language: fix: move interface files to a different (#1074)

* language: fix: move interface files to a different

This fixes https://github.com/digital-asset/daml/issues/1009. We move
the created interface files and hie files to a hidden directory
".interfaces" when creating a package.

* removing the ifaceDir option and hardcode the dir

src/Development/IDE/Functions/Compile.hs

@@ -62,6 +62,7 @@ import           Data.Time
 import           Development.IDE.Types.SpanInfo
 import GHC.Generics (Generic)
 import           System.FilePath
+import           System.Directory
 
 -- | 'CoreModule' together with some additional information required for the
 -- conversion to DAML-LF.
@@ -274,12 +275,14 @@ mkTcModuleResult (WriteInterface writeIface) tcm = do
     nc        <- liftIO $ readIORef (hsc_NC session)
     (iface,_) <- liftIO $ mkIfaceTc session Nothing Sf_None details tcGblEnv
     liftIO $ when writeIface $ do
-        writeIfaceFile (hsc_dflags session) (replaceExtension (file tcm) ".hi") iface
+        let path = ".interfaces" </> file tcm
+        createDirectoryIfMissing True (takeDirectory path)
+        writeIfaceFile (hsc_dflags session) (replaceExtension path ".hi") iface
         -- For now, we write .hie files whenever we write .hi files which roughly corresponds to
         -- when we are building a package. It should be easily decoupable if that turns out to be
         -- useful.
         hieFile <- runHsc session $ mkHieFile (tcModSummary tcm) tcGblEnv (fromJust $ renamedSource tcm)
-        writeHieFile (replaceExtension (file tcm) ".hie") hieFile
+        writeHieFile (replaceExtension path ".hie") hieFile
     let mod_info = HomeModInfo iface details Nothing
         origNc = nsNames nc
     case lookupModuleEnv origNc (tcmModule tcm) of