Set async flag in server module map only if module is actually async

Author: unstubbable

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

@@ -23,10 +23,7 @@ function nextFlightActionEntryLoader(this: any) {
 ${individualActions
   .map(([id, path, name]) => {
     // Re-export the same functions from the original module path as action IDs.
-    return `
-    const { ${name}: _${id} } = await import(${JSON.stringify(path)});
-    export { _${id} as "${id}" };
-`
+    return `export { ${name} as "${id}" } from ${JSON.stringify(path)}`
   })
   .join('\n')}
 `

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

@@ -55,7 +55,7 @@ const PLUGIN_NAME = 'FlightClientEntryPlugin'
 type Actions = {
   [actionId: string]: {
     workers: {
-      [name: string]: string | number
+      [name: string]: { moduleId: string | number; async: boolean }
     }
     // Record which layer the action is in (rsc or sc_action), in the specific entry.
     layer: {
@@ -79,15 +79,15 @@ 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 +879,11 @@ 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
@@ -965,7 +969,10 @@ 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

@@ -18,17 +18,12 @@ export function createServerModuleMap({
     {},
     {
       get: (_, id: string) => {
-        return {
-          id: serverActionsManifest[
+        const { moduleId, async } =
+          serverActionsManifest[
             process.env.NEXT_RUNTIME === 'edge' ? 'edge' : 'node'
-          ][id].workers[normalizeWorkerPageName(pageName)],
-          name: id,
-          chunks: [],
-          // Because of how next-flight-action-entry-loader creates the action
-          // entry modules, we know that these become async. So we set the flag
-          // accordingly.
-          async: true,
-        }
+          ][id].workers[normalizeWorkerPageName(pageName)]
+
+        return { id: moduleId, name: id, chunks: [], async }
       },
     }
   )