better nukefile

Fixed handling of case when file does not exist to work like it did before,
and avoid an excess stat call.
This commit is contained in:
Joey Hess 2013-05-21 13:03:46 -04:00
parent b78813af3a
commit 822a8c0ff8
2 changed files with 11 additions and 2 deletions

View file

@ -12,6 +12,8 @@ module Utility.Exception where
import Prelude hiding (catch)
import Control.Exception
import Control.Applicative
import Control.Monad
import System.IO.Error (isDoesNotExistError)
{- Catches IO errors and returns a Bool -}
catchBoolIO :: IO Bool -> IO Bool
@ -49,3 +51,8 @@ catchNonAsync a onerr = a `catches`
tryNonAsync :: IO a -> IO (Either SomeException a)
tryNonAsync a = (Right <$> a) `catchNonAsync` (return . Left)
{- Catches only DoesNotExist exceptions, and lets all others through. -}
tryWhenExists :: IO a -> IO (Maybe a)
tryWhenExists a = either (const Nothing) Just <$>
tryJust (guard . isDoesNotExistError) a