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-rw-r--r--src/Utility/Exception.hs75
1 files changed, 52 insertions, 23 deletions
diff --git a/src/Utility/Exception.hs b/src/Utility/Exception.hs
index c6510dbc..ab47ae95 100644
--- a/src/Utility/Exception.hs
+++ b/src/Utility/Exception.hs
@@ -1,59 +1,88 @@
{- Simple IO exception handling (and some more)
-
- - Copyright 2011-2012 Joey Hess <id@joeyh.name>
+ - Copyright 2011-2014 Joey Hess <id@joeyh.name>
-
- License: BSD-2-clause
-}
{-# LANGUAGE ScopedTypeVariables #-}
-module Utility.Exception where
+module Utility.Exception (
+ module X,
+ catchBoolIO,
+ catchMaybeIO,
+ catchDefaultIO,
+ catchMsgIO,
+ catchIO,
+ tryIO,
+ bracketIO,
+ catchNonAsync,
+ tryNonAsync,
+ tryWhenExists,
+) where
-import Control.Exception
-import qualified Control.Exception as E
-import Control.Applicative
+import Control.Monad.Catch as X hiding (Handler)
+import qualified Control.Monad.Catch as M
+import Control.Exception (IOException, AsyncException)
import Control.Monad
+import Control.Monad.IO.Class (liftIO, MonadIO)
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 = M.catch
{- try specialized for IO errors only -}
-tryIO :: IO a -> IO (Either IOException a)
-tryIO = try
+tryIO :: MonadCatch m => m a -> m (Either IOException a)
+tryIO = M.try
+
+{- bracket with setup and cleanup actions lifted to IO.
+ -
+ - Note that unlike catchIO and tryIO, this catches all exceptions. -}
+bracketIO :: (MonadMask m, MonadIO m) => IO v -> (v -> IO b) -> (v -> m a) -> m a
+bracketIO setup cleanup = bracket (liftIO setup) (liftIO . cleanup)
{- 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 :: SomeException) -> onerr e)
+ [ M.Handler (\ (e :: AsyncException) -> throwM e)
+ , M.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)