fix: prevent client proxy from being treated as a thenable

[darshkpatel]

Why

River's client proxy uses _createRecursiveProxy which returns a callable proxy for any string property access, including .then. This causes a bug when a River client is resolved from a Promise:

// This throws "invalid river call, ensure the service and procedure you are calling exists"
const client = await spawnWorker().then(handle => handle.client);

JavaScript's Promise resolution procedure checks typeof value.then === 'function' on the resolved value. Since the proxy intercepts .then and returns a callable proxy, the runtime treats the client as a thenable and invokes .then(resolve, reject). This triggers the apply trap with path ["then"], which fails the serviceName && procName && procMethod check.

This was discovered in repl-it-web#67471 where the scribe service spawns a worker thread and returns the River client from a .then() callback.

What changed

router/client.ts: Return undefined for .then access in the recursive proxy's get trap:

get(_obj, key) {
  if (typeof key !== 'string') return undefined;
  if (key === 'then') return undefined; // prevent thenable detection
  return _createRecursiveProxy(callback, [...path, key]);
}

__tests__/typescript-stress.test.ts: Two tests confirming:

• client.then is undefined
• A client resolved from Promise.resolve().then(() => client) is the same object (not re-wrapped as a thenable)

Versioning

• Breaking protocol change
• Breaking ts/js API change

~ written by Zerg 👾

[jackyzha0]

lol nice

[jackyzha0]

dont forget to bump the package version