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Unfortunately this doesn't implement the events properly because it will pass through the USBConnectionEvent objects instead of translating them to their Web Serial API equivalents. As you guessed on #20 I did start working on a patch to implement connection events but unfortunately it's non-trivial to get right because EventTarget doesn't support specifying a custom "get the parent" algorithm. That is tracked by whatwg/dom#583 but we can probably work around it by implementing our own Event interface and dispatching routine.

Alright, I feared it would not be as easy as I thought. I mean - technically it seems to be working, at least for my use case the disconnect handler is triggered. But I will leave it now up to you to finish your proper solution.

Hey @reillyeon - just wanted to bump this issue since I am now running into the same issue with a different project and was wondering if there is any chance you made any progress with this?

I haven't had a chance to look at this. As a workaround your code can add its own listeners for the connect and disconnect events on navigator.usb. You can use the SerialPort constructor to turn a USBDevice instance into a SerialPort instance. It just really shouldn't be fired through the polyfill unless we can turn it to the right kind of event on the SerialPort interface.

Alright, I will give that a try, thank you.