Parse cabal setup-config to get depencencies

Language/Haskell/GhcMod/Utils.hs

@@ -9,6 +9,19 @@ import System.IO (hPutStrLn, stderr)
 -- dropWhileEnd is not provided prior to base 4.5.0.0.
 dropWhileEnd :: (a -> Bool) -> [a] -> [a]
 dropWhileEnd p = foldr (\x xs -> if p x && null xs then [] else x : xs) []
+
+extractParens :: String -> String
+extractParens str = extractParens' str 0
+ where
+   extractParens' :: String -> Int -> String
+   extractParens' [] _ = []
+   extractParens' (s:ss) level
+       | s `elem` "([{" = s : extractParens' ss (level+1)
+       | level == 0 = extractParens' ss 0
+       | s `elem` "}])" && level == 1 = s:[]
+       | s `elem` "}])" = s : extractParens' ss (level-1)
+       | otherwise = s : extractParens' ss level
+
 readProcess' :: String -> [String] -> IO String
 readProcess' cmd opts = do
   (rv,output,err) <- readProcessWithExitCode cmd opts ""