zendframework/zf2 — pull request #4165 by zburnham (2013-04-02 02:36:10+00:00)
Title: Validate empty with context

Trying this again, I messed up a rebase.

Currently there is no way for Zend\InputFilter to determine the validity of an empty field based on context; for example, an empty field might be valid if another field is 'Y', but not valid if that other field is 'N'. This adds a continueIfEmpty flag to the Input definition, via a separate interface.