60 lines
1.8 KiB
Haskell
60 lines
1.8 KiB
Haskell
|
{- Simple IO exception handling (and some more)
|
||
|
|
-
|
||
|
|
- Copyright 2011-2012 Joey Hess <joey@kitenet.net>
|
||
|
|
-
|
||
|
|
- Licensed under the GNU GPL version 3 or higher.
|
||
|
|
-}
|
||
|
|
|
||
|
|
{-# LANGUAGE ScopedTypeVariables #-}
|
||
|
|
|
||
|
|
module Utility.Exception where
|
||
|
|
|
||
|
|
import Control.Exception
|
||
|
|
import qualified Control.Exception as E
|
||
|
|
import Control.Applicative
|
||
|
|
import Control.Monad
|
||
|
|
import System.IO.Error (isDoesNotExistError)
|
||
|
|
import Utility.Data
|
||
|
|
|
||
|
|
{- Catches IO errors and returns a Bool -}
|
||
|
|
catchBoolIO :: IO Bool -> IO Bool
|
||
|
|
catchBoolIO a = catchDefaultIO False a
|
||
|
|
|
||
|
|
{- Catches IO errors and returns a Maybe -}
|
||
|
|
catchMaybeIO :: IO a -> IO (Maybe a)
|
||
|
|
catchMaybeIO a = catchDefaultIO Nothing $ Just <$> a
|
||
|
|
|
||
|
|
{- Catches IO errors and returns a default value. -}
|
||
|
|
catchDefaultIO :: a -> IO a -> IO a
|
||
|
|
catchDefaultIO def a = catchIO a (const $ return def)
|
||
|
|
|
||
|
|
{- Catches IO errors and returns the error message. -}
|
||
|
|
catchMsgIO :: IO a -> IO (Either String a)
|
||
|
|
catchMsgIO a = either (Left . show) Right <$> tryIO a
|
||
|
|
|
||
|
|
{- catch specialized for IO errors only -}
|
||
|
|
catchIO :: IO a -> (IOException -> IO a) -> IO a
|
||
|
|
catchIO = E.catch
|
||
|
|
|
||
|
|
{- try specialized for IO errors only -}
|
||
|
|
tryIO :: IO a -> IO (Either IOException a)
|
||
|
|
tryIO = try
|
||
|
|
|
||
|
|
{- Catches all exceptions except for async exceptions.
|
||
|
|
- This is often better to use than catching them all, so that
|
||
|
|
- ThreadKilled and UserInterrupt get through.
|
||
|
|
-}
|
||
|
|
catchNonAsync :: IO a -> (SomeException -> IO a) -> IO a
|
||
|
|
catchNonAsync a onerr = a `catches`
|
||
|
|
[ Handler (\ (e :: AsyncException) -> throw e)
|
||
|
|
, Handler (\ (e :: SomeException) -> onerr e)
|
||
|
|
]
|
||
|
|
|
||
|
|
tryNonAsync :: IO a -> IO (Either SomeException a)
|
||
|
|
tryNonAsync a = (Right <$> a) `catchNonAsync` (return . Left)
|
||
|
|
|
||
|
|
{- Catches only DoesNotExist exceptions, and lets all others through. -}
|
||
|
|
tryWhenExists :: IO a -> IO (Maybe a)
|
||
|
|
tryWhenExists a = eitherToMaybe <$>
|
||
|
|
tryJust (guard . isDoesNotExistError) a
|