Several libraries (notably Pandoc and Gtk2hs) have very complex Setup.hs scripts, which import several external libraries. In my experience, these imports are very fragile, because Cabal does not enforce package visibility in Setup.hs. For example, a Setup.hs that imports Control.Monad.Trans will break if "monads-tf" is installed, and one that imports System.FilePath will break if "system-filepath" is installed. My typical solution when this happens is to manually tweak the GHC package database before installing, but this is annoying and does not help other users. Based on a ticket in Cabal's Trac < http://hackage.haskell.org/trac/hackage/ticket/326 >, custom Setup.hs scripts are discouraged by the Cabal developers. I assume this means there will not be much development effort put towards an integrated solution (such as using -hide-all-packages and build-depends: when compiling Setup.hs). A possible solution is to ask developers with complex Setup.hs requirements to use the PackageImports language extension when importing external libraries. However, this places a burden on such developers, and I don't know if it's portable to non-GHC compilers. It would also need an analysis of currently published Hackage packages to see which have such scripts. Any ideas/comments? Has anyone by chance found a good solution to this?