ed4fe02896
This is certianly a cabal bug for not passing the build options in the cabal file when building Setup.hs. And, why oh why did ghc enable this warning by default? So unhappy with this choice.
89 lines
2.5 KiB
Haskell
89 lines
2.5 KiB
Haskell
{- Simple IO exception handling (and some more)
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-
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- Copyright 2011-2014 Joey Hess <id@joeyh.name>
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-
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- License: BSD-2-clause
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-}
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{-# LANGUAGE ScopedTypeVariables #-}
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{-# OPTIONS_GHC -fno-warn-tabs #-}
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module Utility.Exception (
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module X,
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catchBoolIO,
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catchMaybeIO,
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catchDefaultIO,
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catchMsgIO,
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catchIO,
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tryIO,
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bracketIO,
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catchNonAsync,
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tryNonAsync,
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tryWhenExists,
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) where
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import Control.Monad.Catch as X hiding (Handler)
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import qualified Control.Monad.Catch as M
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import Control.Exception (IOException, AsyncException)
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import Control.Monad
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import Control.Monad.IO.Class (liftIO, MonadIO)
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import System.IO.Error (isDoesNotExistError)
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import Utility.Data
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{- Catches IO errors and returns a Bool -}
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catchBoolIO :: MonadCatch m => m Bool -> m Bool
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catchBoolIO = catchDefaultIO False
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{- Catches IO errors and returns a Maybe -}
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catchMaybeIO :: MonadCatch m => m a -> m (Maybe a)
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catchMaybeIO a = do
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catchDefaultIO Nothing $ do
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v <- a
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return (Just v)
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{- Catches IO errors and returns a default value. -}
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catchDefaultIO :: MonadCatch m => a -> m a -> m a
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catchDefaultIO def a = catchIO a (const $ return def)
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{- Catches IO errors and returns the error message. -}
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catchMsgIO :: MonadCatch m => m a -> m (Either String a)
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catchMsgIO a = do
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v <- tryIO a
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return $ either (Left . show) Right v
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{- catch specialized for IO errors only -}
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catchIO :: MonadCatch m => m a -> (IOException -> m a) -> m a
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catchIO = M.catch
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{- try specialized for IO errors only -}
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tryIO :: MonadCatch m => m a -> m (Either IOException a)
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tryIO = M.try
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{- bracket with setup and cleanup actions lifted to IO.
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-
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- Note that unlike catchIO and tryIO, this catches all exceptions. -}
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bracketIO :: (MonadMask m, MonadIO m) => IO v -> (v -> IO b) -> (v -> m a) -> m a
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bracketIO setup cleanup = bracket (liftIO setup) (liftIO . cleanup)
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{- Catches all exceptions except for async exceptions.
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- This is often better to use than catching them all, so that
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- ThreadKilled and UserInterrupt get through.
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-}
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catchNonAsync :: MonadCatch m => m a -> (SomeException -> m a) -> m a
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catchNonAsync a onerr = a `catches`
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[ M.Handler (\ (e :: AsyncException) -> throwM e)
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, M.Handler (\ (e :: SomeException) -> onerr e)
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]
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tryNonAsync :: MonadCatch m => m a -> m (Either SomeException a)
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tryNonAsync a = go `catchNonAsync` (return . Left)
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where
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go = do
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v <- a
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return (Right v)
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{- Catches only DoesNotExist exceptions, and lets all others through. -}
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tryWhenExists :: MonadCatch m => m a -> m (Maybe a)
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tryWhenExists a = do
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v <- tryJust (guard . isDoesNotExistError) a
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return (eitherToMaybe v)
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