Hello folks, I was thinking a little about how build flags that modify functionality are harmful for dependency resolution (pandoc and xmobar, I'm glaring at you), but authors will still use this feature because it's a lot easier than maintaining a bunch of separate packages for each different flag. It suddenly struck me, then, that what we actually needed was a mechanism not unlike what you see in traditional package managers, where a single Cabal file can specify multiple packages. pandoc.cabal might define 'pandoc' and 'pandoc-highlighting', and pandoc-highlighting can have different build dependencies, modules, etc. Module writers still need to arrange their APIs so that the extra functionality should be separable, but I don't see this as being too much of a problem. Mix-and-matching flags can be achieved by simply picking the extra virtual models as dependencies as necessary. What do you think? Cheers, Edward