On Sat, 2008-04-12 at 23:33 -0500, Galchin, Vasili wrote:
2) This strongly looks like the package database manager, i.e. ghc-pkg. Source please so I can understand where this d*amn "unknown package: unix-2.3.0.0" message is coming from and why?
Yes, ghc/ghc-pkg is giving this message because you're trying to use a package that depends on a package that you unregistered. In your case, you unregistered unix-2.3.0.0 but process-1.0.0.0 depended on that. Cabal depends on process-1.0.0.0 which means you now cannot runghc Setup.hs scripts because they all import Cabal. Look at the output of ghc-pkg list. It marks in {} the packages that are broken due to missing dependencies. Remember you also have two package databases, the per-user one and the global one. The per-user one is stored under ~/.ghc You can see the exact path in the ghc-pkg list output. The packages from the user db mask those from the global db, so if you have messed up the per-user one then you will still get problems even if you reset the global one to default. If you're just trying to get back to a known state then you can delete the per-user ghc package db. ghc-pkg will re-create it next time you register a package as a user.
3) Serious rant mode on ... I am a computer industry veteran(decades) who is trying to convince, coggle, etc. younger colleagues about the usefulness of FPLs for correctness, etc, and then => "unknown package ....".
The error messages from ghc-pkg are not very helpful and it does not prevent you from removing packages which other packages still depend on. The best advice at the moment is, don't un-register packages, at least not without considering what other packages still depend on them. There's no easy way of doing a reverse dependency lookup I think yet via ghc-pkg. You can see direct dependencies, eg $ ghc-pkg field containers depends depends: base-3.0.1.0 array-0.1.0.0 As it happens, the latest version of Cabal gives a much better error message in the case that you try to configure a package that depends on a broken package. It says exactly which package is broken due to which missing dependency. In this case we'd get a message like: The following installed packages are broken because other packages they depend on are missing. These broken packages must be rebuilt before they can be used. package process-1.0.0.0 is broken due to missing package unix-2.3.0.0 It would be nice if ghc/ghci/runghc could give a similarly helpful error message. Duncan