Autocomplete plugin disables custom 'window.onbeforeunload' listener

The fix for jQuery UI bug #7790 introduced a new issue. See ticket:7790#comment:5. If I create my own window.onbeforeunload listener, autocomplete disables it.

$(window).bind('beforeunload', ...) does not support binding multiple listeners. So it's up to autocomplete to check for an existing listener, and delegate to it after doing its own work.

This is a rather insidious issue because upgrading to jQuery UI 1.8.17 will break previously-functional behavior in the user's application. It has the potential to cause data loss because a common use of 'beforeunload' is to warn the user of unsaved changes. Autocomplete binds this listener with no option to disable or restore the previous behavior.

A very hacky workaround is to attempt to reset the custom listener whenever autocomplete is used:

var autocomplete = $.fn.autocomplete;	// original fn
$.fn.autocomplete = function() {	// intercept calls to $().autocomplete()
	var result = autocomplete.apply(this, arguments);	// delegate
	window.onbeforeunload = myCustomBeforeunloadListener;	// reset
	return result;
};

The issue is present as of 1.8.21