Bug: MessageChannel in Scheduler prevents Jest test from exiting about react

[s100]

Thank you very much for the workaround! In practice I found that simply unrefing the port immediately on creation did not do the trick, because as soon as scheduler calls channel.port1.onmessage = performWorkUntilDeadline the port becomes reffed again. I had to do something more complex:

const MessageChannelOriginal = global.MessageChannel
global.MessageChannel = class {
  constructor () {
    const channel = new MessageChannelOriginal()
    this.port1 = new Proxy(channel.port1, {
      set (port1, prop, value) {
        const result = Reflect.set(port1, prop, value)
        if (prop === 'onmessage') {
          port1.unref()
        }
        return result
      }
    })
    this.port2 = channel.port2
  }
}

Alternatively, as I happen to be using Mocha, I found that the --exit flag also worked.

[victor-homyakov]

@victor-homyakov Are you aware of any kind of workaround for this?

The workaround is to use patched MessageChannel in JSDom, something like

const MessageChannelOriginal = require('node:worker_threads').MessageChannel;
class MessageChannel {
    constructor() {
        const channel = new MessageChannelOriginal();
        // Allow the thread to exit if this is the only active handle in the event system
        if (channel.port1.unref) {
            channel.port1.unref();
        }
        this.channel = channel;
    }
    get port1() {
        return this.channel.port1;
    }
    // ...
}
window.MessageChannel = MessageChannel;

[s100]

I'm seeing the same issue during some experiments with Mocha testing. The suggested fix works for me. I will produce a minimal repro if that's considered desirable.

@victor-homyakov Are you aware of any kind of workaround for this?

[github-actions]

This issue has been automatically marked as stale. If this issue is still affecting you, please leave any comment (for example, "bump"), and we'll keep it open. We are sorry that we haven't been able to prioritize it yet. If you have any new additional information, please include it with your comment!

[s100]

Bump, this is still an issue for us.