '../components/client-exports-all'
 import * as allClient from '../components/client-exports-all.client'
 
+// TODO: support export all declaration
 export default function Page() {
   const { a, b, c, d, e } = all
   const { a: ac, b: bc, c: cc, d: dc, e: ec } = allClient

test/integration/react-streaming-and-server-components/app/pages/client-exports.server.js

@@ -1,13 +1,19 @@
 import { a, b, c, d, e } from '../components/client-exports'
+import DefaultArrow from '../components/client-default-export-arrow.client'
 
 export default function Page() {
   return (
     <div>
-      {a}
-      {b}
-      {c}
-      {d}
-      {e[0]}
+      <div id="named-exports">
+        {a}
+        {b}
+        {c}
+        {d}
+        {e[0]}
+      </div>
+      <div id="default-exports-arrow">
+        <DefaultArrow />
+      </div>
     </div>
   )
 }

test/integration/react-streaming-and-server-components/test/rsc.js

@@ -66,10 +66,21 @@ export default function (context) {
       '/client-exports'
     )
     const $clientExports = cheerio.load(clientExportsHTML)
-    expect($clientExports('div[hidden] > div').text()).toBe('abcde')
+    expect($clientExports('div[hidden] > div > #named-exports').text()).toBe(
+      'abcde'
+    )
+    expect(
+      $clientExports('div[hidden] > div > #default-exports-arrow').text()
+    ).toBe('client-default-export-arrow')
 
     const browser = await webdriver(context.appPort, '/client-exports')
-    const text = await browser.waitForElementByCss('#__next').text()
-    expect(text).toBe('abcde')
+    const textNamedExports = await browser
+      .waitForElementByCss('#named-exports')
+      .text()
+    const textDefaultExportsArrow = await browser
+      .waitForElementByCss('#default-exports-arrow')
+      .text()
+    expect(textNamedExports).toBe('abcde')
+    expect(textDefaultExportsArrow).toBe('client-default-export-arrow')
   })
 }