$.widget() breaks class instances passed in widget prototype

[Victor Homyakov]

Updates of jQuery and jQuery UI broke the following widget code: ​http://jsfiddle.net/fyox1r56/2/ - works in jQuery 1.9.1 + jQuery 1.9.2 ​http://jsfiddle.net/fyox1r56/3/ - throws in jQuery 2.0.2 + jQuery 1.10.3

Now when widget prototype contains an object, it is cloned no matter when it's a plain object or an instance of some class with some code in its prototype chain.

This is because $.widget relies on isPlainObject functionality which was recently substantially changed in jQuery.

[Scott González]

This is not intended to work.

[Victor Homyakov]

Nowhere in the documentation for $.widget (​http://api.jqueryui.com/jQuery.widget/) was stated that not only widget's prototype, but also each and every of prototype's properties should be plain object (​http://api.jquery.com/Types/#PlainObject).

Also, nowhere is stated that prototype's properties not satisfying $.isPlainObject() are shallow cloned.

[Scott González]

This is just how prototypes work in JavaScript.