Transferring MessagePort from worker thread does not work

[kylecarbs]

What version of Bun is running?

1.1.42+50eec0025

What platform is your computer?

Linux 6.6.61 aarch64 unknown

What steps can reproduce the bug?

// main.js
const { Worker } = require("node:worker_threads")
const worker = new Worker("./worker.js")
worker.on("message", (message) => {
    console.log(message)
})

// worker.js
const {parentPort} = require("worker_threads")
const { port1 } = new MessageChannel()
parentPort.postMessage({ port1 }, [port1])

Run main.js.

What is the expected behavior?

In NodeJS, output is as-expected.

$ node main.js
{
  port1: MessagePort [EventTarget] {
    active: true,
    refed: false,
    [Symbol(kEvents)]: SafeMap(2) [Map] {
      'newListener' => [Object],
      'removeListener' => [Object]
    },
    [Symbol(events.maxEventTargetListeners)]: 10,
    [Symbol(events.maxEventTargetListenersWarned)]: false,
    [Symbol(kNewListener)]: [Function (anonymous)],
    [Symbol(kRemoveListener)]: [Function (anonymous)],
    [Symbol(nodejs.internal.kCurrentlyReceivingPorts)]: undefined
  }
}

What do you see instead?

$ bun main.js
200 |   #onClose(e) {
201 |     this.#onExitPromise = e.code, this.emit("exit", e.code);
202 |   }
203 |   #onError(event) {
204 |     let error = event?.error;
205 |       error = new Error(event.message, { cause: event });
                    ^
error: 1 | const {parentPort} = require("worker_threads")
2 | const { port1 } = new MessageChannel()
3 | parentPort.postMessage({ port1 }, [port1])
               ^
TypeError: Unable to deserialize data.
      at /tmp/buntran/worker.js:3:12

 cause: {
  "isTrusted": true
}

      at #onError (node:worker_threads:205:15)

Bun v1.1.42 (Linux arm64)

Additional information

No response

[kylecarbs]

Error is coming from:

bun/src/bun.js/bindings/webcore/SerializedScriptValue.cpp

Lines 1718 to 1728 in 14b44ae

	if (obj->inherits<JSMessagePort>()) {
	auto index = m_transferredMessagePorts.find(obj);
	if (index != m_transferredMessagePorts.end()) {
	write(MessagePortReferenceTag);
	write(index->value);
	return true;
	}
	// MessagePort object could not be found in transferred message ports
	code = SerializationReturnCode::ValidationError;
	return true;
	}

[kylecarbs]

Transfering a MessagePort from main.js to worker.js works, just not the other way around.

[kylecarbs]

It also works when transfering a MessagePort over another MessagePort, just not when going through postMessage directly from the parentPort.