Take Haskell2010 extension into account

Closes #36

2 files changed, 32 insertions, 1 deletions

diff --git a/src/Language/Haskell/Stylish/Parse.hs b/src/Language/Haskell/Stylish/Parse.hs
index 5162527..d9e0c9b 100644
--- a/src/Language/Haskell/Stylish/Parse.hs
+++ b/src/Language/Haskell/Stylish/Parse.hs
@@ -36,6 +36,27 @@ dropBom str              = str
 
 
 --------------------------------------------------------------------------------
+-- | If
+--
+-- > {-# LANGUAGE Haskell2010 #-}
+--
+-- is specified, we need to add a number of extra extensions
+addHaskell2010Extensions :: [H.Extension] -> [H.Extension]
+addHaskell2010Extensions exts
+    -- For some reason Haskell2010 is not supported yet in haskell-src-exts
+    | H.UnknownExtension "Haskell2010" `elem` exts = exts ++ extra
+    | otherwise                                    = exts
+  where
+    extra =
+        [ H.PatternGuards
+        , H.RelaxedPolyRec
+        , H.EmptyDataDecls
+        , H.ForeignFunctionInterface
+        , H.UnknownExtension "NoNPlusKPatterns"  -- Not supported yet in HSE
+        ]
+
+
+--------------------------------------------------------------------------------
 -- | Abstraction over HSE's parsing
 parseModule :: Extensions -> Maybe FilePath -> String -> Either String Module
 parseModule extraExts mfp string = do
@@ -43,7 +64,7 @@ parseModule extraExts mfp string = do
     let noBom      = dropBom string
         extraExts' = map H.classifyExtension extraExts
         fileExts   = fromMaybe [] $ H.readExtensions noBom
-        exts       = fileExts ++ extraExts'
+        exts       = addHaskell2010Extensions $ fileExts ++ extraExts'
 
         -- Parsing options...
         fp       = fromMaybe "<unknown>" mfp
diff --git a/tests/Language/Haskell/Stylish/Parse/Tests.hs b/tests/Language/Haskell/Stylish/Parse/Tests.hs
index cd026fd..718c7f6 100644
--- a/tests/Language/Haskell/Stylish/Parse/Tests.hs
+++ b/tests/Language/Haskell/Stylish/Parse/Tests.hs
@@ -20,6 +20,7 @@ tests = testGroup "Language.Haskell.Stylish.Parse"
     [ testCase "UTF-8 Byte Order Mark" testBom
     , testCase "Extra extensions"      testExtraExtensions
     , testCase "Multiline CPP"         testMultilineCpp
+    , testCase "Haskell2010 extension" testHaskell2010
     ]
 
 
@@ -49,6 +50,15 @@ testMultilineCpp = assert $ isRight $ parseModule [] Nothing $ unlines
 
 
 --------------------------------------------------------------------------------
+testHaskell2010 :: Assertion
+testHaskell2010 = assert $ isRight $ parseModule [] Nothing $ unlines
+    [ "{-# LANGUAGE Haskell2010 #-}"
+    , "module X where"
+    , "foo x | Just y <- x = y"
+    ]
+
+
+--------------------------------------------------------------------------------
 isRight :: Either a b -> Bool
 isRight (Right _) = True
 isRight _         = False