fix(nextjs-mf): await async factories and return wrapper factory in server onLoad

[shashank-u03]

Description

Remote containers in @module-federation/runtime expose async module factories (RemoteEntryExports.get returns () => Promise<Module>).

During the webpack build/SSR path, runtime-core loads remotes with loadFactory: false and from: 'build' (see packages/webpack-bundler-runtime/src/remotes.ts), passing the unexecuted factory to nextjs-mf's onLoad hook as exposeModuleFactory.

On the server, onLoad synchronously invoked that factory and Proxy-wrapped the return value for chunk-usage tracking. When the factory is async, the sync invocation returned a raw Promise. Proxy-wrapping that Promise caused webpack's async module runtime to fail when calling .then():

TypeError: Method Promise.prototype.then called on incompatible receiver [object Promise]

runtime-core catches this in loadRemote and routes it to errorLoadRemote with lifecycle: 'onLoad' and from: 'build'.

Fix:

1. Await Promise results from moduleOrFactory() before applying the existing Proxy wrapper on the server.
2. When the resolved export is a namespace object and the input was exposeModuleFactory, return a wrapper factory so loadRemote can adopt the proxied result (runtime-core only uses onLoad's return when it is a function - see packages/runtime-core/src/remote/index.ts).

runtime-core already handles async factories in module.wraperFactory; this aligns nextjs-mf onLoad with that behavior.

Tests added in runtimePlugin.test.ts:

• Async factory is awaited before proxy-wrapping on the server
• Wrapper factory is returned for async namespace exports on the server
• Promise.prototype.then is not broken after the fix
• Sync exposeModuleFactory still works
• Rejected async factories propagate correctly
• Client path (window present) still returns args unchanged
  Note on async onLoad: loadRemote always awaits onLoad.emit() and AsyncHook.emit wraps listener returns with Promise.resolve(). The client branch still returns args unchanged; only the server branch gained internal await logic.

Related Issue

#2218

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Checklist

• I have added tests to cover my changes.
• All new and existing tests passed.
• I have updated the documentation.

[changeset-bot]

🦋 Changeset detected

Latest commit: cc62ed0

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@module-federation/nextjs-mf	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR