#342: Allow automatic resolving of conditionals on more than just build-depends -----------------------------+---------------------------------------------- Reporter: duncan | Owner: Type: enhancement | Status: new Priority: normal | Milestone: Component: Cabal library | Version: HEAD Severity: normal | Keywords: Difficulty: hard (< 1 day) | Ghcversion: 6.8.2 Platform: | -----------------------------+---------------------------------------------- We have several classes of dependency that we can express in .cabal files. The most obvious is other Haskell packages via the `build-depends` field. The others are: * C libs (`extra-libraries`) * C headers (`includes`) * other build tools (`build-tools`) * pkg-config packages (`pkgconfig-depends`) * MacOS X frameworks (`frameworks`) And we may end up with more, like Windows assemblies. If we know (by domain-specific means) what dependencies are available then we should be able to automatically resolve flag conditions that depend on them. So each one is it's own namespace and they have different representations of keys. Most use a name and some a version too. Currently `finalizePackageDescription` takes a `Maybe (PackageSet pkg)` as a way of testing if deps are available. We should generalise this to a dep testing function (which is essentially what `finalizePackageDescription` turns it into internally) on a type that has alternatives for each of the dependency namespaces. If we only had to generalise it for package constraints we might go for `Dependency -> [PackageId]` but how should we do it when we have multiple namespaces and some require version constraints and others do not. -- Ticket URL: http://hackage.haskell.org/trac/hackage/ticket/342 Hackage http://haskell.org/cabal/ Hackage: Cabal and related projects