[commit: packages/Cabal] ghc-head: New helper function: removeExistingFile. (8e4227a)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/Cabal

On branch  : ghc-head
Link       : http://git.haskell.org/?p=packages/Cabal.git;a=commit;h=8e4227ac8a4f41cc09da00f2bc6adcb045dd175f

>---------------------------------------------------------------

commit 8e4227ac8a4f41cc09da00f2bc6adcb045dd175f
Author: Mikhail Glushenkov <mikhail.glushenkov at gmail.com>
Date:   Wed May 29 01:15:14 2013 +0200

    New helper function: removeExistingFile.


>---------------------------------------------------------------

8e4227ac8a4f41cc09da00f2bc6adcb045dd175f
 cabal-install/Distribution/Client/Utils.hs |   13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/cabal-install/Distribution/Client/Utils.hs b/cabal-install/Distribution/Client/Utils.hs
index 49c5f2c..20c6e05 100644
--- a/cabal-install/Distribution/Client/Utils.hs
+++ b/cabal-install/Distribution/Client/Utils.hs
@@ -3,11 +3,14 @@
 module Distribution.Client.Utils ( MergeResult(..)
                                  , mergeBy, duplicates, duplicatesBy
                                  , moreRecentFile, inDir, numberOfProcessors
+                                 , removeExistingFile
                                  , makeAbsoluteToCwd, filePathToByteString
                                  , byteStringToFilePath, tryCanonicalizePath)
        where
 
 import qualified Data.ByteString.Lazy as BS
+import Control.Monad
+         ( when )
 import Data.Bits
          ( (.|.), shiftL, shiftR )
 import Data.Char
@@ -21,7 +24,7 @@ import qualified Control.Exception as Exception
          ( finally )
 import System.Directory
          ( canonicalizePath, doesFileExist, getModificationTime
-         , getCurrentDirectory, setCurrentDirectory )
+         , getCurrentDirectory, removeFile, setCurrentDirectory )
 import System.FilePath
          ( (</>), isAbsolute )
 import System.IO.Unsafe ( unsafePerformIO )
@@ -74,6 +77,14 @@ moreRecentFile a b = do
             ta <- getModificationTime a
             return (ta > tb)
 
+-- | Like 'removeFile', but does not throw an exception when the file does not
+-- exist.
+removeExistingFile :: FilePath -> IO ()
+removeExistingFile path = do
+  exists <- doesFileExist path
+  when exists $
+    removeFile path
+
 -- | Executes the action in the specified directory.
 inDir :: Maybe FilePath -> IO a -> IO a
 inDir Nothing m = m