diff options
Diffstat (limited to 'src/Propellor/Property/File.hs')
| -rw-r--r-- | src/Propellor/Property/File.hs | 43 |
1 files changed, 27 insertions, 16 deletions
diff --git a/src/Propellor/Property/File.hs b/src/Propellor/Property/File.hs index f774272c..12a3e80a 100644 --- a/src/Propellor/Property/File.hs +++ b/src/Propellor/Property/File.hs @@ -82,12 +82,11 @@ fileProperty' writer desc a f = property desc $ go =<< liftIO (doesFileExist f) let new = unlines (a (lines old)) if old == new then noChange - else makeChange $ viaTmp updatefile f new + else makeChange $ updatefile new `viaStableTmp` f go False = makeChange $ writer f (unlines $ a []) - -- viaTmp makes the temp file mode 600. -- Replicate the original file's owner and mode. - updatefile f' content = do + updatefile content f' = do writer f' content s <- getFileStatus f setFileMode f' (fileMode s) @@ -119,19 +118,7 @@ link `isSymlinkedTo` target = property desc $ if target == target' then noChange else makeChange updateLink - updateLink = bracket_ setup cleanup $ rename link' link - link' = link ++ ".propellor-new~" - setup = do - whenM hasOldLink' removeOldLink' - createSymbolicLink target link' - cleanup = tryIO $ removeLink link' - hasOldLink' = (tryIO $ getSymbolicLinkStatus link') >>= \result -> - case result of - Right stat -> return $ isSymbolicLink stat - Left _ -> return False - removeOldLink' = do - warningMessage $ "removing cruft from previous run: " ++ link' - removeLink link' + updateLink = createSymbolicLink target `viaStableTmp` link -- | Ensures that a file/dir has the specified owner and group. ownerGroup :: FilePath -> User -> Group -> Property NoInfo @@ -148,3 +135,27 @@ mode :: FilePath -> FileMode -> Property NoInfo mode f v = property (f ++ " mode " ++ show v) $ do liftIO $ modifyFileMode f (const v) noChange + +-- | A temp file to use when writing new content for a file. +-- +-- This is a stable name so it can be removed idempotently. +-- +-- It ends with "~" so that programs that read many config files from a +-- directory will treat it as an editor backup file, and not read it. +stableTmpFor :: FilePath -> FilePath +stableTmpFor f = f ++ ".propellor-new~" + +-- | Creates/updates a file atomically, running the action to create the +-- stable tmp file, and then renaming it into place. +viaStableTmp :: (MonadMask m, MonadIO m) => (FilePath -> m ()) -> FilePath -> m () +viaStableTmp a f = bracketIO setup cleanup go + where + setup = do + createDirectoryIfMissing True (takeDirectory f) + let tmpfile = stableTmpFor f + nukeFile tmpfile + return tmpfile + cleanup tmpfile = tryIO $ removeFile tmpfile + go tmpfile = do + a tmpfile + liftIO $ rename tmpfile f |