Don't disable the button while bar has value

[takashi1kun]

Bug Report or Feature Request (mark with an x)

- [ ] bug report -> please search issues before submitting
- [ x] feature request

Desired functionality

It would be nice to have a option that when true doesn't disable the button when it has some value.

[AndreyBespamyatnov]

I think we could make something like that disabled: boolean | any | underfined
so based on the type we can or disable it or get it from function, and you can define your specific behavior as a function