Whitespace / end line cleaner. Run `Nowsp path/to/project .hs .yml`. No warranty.

Nowsp.hs

import Control.Monad (when)

import Data.Foldable (for_)

import System.Directory (doesDirectoryExist, doesFileExist, listDirectory)
import System.FilePath ((</>), takeExtension)
import System.Environment (getArgs)

inode dirAction fileAction = go
  where
    go name = do
        dirAction go name
        fileAction name

directory action dirname = do
    yes <- doesDirectoryExist dirname

    when yes $ do
        entries <- listDirectory dirname

        for_ entries (action . (dirname </>))

    return yes

only pred action filename = do
    if pred filename
    then do
        action filename

    else do
        return False

extIsOneOf exts filename = takeExtension filename `elem` exts

file filename = do
    yes <- doesFileExist filename

    when yes $ do
        text <- readFile filename

        putStr $ "Cleaning " ++ filename ++ "... "

        length text `seq` return ()

        let ls        = lines text
        let cleaned   = map noWsp ls
        let lnTrimmed = trimLn cleaned
        let finished  = unlines lnTrimmed

        if finished == text
        then do 
            putStrLn "was clean"
            
        else do
            writeFile filename finished
            putStrLn "cleaned!"

    return yes

noWsp = reverse . dropWhile (' ' ==) . reverse

trimLn = reverse . dropWhile ("" ==) . reverse

main = do
    start : exts <- getArgs

    inode directory (only (extIsOneOf exts) file) start