Only add available package to ghc options

Fixes #185

Language/Haskell/GhcMod/CabalApi.hs

@@ -39,10 +39,14 @@ import System.FilePath (dropExtension, takeFileName, (</>))
 ----------------------------------------------------------------
 
 -- | Getting necessary 'CompilerOptions' from three information sources.
-getCompilerOptions :: [GHCOption] -> Cradle -> PackageDescription -> IO CompilerOptions
+getCompilerOptions :: [GHCOption]
+                   -> Cradle
+                   -> PackageDescription
+                   -> IO CompilerOptions
 getCompilerOptions ghcopts cradle pkgDesc = do
     gopts <- getGHCOptions ghcopts cradle rdir $ head buildInfos
-    return $ CompilerOptions gopts idirs depPkgs
+    dbPkgs <- getPackageDbPackages rdir
+    return $ CompilerOptions gopts idirs (depPkgs dbPkgs)
   where
     wdir       = cradleCurrentDir cradle
     rdir       = cradleRootDir    cradle
@@ -50,7 +54,12 @@ getCompilerOptions ghcopts cradle pkgDesc = do
     pkgs       = cradlePackages   cradle
     buildInfos = cabalAllBuildInfo pkgDesc
     idirs      = includeDirectories rdir wdir $ cabalSourceDirs buildInfos
-    depPkgs    = attachPackageIds pkgs $ removeThem problematicPackages $ removeMe cfile $ cabalDependPackages buildInfos
+    depPkgs ps = attachPackageIds pkgs
+                   $ removeThem problematicPackages
+                   $ removeMe cfile
+                   $ filter (`elem` ps) -- remove packages not available in any
+                                        -- package dbs
+                   $ cabalDependPackages buildInfos
 
 ----------------------------------------------------------------
 -- Dependent packages
@@ -212,4 +221,3 @@ cabalAllTargets pd = do
     getExecutableTarget exe = do
       let maybeExes = [p </> e | p <- P.hsSourceDirs $ P.buildInfo exe, e <- [P.modulePath exe]]
       liftIO $ filterM doesFileExist maybeExes
-

test/CabalApiSpec.hs

@@ -33,6 +33,7 @@ spec = do
                       }
                 res' `shouldBe` CompilerOptions {ghcOptions = ["-global-package-db", "-no-user-package-db","-package-db",cwd </> "test/data/.cabal-sandbox/i386-osx-ghc-7.6.3-packages.conf.d","-XHaskell98"], includeDirs = ["test/data","test/data/dist/build","test/data/dist/build/autogen","test/data/subdir1/subdir2","test/data/test"], depPackages = [("Cabal", Nothing), ("base", Nothing) , ("template-haskell", Nothing)]}
 
+
     describe "cabalDependPackages" $ do
         it "extracts dependent packages" $ do
             pkgs <- cabalDependPackages . cabalAllBuildInfo <$> parseCabalFile "test/data/cabalapi.cabal"