Typeahead: allow selection veto

[pkozlowski-opensource]

In some more advanced use-cases a typeahead might display more options than are supposed to be selected by a user. An example of this can be seen on https://www.kayak.com/flights where in addition to flight proposal there is the "Sign up to access recent searches anywhere". It looks like a "normal" option (is displayed in a dropdown, can be iterated over with keyboard etc.) except that it can't be selected and shouldn't result in model binding.

We could easily cover this use-case by giving people ability to veto selection in the selectItem callback (ex. by interpreting false as a return value or changing event we pass to the selectItem function).

[pkozlowski-opensource]

This is similar to typeahead-should-select from http://angular-ui.github.io/bootstrap/#/typeahead. At the same time I don't see why we should be separating typeahead-on-select and typeahead-should-select as we can combine them into one.

My proposal: check the return value from the selectItem callback (if one was defined). If the return value is equal to false then don't write back to the model value.

[pkozlowski-opensource]

Bah, we can't do this... I'm not thinking straight - we are just emitting through EventEmitter so I don't think we can expect a return value. What we would have to do is to provide an event object and have a preventDefault() method on this event object.