Am I right that the way to do this now is create your own preprocessor run on files havirg your extionsion? What about naming the source files eg Module.hs.cpp.di.gc.chs ? This would mean first run c2hs, then greencard thin DrIft then cpp and put the results in Module.hs.cpp.di.gc.chs 1) Module.hs.cpp.di.gc 2)` Module.hs.cpp Module.hs pro : you see immediately which preprocessors are to be invoked you don't need write your own preprocessor handler.. con : There are to much possibilities to use doesFileExist? so the way to get the source file is using getDirectoryContents and filter by regex \.hs.* \.lhs.* matches and take longest filename (So that 1) will be perefered over 2) You need a customizable editor to set filetype by regular expression rather by (.gc .hs .lhs .chs ..) What do you think, would this be an enhancement? I'd like to implement this and provide a darcs patch to cabal 1.1.7 Any ideas/ comments on this? Marc