Cannot Use `triggerEvent` with "drop" to Trigger File Upload

[jherdman]

It seems like triggerEvent doesn't support the "drop" event. The corresponding change would require supporting the DataTransfer event API too.

[JimSchofield]

I've been able to mock a dataTransfer as far as sending information from a dragstart element to drop target:

async function dragMove(fromElement, toElement) {
  const context = {};

  await triggerEvent(fromElement, 'dragstart', {
    dataTransfer: {
      setData(someKey, value) {
        context[someKey] = value;
      },
    },
  });
  await triggerEvent(toElement, 'dragover', { dataTransfer: {} });
  await triggerEvent(toElement, 'drop', {
    dataTransfer: {
      getData(someKey) {
        return context[someKey];
      },
    },
  });
}

However, my components are not handling the 'drop' event emitted by triggerEvent. I'll see if I can find a minimal reproduction.

[JimSchofield]

I've submitted a PR with a dragMove helper. Maybe this would be of help @jherdman ?

#1139