"Conal Elliott"
Marc points out that the expressiveness of the Cabal language is insufficient for some packages, and a DSEL would be more expressive. I have the same problem and still have to resort to makefiles to augment my .cabal files.
The original design of Cabal was more like Marc suggests. There was only the Setup file and no .cabal file, and my hope was that we'd build an EDSL for package configurations. Original cabal code would probably look like: main = defaultMain defaultPackageDescription{ name="foo" , synopsys="bar"} etc. Then I was hoping it would evolve to an EDSL. But most people didn't like this design. My argument was that if we created a a.cabal file, eventually the design would get more and more complex, so why not just start out with Haskell, which would give us room to grow :) But there are also lots of advantages to having the .cabal file. Maybe someone can dig up the debate on the libraries mailing list from a few years back. Anyway, with the hooks interface, you can override just about all of cabal's behavior (including inputting the description file) so there's pleanty of room to experiment with something like an EDSL. Unfortunitely your package would not be cabal-compliant without a .cabal file. We are moving more in the other direction... keeping all of the information in .cabal and not requiring a Setup.lhs file. That seems to be easier for most people. peace, isaac