[Flight] Support Async Modules in Server References (#31313)

This is required to support for example top level await in a "use
server" module or dependency of a "use server".

packages/react-server-dom-webpack/src/client/ReactFlightClientConfigBundlerWebpack.js

@@ -86,6 +86,13 @@ export function resolveClientReference<T>(
  }
  name = metadata[NAME];
  }
+ // Note that resolvedModuleData.async may be set if this is an Async Module.
+ // For Client References we don't actually care because what matters is whether
+ // the consumer expects an unwrapped async module or just a raw Promise so it
+ // has to already know which one it wants.
+ // We could error if this is an Async Import but it's not an Async Module.
+ // However, we also support plain CJS exporting a top level Promise which is not
+ // an Async Module according to the bundle graph but is effectively the same.
  if (isAsyncImport(metadata)) {
  return [
  resolvedModuleData.id,
@@ -128,7 +135,19 @@ export function resolveServerReference<T>(
  );
  }
  }
- // TODO: This needs to return async: true if it's an async module.
+ if (resolvedModuleData.async) {
+ // If the module is marked as async in a Client Reference, we don't actually care.
+ // What matters is whether the consumer wants to unwrap it or not.
+ // For Server References, it is different because the consumer is completely internal
+ // to the bundler. So instead of passing it to each reference we can mark it in the
+ // manifest.
+ return [
+ resolvedModuleData.id,
+ resolvedModuleData.chunks,
+ name,
+ 1 /* async */,
+ ];
+ }
  return [resolvedModuleData.id, resolvedModuleData.chunks, name];
 }