I try to use the upload widget in async mode to present a progress bar.
I add a bunch of form data within the upload event which works fine. Now I would like to validate the form data before uploading the file. If I do this in the upload event as well and set e.preventDefault() if validation fails, the list of selected files is cleared in the upload widget which doesn't make sense in this scenario as the customer is forced to correct the form data AND select the images again.
Is there a way to validate data before uploading a file without loosing the list of selected files?