Cabal and Tool Dependencies

1. How can I tell what tool dependencies a package has? For example, how can I tell from a .cabal package that Happy 1.14 or later, or Alex 2.0 is required for the package to build properly? I am making a simple tool that uses .cabal files to build programs and I would like to be able to say "This package requires Happy 1.14 to be installed" upon loading the .cabal file (before the user runs "./Setup.hs build"). 2. Is it possible to register binary (executable) packages? For example, I would like to "register" Happy 1.15 with Cabal, somehow, so that Cabal knows what version of Happy I have installed. This would eliminate the need for me to use --with-happy, etc. when configuring. Thanks, Brian