I have created an annotation-based validation library called regula. There seems to be some amount of interest around the framework and the next thing I'd like to do is to support HTML5 validation. Originally I figured that I would check to see if the browser supported the HTML5 validation that has been specified and to either emulate or delegate to built-in regula equivalents. This is trivial for things like required, but once you start getting into the date-validation, it gets tricky (date widgets, localization, etc.). So I have a few options in front of me:

• Full HTML5 Shim along with widgets (for date stuff etc.): I feel like this is overkill and essentially reinventing the wheel since this is already covered by things like modernizr.
• Use HTML5 validation if available (either native, or provided by shim; otherwise ignore): What this means is that if HTML5 validation is available (natively or through a shim) I will use it, otherwise I will ignore it.

I'm leaning towards the latter since currently if someone wants to use HTML5 validation, they will most probably require a shim since not all browsers support HTML5.

Which option do you think is better?