Prevent exports of nextFlightActionEntryLoader from getting DCE'd

Author: unstubbable

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

@@ -20,18 +20,13 @@ function nextFlightActionEntryLoader(this: any) {
     .flat()
 
   return `
-${individualActions
-  .map(([_, path]) => {
-    // This import ensures that the module is always bundled even if there's no
-    // explicit import in the codebase, to avoid the action being DCE'd.
-    return `import(/* webpackMode: "eager" */ ${JSON.stringify(path)});`
-  })
-  .join('\n')}
-
 ${individualActions
   .map(([id, path, name]) => {
     // Re-export the same functions from the original module path as action IDs.
-    return `export { ${name} as "${id}" } from ${JSON.stringify(path)}`
+    return `
+    const { ${name}: _${id} } = await import(${JSON.stringify(path)});
+    export { _${id} as "${id}" };
+`
   })
   .join('\n')}
 `

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

@@ -928,6 +928,13 @@ 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)
         }
       )

packages/next/src/compiled/react-server-dom-webpack/cjs/react-server-dom-webpack-client.edge.production.js

@@ -48,7 +48,9 @@ function resolveServerReference(bundlerConfig, id) {
           '" in the React Server Manifest. This is probably a bug in the React Server Components bundler.'
       );
   }
-  return [resolvedModuleData.id, resolvedModuleData.chunks, name];
+  return resolvedModuleData.async
+    ? [resolvedModuleData.id, resolvedModuleData.chunks, name, 1]
+    : [resolvedModuleData.id, resolvedModuleData.chunks, name];
 }
 var chunkCache = new Map();
 function requireAsyncModule(id) {

packages/next/src/compiled/react-server-dom-webpack/cjs/react-server-dom-webpack-server.edge.production.js

@@ -1947,7 +1947,9 @@ function resolveServerReference(bundlerConfig, id) {
           '" in the React Server Manifest. This is probably a bug in the React Server Components bundler.'
       );
   }
-  return [resolvedModuleData.id, resolvedModuleData.chunks, name];
+  return resolvedModuleData.async
+    ? [resolvedModuleData.id, resolvedModuleData.chunks, name, 1]
+    : [resolvedModuleData.id, resolvedModuleData.chunks, name];
 }
 var chunkCache = new Map();
 function requireAsyncModule(id) {

packages/next/src/compiled/react-server-dom-webpack/cjs/react-server-dom-webpack-server.node.development.js

@@ -2472,7 +2472,9 @@
               '" in the React Server Manifest. This is probably a bug in the React Server Components bundler.'
           );
       }
-      return [resolvedModuleData.id, resolvedModuleData.chunks, name];
+      return resolvedModuleData.async
+        ? [resolvedModuleData.id, resolvedModuleData.chunks, name, 1]
+        : [resolvedModuleData.id, resolvedModuleData.chunks, name];
     }
     function requireAsyncModule(id) {
       var promise = globalThis.__next_require__(id);

packages/next/src/compiled/react-server-dom-webpack/cjs/react-server-dom-webpack-server.node.production.js

@@ -1983,7 +1983,9 @@ function resolveServerReference(bundlerConfig, id) {
           '" in the React Server Manifest. This is probably a bug in the React Server Components bundler.'
       );
   }
-  return [resolvedModuleData.id, resolvedModuleData.chunks, name];
+  return resolvedModuleData.async
+    ? [resolvedModuleData.id, resolvedModuleData.chunks, name, 1]
+    : [resolvedModuleData.id, resolvedModuleData.chunks, name];
 }
 var chunkCache = new Map();
 function requireAsyncModule(id) {

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

@@ -24,6 +24,10 @@ export function createServerModuleMap({
           ][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,
         }
       },
     }