On Sun, Nov 7, 2010 at 3:58 PM, wren ng thornton
On 11/7/10 11:54 AM, Henning Thielemann wrote:
Awful - I would not like to complicate my Cabal files this way. This is like copying the Build-Depends enumeration to all depending packages.
Oh, I agree :)
I wonder if you can include ghc in the build-tools: field and whether cabal-install bases its decisions on that field...
You can include ghc in that list, but I haven't been able to test to see if it changes the way cabal decides on installable packages. I doubt it. Tangentially -- you can add any program you wish to that field, but a little setup.hs hacking is necessary to get the version requirements check to work properly. Here's an example that checks for bnfc: main = do defaultMainWithHooks simpleUserHooks { hookedPrograms = [bnfcProgram] } bnfcProgram :: Program bnfcProgram = (simpleProgram "bnfc") { -- this assumes that --numeric-version prints *only* the dot-separated version id (eg: 6.12.0) programFindVersion = findProgramVersion "--numeric-version" id } With that in Setup.hs, you can specify version requirements in your cabal file as you normally would: eg: Build-tools: bnfc >= 2.4.2.0 && <= 2.5 Unfortunately, I don't know of any good way to share that Setup.hs code across multiple projects. --Rogan
Another option might be to have users set the preference: field in ~/.cabal/config. Though that requires user action again...
Why is the package ghc version specific anyways? Is it just a language extension thing?
Does the LanguageExtensions field prevent building a package, if the installed compiler cannot handle that? I'm afraid, LanguageExtensions is just a list of flags that is passed to GHC. But it sounds like a good idea, if Cabal would also check, whether the used compiler supports the required LanguageExtensions at all.
If you just wanted to ensure that things don't build on the wrong version, then you could always use a custom Setup.hs and use CPP to choose between exitSuccess and exitFailure somewhere along the way.
-- Live well, ~wren _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe