feat: add css files to server bundle for optimizeCss feature to work

packages/open-next/src/build/copyTracedFiles.ts

@@ -2,6 +2,7 @@ import url from "node:url";
 
 import {
   copyFileSync,
+  cpSync,
   existsSync,
   mkdirSync,
   readFileSync,
@@ -360,11 +361,25 @@ File ${serverPath} does not exist
       .forEach((file) => copyStaticFile(`server/${file}`));
   }
 
+  const manifests = getManifests(standaloneNextDir);
+
+  const { optimizeCss } = manifests.config.experimental;
+
+  // Copy .next/static/css from standalone to output dir
+  // needed for optimizeCss feature to work
+  if (optimizeCss) {
+    cpSync(
+      path.join(standaloneNextDir, "static", "css"),
+      path.join(outputNextDir, "static", "css"),
+      { recursive: true },
+    );
+  }
+
   logger.debug("copyTracedFiles:", Date.now() - tsStart, "ms");
 
   return {
     tracedFiles,
     nodePackages,
-    manifests: getManifests(standaloneNextDir),
+    manifests,
   };
 }

packages/open-next/src/types/next-types.ts

@@ -82,6 +82,7 @@ export interface NextConfig {
   experimental: {
     serverActions?: boolean;
     appDir?: boolean;
+    optimizeCss?: boolean;
   };
   images: ImageConfig;
   poweredByHeader?: boolean;