Parse *.cabal file at once in initializeGHC.

Cabal.hs

@@ -2,7 +2,7 @@
 
 module Cabal (initializeGHC) where
 
-import CabalApi (cabalBuildInfo, cabalDependPackages)
+import CabalApi (cabalParseFile, cabalBuildInfo, cabalDependPackages)
 import Control.Applicative
 import Control.Exception
 import Control.Monad
@@ -31,7 +31,8 @@ initializeGHC opt fileName ghcOptions logging = withCabal ||> withoutCabal
         return (fileName,logReader)
     withCabal = do
         (owdir,cdir,cfile) <- liftIO getDirs
-        binfo@BuildInfo{..} <- liftIO $ cabalBuildInfo cfile
+        cabal <- liftIO $ cabalParseFile cfile
+        binfo@BuildInfo{..} <- liftIO $ cabalBuildInfo cabal
         let exts = map (addX . Gap.extensionToString) $ usedExtensions binfo
             lang = maybe "-XHaskell98" (addX . show) defaultLanguage
             libs = map ("-l" ++) extraLibs
@@ -40,7 +41,7 @@ initializeGHC opt fileName ghcOptions logging = withCabal ||> withoutCabal
             idirs = case hsSourceDirs of
                 []   -> [cdir,owdir]
                 dirs -> map (cdir </>) dirs ++ [owdir]
-        depPkgs   <- liftIO $ cabalDependPackages cfile
+        depPkgs   <- liftIO $ cabalDependPackages cabal
         logReader <- initSession opt gopts idirs (Just depPkgs) logging
         return (fileName,logReader)
     addX = ("-X" ++)

CabalApi.hs

@@ -1,4 +1,5 @@
 module CabalApi (
+  cabalParseFile,
   cabalBuildInfo,
   cabalDependPackages
   ) where
@@ -19,20 +20,19 @@ import Distribution.PackageDescription.Parse (readPackageDescription)
 
 ----------------------------------------------------------------
 
+cabalParseFile :: FilePath -> IO GenericPackageDescription
+cabalParseFile =  readPackageDescription silent
+
 -- Causes error, catched in the upper function.
-cabalBuildInfo :: FilePath -> IO BuildInfo
-cabalBuildInfo file = do
-    cabal <- readPackageDescription silent file
-    return . fromJust $ fromLibrary cabal <|> fromExecutable cabal
+cabalBuildInfo :: GenericPackageDescription -> IO BuildInfo
+cabalBuildInfo pd = do
+    return . fromJust $ fromLibrary pd <|> fromExecutable pd
   where
     fromLibrary c     = libBuildInfo . condTreeData <$> condLibrary c
     fromExecutable c  = buildInfo . condTreeData . snd <$> toMaybe (condExecutables c)
     toMaybe [] = Nothing
     toMaybe (x:_) = Just x
 
-parseGenericDescription :: FilePath -> IO GenericPackageDescription
-parseGenericDescription =  readPackageDescription silent
-
 getDepsOfPairs :: [(a1, CondTree v [b] a)] -> [b]
 getDepsOfPairs =  concatMap (condTreeConstraints . snd)
 
@@ -48,9 +48,8 @@ allDependsOfDescription pd =
 getDependencyPackageName :: Dependency -> String
 getDependencyPackageName (Dependency (PackageName n) _) = n
 
-cabalDependPackages :: FilePath -> IO [String]
+cabalDependPackages :: GenericPackageDescription -> IO [String]
 cabalDependPackages =
-  fmap (toList . fromList
-        . map getDependencyPackageName
-        . allDependsOfDescription)
-  . parseGenericDescription
+  return . toList . fromList
+  . map getDependencyPackageName
+  . allDependsOfDescription