Add support for shebang at start of file

Fixes #86

1 files changed, 11 insertions, 2 deletions

diff --git a/src/Language/Haskell/Stylish/Parse.hs b/src/Language/Haskell/Stylish/Parse.hs
index 8b3d34b..a3ef579 100644
--- a/src/Language/Haskell/Stylish/Parse.hs
+++ b/src/Language/Haskell/Stylish/Parse.hs
@@ -7,6 +7,7 @@ module Language.Haskell.Stylish.Parse
 --------------------------------------------------------------------------------
 import           Data.Maybe                      (fromMaybe, listToMaybe)
 import qualified Language.Haskell.Exts.Annotated as H
+import Data.List (isPrefixOf)
 
 
 --------------------------------------------------------------------------------
@@ -27,6 +28,14 @@ unCpp = unlines . go False . lines
 
 
 --------------------------------------------------------------------------------
+-- | Remove shebang from the first line
+unShebang :: String -> String
+unShebang str
+    | "#!" `isPrefixOf` str = unlines $ drop 1 $ lines str
+    | otherwise             = str
+
+
+--------------------------------------------------------------------------------
 -- | If the given string is prefixed with an UTF-8 Byte Order Mark, drop it
 -- because haskell-src-exts can't handle it.
 dropBom :: String -> String
@@ -55,10 +64,10 @@ parseModule extraExts mfp string = do
             }
 
         -- Preprocessing
-        noCpp    =
+        processed = unShebang $
             if H.EnableExtension H.CPP `elem` exts then unCpp noBom else noBom
 
-    case H.parseModuleWithComments mode noCpp of
+    case H.parseModuleWithComments mode processed of
         H.ParseOk md -> return md
         err          -> Left $
             "Language.Haskell.Stylish.Parse.parseModule: could not parse " ++