Fix named export missing from client components (#34974)

Closes #33538.

## Bug

- [x] Related issues linked using `fixes #number`
- [x] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`

## Feature

- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have helpful link attached, see `contributing.md`

## Documentation / Examples

- [ ] Make sure the linting passes by running `yarn lint`

packages/next/build/webpack-config.ts

@@ -1598,7 +1598,12 @@ export default async function getBaseWebpackConfig(
     if (!webpack5Config.optimization) {
       webpack5Config.optimization = {}
     }
-    webpack5Config.optimization.providedExports = false
+
+    // For Server Components, it's necessary to have provided exports collected
+    // to generate the correct flight manifest.
+    if (!hasServerComponents) {
+      webpack5Config.optimization.providedExports = false
+    }
     webpack5Config.optimization.usedExports = false
   }
 

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

@@ -75,6 +75,11 @@ async function parseExportNamesInto(
           }
         }
         continue
+      case 'ExportDeclaration':
+        if (node.declaration?.identifier) {
+          addExportNames(names, node.declaration.identifier)
+        }
+        continue
       default:
         break
     }

packages/next/build/webpack/plugins/flight-manifest-plugin.ts

@@ -82,12 +82,15 @@ export class FlightManifestPlugin {
         const moduleExports: any = json[resource] || {}
 
         const exportsInfo = compilation.moduleGraph.getExportsInfo(mod)
-        const providedExports = exportsInfo.getProvidedExports()
         const moduleExportedKeys = ['', '*'].concat(
-          // TODO: improve exports detection
-          providedExports === true || providedExports == null
-            ? 'default'
-            : providedExports
+          [...exportsInfo.exports]
+            .map((exportInfo) => {
+              if (exportInfo.provided) {
+                return exportInfo.name
+              }
+              return null
+            })
+            .filter(Boolean)
         )
 
         moduleExportedKeys.forEach((name) => {

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

@@ -0,0 +1,3 @@
+export function Named() {
+  return 'named export: named.client'
+}

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

@@ -1,4 +1,6 @@
 import Foo from '../components/foo.client'
+import { Named } from '../components/named.client'
+
 import Link from 'next/link'
 
 const envVar = process.env.ENV_VAR_TEST
@@ -11,6 +13,9 @@ export default function Index({ header, router }) {
       <div>{'path:' + router.pathname}</div>
       <div>{'env:' + envVar}</div>
       <div>{'header:' + header}</div>
+      <div>
+        <Named />
+      </div>
       <div>
         <Foo />
       </div>

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

@@ -28,6 +28,7 @@ export default function (context, { runtime, env }) {
     expect(homeHTML).toContain('header:test-util')
     expect(homeHTML).toContain('path:/')
     expect(homeHTML).toContain('foo.client')
+    expect(homeHTML).toContain('named.client')
   })
 
   it('should reuse the inline flight response without sending extra requests', async () => {