The other day I noted that I couldn't install the darcs version of Happstack on my windows machine. There was a build failure that was reported on the mailing list. So I waited a few days, and tried again. But then, before I started building Happstack, something happened. I don't exactly remember what, I think I was a bit to eager with cabal upgrade, and I upgraded some base packages that I shouldn't have. I remember directory-1.0.1.1 failing to build and having to go through MSYS to get it to build. Then more and more things needed to be upgraded and ghc-pkg check was reporting more and more weird things. When I thought I had upgraded everything, I tried happstack. happstack-util built, but then happstack-data reported that happstack-util couldn't be built because it required both time-1.1.4 and time-2-something. Oh oh. I screwed around for a while. Then I saw some posts on the web talking about removing package.conf.d. In my random experiments with cabal upgrade I had managed to install everything in my user profile and not inside my Haskell Platform directory, so there was hope!
I deleted package.conf.d. ghc-pkg list reported a saner list of packages. I tried building happstack again. Then something "funny" happened: every cabal build I was trying to do first tried to reinstall process-1.0.1.2, and failed every time!! And of course process-1.0.1.2 appeared in the ouput of ghc-pkg list... WTF? Ah, ok, directory-1.0.1.1 is still installed, let's kill the beast! And then everything worked! Happstack built, happstack "hello world" server even runs, life is happy again!
I didn't try to investigate why Cabal or directory-1.0.1.1 were insisting on reinstalling something that I have already. I've seen enough weird things and spent enough time this week away from the nice world of pure lazy functional programming and in dirty low-level configuration and build issues to not care too much anymore...