Avoid server action endpoint function indirection

packages/next/src/build/webpack/loaders/next-flight-action-entry-loader.ts

@@ -20,29 +20,12 @@ function nextFlightActionEntryLoader(this: any) {
     .flat()
 
   return `
-const actions = {
 ${individualActions
   .map(([id, path, name]) => {
-    return `'${id}': () => import(/* webpackMode: "eager" */ ${JSON.stringify(
-      path
-    )}).then(mod => mod[${JSON.stringify(name)}]),`
+    // Re-export the same functions from the original module path as action IDs.
+    return `export { ${name} as "${id}" } from ${JSON.stringify(path)}`
   })
   .join('\n')}
-}
-
-async function endpoint(id, ...args) {
-  const action = await actions[id]()
-  return action.apply(null, args)
-}
-
-// Using CJS to avoid this to be tree-shaken away due to unused exports.
-module.exports = {
-${individualActions
-  .map(([id]) => {
-    return `  '${id}': endpoint.bind(null, '${id}'),`
-  })
-  .join('\n')}
-}
 `
 }
 

packages/next/src/build/webpack/plugins/flight-client-entry-plugin.ts

@@ -55,7 +55,11 @@ const PLUGIN_NAME = 'FlightClientEntryPlugin'
 type Actions = {
   [actionId: string]: {
     workers: {
-      [name: string]: string | number
+      [name: string]:
+        | { moduleId: string | number; async: boolean }
+        // TODO: This is legacy for Turbopack, and needs to be changed to the
+        // object above.
+        | string
     }
     // Record which layer the action is in (rsc or sc_action), in the specific entry.
     layer: {
@@ -79,15 +83,15 @@ const pluginState = getProxiedPluginState({
   actionModServerId: {} as Record<
     string,
     {
-      server?: string | number
-      client?: string | number
+      server?: { moduleId: string | number; async: boolean }
+      client?: { moduleId: string | number; async: boolean }
     }
   >,
   actionModEdgeServerId: {} as Record<
     string,
     {
-      server?: string | number
-      client?: string | number
+      server?: { moduleId: string | number; async: boolean }
+      client?: { moduleId: string | number; async: boolean }
     }
   >,
 
@@ -879,7 +883,11 @@ export class FlightClientEntryPlugin {
             layer: {},
           }
         }
-        currentCompilerServerActions[id].workers[bundlePath] = ''
+        currentCompilerServerActions[id].workers[bundlePath] = {
+          moduleId: '', // TODO: What's the meaning of this?
+          async: false,
+        }
+
         currentCompilerServerActions[id].layer[bundlePath] = fromClient
           ? WEBPACK_LAYERS.actionBrowser
           : WEBPACK_LAYERS.reactServerComponents
@@ -928,6 +936,13 @@ export class FlightClientEntryPlugin {
           }
 
           compilation.hooks.succeedEntry.call(dependency, options, module)
+
+          compilation.moduleGraph
+            .getExportsInfo(module)
+            .setUsedInUnknownWay(
+              this.isEdgeServer ? EDGE_RUNTIME_WEBPACK : DEFAULT_RUNTIME_WEBPACK
+            )
+
           return resolve(module)
         }
       )
@@ -958,7 +973,10 @@ export class FlightClientEntryPlugin {
         if (!mapping[chunkGroup.name]) {
           mapping[chunkGroup.name] = {}
         }
-        mapping[chunkGroup.name][fromClient ? 'client' : 'server'] = modId
+        mapping[chunkGroup.name][fromClient ? 'client' : 'server'] = {
+          moduleId: modId,
+          async: compilation.moduleGraph.isAsync(mod),
+        }
       }
     })
 

packages/next/src/server/app-render/action-utils.ts

@@ -18,13 +18,18 @@ export function createServerModuleMap({
     {},
     {
       get: (_, id: string) => {
-        return {
-          id: serverActionsManifest[
+        const workerEntry =
+          serverActionsManifest[
             process.env.NEXT_RUNTIME === 'edge' ? 'edge' : 'node'
-          ][id].workers[normalizeWorkerPageName(pageName)],
-          name: id,
-          chunks: [],
+          ][id].workers[normalizeWorkerPageName(pageName)]
+
+        if (typeof workerEntry === 'string') {
+          return { id: workerEntry, name: id, chunks: [] }
         }
+
+        const { moduleId, async } = workerEntry
+
+        return { id: moduleId, name: id, chunks: [], async }
       },
     }
   )

test/e2e/app-dir/actions/app-action.test.ts

@@ -828,6 +828,24 @@ describe('app-dir action handling', () => {
     ).toBe(true)
   })
 
+  // we don't have access to runtime logs on deploy
+  if (!isNextDeploy) {
+    it('should keep action instances identical', async () => {
+      const logs: string[] = []
+      next.on('stdout', (log) => {
+        logs.push(log)
+      })
+
+      const browser = await next.browser('/identity')
+
+      await browser.elementByCss('button').click()
+
+      await retry(() => {
+        expect(logs.join('')).toContain('result: true')
+      })
+    })
+  }
+
   it.each(['node', 'edge'])(
     'should forward action request to a worker that contains the action handler (%s)',
     async (runtime) => {

test/e2e/app-dir/actions/app/identity/client.js

@@ -0,0 +1,13 @@
+'use client'
+
+export function Client({ foo, b }) {
+  return (
+    <button
+      onClick={() => {
+        foo(b)
+      }}
+    >
+      Trigger
+    </button>
+  )
+}

test/e2e/app-dir/actions/app/identity/page.js

@@ -0,0 +1,14 @@
+import { Client } from './client'
+
+export default async function Page() {
+  async function b() {
+    'use server'
+  }
+
+  async function foo(a) {
+    'use server'
+    console.log('result:', a === b)
+  }
+
+  return <Client foo={foo} b={b} />
+}