Fix build on case-insensitive filesystems (#873)

GhcModExe/Lint.hs

@@ -0,0 +1,30 @@
+module GhcModExe.Lint where
+
+import Exception (ghandle)
+import Control.Exception (SomeException(..))
+import Language.Haskell.GhcMod.Logger (checkErrorPrefix)
+import Language.Haskell.GhcMod.Convert
+import Language.Haskell.GhcMod.Types
+import Language.Haskell.GhcMod.Monad
+import Language.Haskell.HLint3
+
+import Language.Haskell.GhcMod.Utils (withMappedFile)
+import Language.Haskell.Exts.SrcLoc (SrcSpan(..))
+
+-- | Checking syntax of a target file using hlint.
+--   Warnings and errors are returned.
+lint :: IOish m
+     => LintOpts  -- ^ Configuration parameters
+     -> FilePath  -- ^ A target file.
+     -> GhcModT m String
+lint opt file = ghandle handler $
+  withMappedFile file $ \tempfile -> do
+    res <- liftIO $ hlint $ "--quiet" : tempfile : optLintHlintOpts opt
+    pack . map (show . substFile file tempfile) $ res
+  where
+    pack = convert' . map init -- init drops the last \n.
+    handler (SomeException e) = return $ checkErrorPrefix ++ show e ++ "\n"
+    substFile orig temp idea
+      | srcSpanFilename (ideaSpan idea) == temp
+      = idea{ideaSpan=(ideaSpan idea){srcSpanFilename = orig}}
+    substFile _ _ idea = idea