[Haskell-cafe] HookedBuildInfo and Cabal

[Duncan Coutts]

On Thu, 2009-01-08 at 12:42 -0600, John Goerzen wrote:

> As a more general question, how can one use Cabal to detect PostgreSQL
> paths in a way that works with both GHC 6.8 and 6.10?

Yes:

The following is using "build-type: Simple" in HDBC-postgresql.cabal and
it does not use HDBC-postgresql.buildinfo.in or the other autoconf
files.

Note that I've not actually tested that this builds HDBC-postgresql
fully (I don't have postgres installed). But with a suitable hacked up
pgconfig/pg_config on the $PATH that it does pass the output to ghc,
hsc2hs etc. It works with Cabal-1.2 and 1.6.

I've not done it but you can also require a minimum pgconfig version if
you modify pgconfigProgram below to discover the version number. You'd
put the following in the .cabal file:

  build-tools: pgconfig >= 7.3

or whatever.

Duncan

Setup.hs:

import Distribution.Simple
import Distribution.PackageDescription
import Distribution.Version

import Distribution.Simple.LocalBuildInfo
import Distribution.Simple.Program
import Distribution.Verbosity

import Control.Monad

main = defaultMainWithHooks simpleUserHooks {
  hookedPrograms = [pgconfigProgram],

  confHook = \pkg flags -> do
    lbi <- confHook defaultUserHooks pkg flags
    bi <- psqlBuildInfo lbi
    return lbi {
      localPkgDescr = updatePackageDescription
                        (Just bi, []) (localPkgDescr lbi)
    } 
}

pgconfigProgram = (simpleProgram "pgconfig") {
    programFindLocation = \verbosity -> do
      pgconfig  <- findProgramOnPath "pgconfig"  verbosity 
      pg_config <- findProgramOnPath "pg_config" verbosity
      return (pgconfig `mplus` pg_config)
  }

psqlBuildInfo :: LocalBuildInfo -> IO BuildInfo
psqlBuildInfo lbi = do
  (pgconfigProg, _) <- requireProgram verbosity
                         pgconfigProgram AnyVersion (withPrograms lbi)
  let pgconfig = rawSystemProgramStdout verbosity pgconfigProg

  incDir <- pgconfig ["--includedir"]
  libDir <- pgconfig ["--libdir"]

  return emptyBuildInfo {
    extraLibDirs = [libDir],
    includeDirs  = [incDir]
  }
  where
    verbosity = normal -- honestly, this is a hack