diff options
| -rw-r--r-- | Utility/Exception.hs | 49 |
1 files changed, 29 insertions, 20 deletions
diff --git a/Utility/Exception.hs b/Utility/Exception.hs index 1fecf65d5..13c9d508a 100644 --- a/Utility/Exception.hs +++ b/Utility/Exception.hs @@ -1,6 +1,6 @@ {- Simple IO exception handling (and some more) - - - Copyright 2011-2012 Joey Hess <joey@kitenet.net> + - Copyright 2011-2014 Joey Hess <joey@kitenet.net> - - License: BSD-2-clause -} @@ -9,51 +9,60 @@ module Utility.Exception where -import Control.Exception -import qualified Control.Exception as E -import Control.Applicative +import Control.Exception (IOException, AsyncException) +import Control.Monad.Catch import Control.Monad import System.IO.Error (isDoesNotExistError) import Utility.Data {- Catches IO errors and returns a Bool -} -catchBoolIO :: IO Bool -> IO Bool +catchBoolIO :: MonadCatch m => m Bool -> m Bool catchBoolIO = catchDefaultIO False {- Catches IO errors and returns a Maybe -} -catchMaybeIO :: IO a -> IO (Maybe a) -catchMaybeIO a = catchDefaultIO Nothing $ Just <$> a +catchMaybeIO :: MonadCatch m => m a -> m (Maybe a) +catchMaybeIO a = do + catchDefaultIO Nothing $ do + v <- a + return (Just v) {- Catches IO errors and returns a default value. -} -catchDefaultIO :: a -> IO a -> IO a +catchDefaultIO :: MonadCatch m => a -> m a -> m 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 +catchMsgIO :: MonadCatch m => m a -> m (Either String a) +catchMsgIO a = do + v <- tryIO a + return $ either (Left . show) Right v {- catch specialized for IO errors only -} -catchIO :: IO a -> (IOException -> IO a) -> IO a -catchIO = E.catch +catchIO :: MonadCatch m => m a -> (IOException -> m a) -> m a +catchIO = catch {- try specialized for IO errors only -} -tryIO :: IO a -> IO (Either IOException a) +tryIO :: MonadCatch m => m a -> m (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 :: MonadCatch m => m a -> (SomeException -> m a) -> m a catchNonAsync a onerr = a `catches` - [ Handler (\ (e :: AsyncException) -> throw e) + [ Handler (\ (e :: AsyncException) -> throwM e) , Handler (\ (e :: SomeException) -> onerr e) ] -tryNonAsync :: IO a -> IO (Either SomeException a) -tryNonAsync a = (Right <$> a) `catchNonAsync` (return . Left) +tryNonAsync :: MonadCatch m => m a -> m (Either SomeException a) +tryNonAsync a = go `catchNonAsync` (return . Left) + where + go = do + v <- a + return (Right v) {- Catches only DoesNotExist exceptions, and lets all others through. -} -tryWhenExists :: IO a -> IO (Maybe a) -tryWhenExists a = eitherToMaybe <$> - tryJust (guard . isDoesNotExistError) a +tryWhenExists :: MonadCatch m => m a -> m (Maybe a) +tryWhenExists a = do + v <- tryJust (guard . isDoesNotExistError) a + return (eitherToMaybe v) |