Development/Shake/Rerun.hs

{-# LANGUAGE MultiParamTypeClasses, GeneralizedNewtypeDeriving, DeriveDataTypeable, ScopedTypeVariables #-}

module Development.Shake.Rerun(
 defaultRuleRerun, alwaysRerun
 ) where

import Development.Shake.Core
import Development.Shake.Classes


newtype AlwaysRerunQ = AlwaysRerunQ ()
 deriving (Typeable,Eq,Hashable,Binary,NFData)
instance Show AlwaysRerunQ where show _ = "alwaysRerun"

newtype AlwaysRerunA = AlwaysRerunA ()
 deriving (Typeable,Hashable,Binary,NFData)
instance Show AlwaysRerunA where show _ = "<none>"
instance Eq AlwaysRerunA where a == b = False

instance Rule AlwaysRerunQ AlwaysRerunA where
 storedValue _ = return Nothing


-- | Always rerun the associated action. Useful for defining rules that query
-- the environment. For example:
--
-- @
-- \"ghcVersion.txt\" 'Development.Shake.*>' \\out -> do
-- 'alwaysRerun'
-- 'Development.Shake.Stdout' stdout <- 'Development.Shake.cmd' \"ghc --numeric-version\"
-- 'Development.Shake.writeFileChanged' out stdout
-- @
alwaysRerun :: Action ()
alwaysRerun = do AlwaysRerunA _ <- apply1 $ AlwaysRerunQ (); return ()

defaultRuleRerun :: Rules ()
defaultRuleRerun = defaultRule $ \AlwaysRerunQ{} -> Just $ return $ AlwaysRerunA()