repa: we have two different versions for ghc <7.2 and >=7.2 about cabal2nix HOT 8 CLOSED

I don't like the alternative.

Setting the defaults correctly for the two version is the way to go. One thing we can additionally add is the ability to remove versions in the defaults. So in the old ghc versions, we'd remove the versions that are known to fail. What we can already do is set it to low prio in this case.

from cabal2nix.

I experimented a little, and I think I see the situation more clearly now. There are two distinct problems that we'd like to solve:

• Some packages compile only with specific versions of GHC. haskell-yap, for example, requires GHC >= 7.2.1. The WebServer package, on the other hand, requires GHC <= 6.12.3. We know this, but our package database doesn't reflect that know-how:

  $ nix-env -qa \* | grep haskell-yap
  haskell-yap-ghc6.10.4-0.0
  haskell-yap-ghc6.12.3-0.0
  haskell-yap-ghc7.0.4-0.0
  haskell-yap-ghc7.0.4-0.0-profiling
  haskell-yap-ghc7.2.1-0.0

  4 out of those 5 build are not going to work, which is not exactly a user-friendly situation. (Another side of this issue is that Hydra attempts performs all those build unnecessarily, too.)

• Some packages place different versions constraints on their dependencies depending on which compiler is build them. repa-examples, for instance, needs different versions of repa when it's built with 7.0.2 or 7.2.1. We can configure that kind of thing with compiler specific overrides in haskellPlatformDefaults, etc., so this is no big deal.

So, basically, haskellPlatformDefaults solves the second problem, but not the first one. To remedy issue (1), we need the ability to define packages in a way that makes them show visible only for those compilers that can actually build them.

from cabal2nix.

Lacking a better alternative, I've opted to drop supporting repa on GHC 7.0.4. New releases require the latest version of the compiler, and maintaining multiple version of repa -- which comes split over 4 different packages -- feels like a major effort.

from cabal2nix.

Lacking a better alternative, I've opted to drop supporting repa on GHC 7.0.4. New releases require the latest version of the compiler, and maintaining multiple version of repa -- which comes split over 4 different packages -- feels like a major effort.

I don't like this one. I am using repa, and I'm using ghc-7.0.4,
because I can hardly recommend ghc-7.2.1 yet to clients. So while
ghc-7.0.4 is our "default version", I don't think we should include
more recent packages if that means dropping compatibility with
ghc-7.0.4.

Cheers,
Andres

from cabal2nix.

Well, the latest version of repa is a major update, and the problems with GHC 7.0.4 are not going to go away any time soon. What do you suggest we do? Being stuck with an old version of the package doesn't seem like a good idea. As far as I can tell, the only way to remedy the situation is too maintain two versions of repa in parallel. Are you willing to do that?

from cabal2nix.

Well, the latest version of repa is a major update, and the problems with GHC 7.0.4 are not going to go away any time soon. What do you suggest we do? Being stuck with an old version of the package doesn't seem like a good idea. As far as I can tell, the only way to remedy the situation is too maintain two versions of repa in parallel. Are you willing to do that?

If necessary, yes. What in our current setup is it that makes
maintaining two versions of a package particularly difficult?

Andres

from cabal2nix.

Well, it's 4 different repa packages, and the different versions require different versions of vector, so figuring out the correct overrides is a bit of an effort. Also, there is the issue that nix-env -u * shouldn't be completely broken.

from cabal2nix.

Well, it's 4 different repa packages, and the different versions require different versions of vector, so figuring out the correct overrides is a bit of an effort. Also, there is the issue that nix-env -u * shouldn't be completely broken.

Alright :) Leave it as it is then. I'll add the older versions back if
I need them.

Andres

from cabal2nix.