[whatwg] [wf2] Filtering datalist with pattern

[Matthew Raymond]

Henri Sivonen wrote:
> The WF2 spec does not say anything about filtering autocomplete lists  
> on pattern and Opera 9 does not do it. However, autocomplete entries  
> that would fail form validation are not particularly useful.
> 
> I suggest saying that potential autocomplete items (whether supplied  
> by the UA itself or read from a datalist) should be tested against  
> the datatype and the pattern of the form field being filled and  
> should only be shown if they match both the datatype and the pattern.

   This assumes that the inclusion of such items is unintentional. What
if you wanted the user to be able to select from a fixed set of values
that fall outside of the pattern in addition to those that fit the
pattern? Is the proper way to handle this to force web authors to write
these values into the pattern? This could be rather troublesome if you
have a significant set of nonconforming datalist values.