{-# LANGUAGE TemplateHaskell #-}
module Main where
import Development.Shake
import Development.Shake.Persist

-- it is just example.
md5sum :: FilePath -> Action String
md5sum file = do
  Stdout out <- command [] "md5sum" [file]
  pure out

main :: IO ()
main = shakeArgs shakeOptions $ do
  want ["show", "show-th"]
  m5  <- newCachePersist "suffix" md5sum
  m5' <- $(persist [|md5sum|])
  "random-file" %> \out -> writeFile' out out
  "show" ~> do
    value <- m5 "random-file"
    liftIO $ do
      putStrLn "Notice md5sum program execution"
      putStrLn value
  "show-th" ~> do
    -- cached separately
    value <- m5' "random-file"
    liftIO $ putStrLn value