Use the cabal configuration flags where possible when finalizing the PackageDescription.

Language/Haskell/GhcMod/CabalApi.hs

@@ -17,7 +17,7 @@ import Language.Haskell.GhcMod.Gap (benchmarkBuildInfo, benchmarkTargets,
 import Language.Haskell.GhcMod.GhcPkg
 import Language.Haskell.GhcMod.Types
 
-import MonadUtils (MonadIO, liftIO)
+import MonadUtils (liftIO)
 import Control.Applicative ((<$>))
 import qualified Control.Exception as E
 import Control.Monad (filterM)
@@ -73,20 +73,22 @@ includeDirectories cdir wdir dirs = uniqueAndSort (extdirs ++ [cdir,wdir])
 ----------------------------------------------------------------
 
 -- | Parse a cabal file and return a 'PackageDescription'.
-parseCabalFile :: (MonadIO m, Error e,  MonadError e m)
-               => FilePath
+parseCabalFile :: (IOish m, MonadError GhcModError m)
+               => Cradle
+               -> FilePath
                -> m PackageDescription
-parseCabalFile file = do
+parseCabalFile cradle file = do
     cid <- liftIO getGHCId
     epgd <- liftIO $ readPackageDescription silent file
-    case toPkgDesc cid epgd of
+    flags <- cabalConfigFlags cradle
+    case toPkgDesc cid flags epgd of
         Left deps    -> fail $ show deps ++ " are not installed"
         Right (pd,_) -> if nullPkg pd
                         then fail $ file ++ " is broken"
                         else return pd
   where
-    toPkgDesc cid =
-        finalizePackageDescription [] (const True) buildPlatform cid []
+    toPkgDesc cid flags =
+        finalizePackageDescription flags (const True) buildPlatform cid []
     nullPkg pd = name == ""
       where
         PackageName name = C.pkgName (P.package pd)

Language/Haskell/GhcMod/CabalConfig.hs

@@ -5,6 +5,7 @@
 module Language.Haskell.GhcMod.CabalConfig (
     CabalConfig
   , cabalConfigDependencies
+  , cabalConfigFlags
   ) where
 
 import Language.Haskell.GhcMod.Error
@@ -32,6 +33,7 @@ import Data.Set ()
 import Data.List (find,tails,isPrefixOf,isInfixOf,nub,stripPrefix)
 import Distribution.Package (InstalledPackageId(..)
                            , PackageIdentifier)
+import Distribution.PackageDescription (FlagAssignment)
 import Distribution.Simple.BuildPaths (defaultDistPref)
 import Distribution.Simple.Configure (localBuildInfoFile)
 import Distribution.Simple.LocalBuildInfo (ComponentName)
@@ -130,6 +132,20 @@ configDependencies thisPkg config = map fromInstalledPackageId deps
            Right x -> x
            Left msg -> error $ "reading config " ++ f ++ " failed ("++msg++")"
 
+-- | Get the flag assignment from the local build info of the given cradle
+cabalConfigFlags :: (IOish m, MonadError GhcModError m)
+                 => Cradle
+                 -> m FlagAssignment
+cabalConfigFlags cradle = do
+  config <- getConfig cradle
+  case configFlags config of
+    Right x  -> return x
+    Left msg -> throwError (GMECabalFlags (GMEString msg))
+
+-- | Extract the cabal flags from the 'CabalConfig'
+configFlags :: CabalConfig -> Either String FlagAssignment
+configFlags config = readEither =<< flip extractField "configConfigurationsFlags" =<< extractField config "configFlags"
+
 -- | Find @field@ in 'CabalConfig'. Returns 'Left' containing a user readable
 -- error message with lots of context on failure.
 extractField :: CabalConfig -> String -> Either String String

Language/Haskell/GhcMod/Debug.hs

@@ -31,7 +31,7 @@ debugInfo = cradle >>= \c -> convert' =<< do
     simpleCompilerOption = options >>= \op ->
         return $ CompilerOptions (ghcUserOptions op) [] []
     fromCabalFile c = options >>= \opts -> do
-        pkgDesc <- parseCabalFile $ fromJust $ cradleCabalFile c
+        pkgDesc <- parseCabalFile c $ fromJust $ cradleCabalFile c
         getCompilerOptions (ghcUserOptions opts) c pkgDesc
 
 ----------------------------------------------------------------

Language/Haskell/GhcMod/Error.hs

@@ -18,6 +18,8 @@ data GhcModError = GMENoMsg
                  -- 'fail' calls on GhcModT.
                  | GMECabalConfigure GhcModError
                  -- ^ Configuring a cabal project failed.
+                 | GMECabalFlags GhcModError
+                 -- ^ Retrieval of the cabal configuration flags failed.
                  | GMEProcess [String] GhcModError
                  -- ^ Launching an operating system process failed. The first
                  -- field is the command.

Language/Haskell/GhcMod/Monad.hs

@@ -204,7 +204,7 @@ initializeFlagsWithCradle opt c
     cabal = isJust mCradleFile
     ghcopts = ghcUserOptions opt
     withCabal = do
-        pkgDesc <- parseCabalFile $ fromJust mCradleFile
+        pkgDesc <- parseCabalFile c $ fromJust mCradleFile
         compOpts <- getCompilerOptions ghcopts c pkgDesc
         initSession CabalPkg opt compOpts
     withSandbox = initSession SingleFile opt compOpts