From be02ef96aa89a6af554a622f266d700ac0c98fdf Mon Sep 17 00:00:00 2001
From: Joey Hess <joeyh@debian.org>
Date: Fri, 11 Apr 2014 01:19:05 -0400
Subject: propellor (0.3.0) unstable; urgency=medium

  * ipv6to4: Ensure interface is brought up automatically on boot.
  * Enabling unattended upgrades now ensures that cron is installed and
    running to perform them.
  * Properties can be scheduled to only be checked after a given time period.
  * Fix bootstrapping of dependencies.
  * Fix compilation on Debian stable.
  * Include security updates in sources.list for stable and testing.
  * Use ssh connection caching, especially when bootstrapping.
  * Properties now run in a Propellor monad, which provides access to
    attributes of the host.

# imported from the archive
---
 Utility/Exception.hs | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)
 create mode 100644 Utility/Exception.hs

(limited to 'Utility/Exception.hs')

diff --git a/Utility/Exception.hs b/Utility/Exception.hs
new file mode 100644
index 00000000..cf2c615c
--- /dev/null
+++ b/Utility/Exception.hs
@@ -0,0 +1,59 @@
+{- 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
-- 
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