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{-# LANGUAGE ScopedTypeVariables #-}
module Propellor.Exception where
import Propellor.Types
import Propellor.Types.Exception
import Propellor.Message
import Utility.Exception
import Control.Exception (AsyncException)
import Control.Monad.Catch
import Control.Monad.IO.Class (MonadIO)
-- | Catches all exceptions (except for `StopPropellorException` and
-- `AsyncException`) and returns FailedChange.
catchPropellor :: (MonadIO m, MonadCatch m) => m Result -> m Result
catchPropellor a = either err return =<< tryPropellor a
where
err e = warningMessage (show e) >> return FailedChange
catchPropellor' :: MonadCatch m => m a -> (SomeException -> m a) -> m a
catchPropellor' a onerr = a `catches`
[ Handler (\ (e :: AsyncException) -> throwM e)
, Handler (\ (e :: StopPropellorException) -> throwM e)
, Handler (\ (e :: SomeException) -> onerr e)
]
-- | Catches all exceptions (except for `StopPropellorException` and
-- `AsyncException`).
tryPropellor :: MonadCatch m => m a -> m (Either SomeException a)
tryPropellor a = (Right <$> a) `catchPropellor'` (pure . Left)
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