These functions were temporarily ripped out of Shiny and moved
to the htmltools package. We've discovered that it's safe to
keep including them in shiny; as long as the functions in shiny
and the functions in htmltools are identical, the user won't
receive a conflict warning.
- validateInput renamed to validate
- validateCondition renamed to need
- Removed ability to provide "bare" conditions. It is
still possible to fail validation silently by passing
FALSE as the second argument to need()
- Rather than using a two-element list to convey results,
use a single result protocol; NULL is success, FALSE is
silent failure, string is failure with message
- Tweak "missing input" semantics, add tests
