On Sat, 2009-11-28 at 09:29 -0800, Bryan O'Sullivan wrote:

On Fri, Nov 27, 2009 at 1:05 PM, Henning Thielemann wrote:

I found that the dependency on Cairo and GTK originates from criterion. I have to build criterion with 'cabal install -f-chart criterion'. Unfortunately I cannot do 'cabal fetch criterion' in order to look into the cabal file, before the dependencies are resolved ...

Really? If cabal fetch runs the build depsolver before trying to download a package, that seems like a bug. Have you reported it?

It's not a bug, it's a feature! :-) Henning, you want "cabal unpack" so you can study the package contents. The fetch command is mainly so you can fetch packages and then install them when you're offline. You'd be jolly annoyed if it missed dependencies. Duncan

On Sat, 2009-11-28 at 20:13 +0100, Henning Thielemann wrote:

However I have still the problem, that once criterion is installed without gtk and cairo, then 'cabal install' still wants to download them when I install packages that import 'criterion'. :-( Bug or feature?

That's a problem with the cabal-install resolver. When configuring criterion it optimistically assumes that it will be able to install the optional dependencies. I've been working on an extra bottom-up pass for the resolver that will prune packages that cannot possibly be installed. That should help in this case and for the more common case of packages that need a particular version of base. In the mean time, a workaround would be to try: $ cabal install noslow criterion -f-chart --dry-run That should make it select criterion without the chart dep, and since the deps of criterion will then not change it should end up picking the installed instance of criterion rather than rebuilding it. Another thing that'd help here, but isn't implemented, is "installed" constraints. So that you could ask it commit to using the installed instance of criterion, rather than it having the option to rebuild (which in general it needs so it can get consistent deps). Duncan