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-rw-r--r--src/Propellor/Property/File.hs52
1 files changed, 49 insertions, 3 deletions
diff --git a/src/Propellor/Property/File.hs b/src/Propellor/Property/File.hs
index b491ccbe..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)
@@ -98,6 +97,29 @@ dirExists :: FilePath -> Property NoInfo
dirExists d = check (not <$> doesDirectoryExist d) $ property (d ++ " exists") $
makeChange $ createDirectoryIfMissing True d
+-- | Creates or atomically updates a symbolic link. Does not overwrite regular
+-- files or directories.
+isSymlinkedTo :: FilePath -> FilePath -> Property NoInfo
+link `isSymlinkedTo` target = property desc $
+ go =<< (liftIO $ tryIO $ getSymbolicLinkStatus link)
+ where
+ desc = link ++ " is symlinked to " ++ target
+ go (Right stat) =
+ if isSymbolicLink stat
+ then checkLink
+ else nonSymlinkExists
+ go (Left _) = makeChange $ createSymbolicLink target link
+
+ nonSymlinkExists = do
+ warningMessage $ link ++ " exists and is not a symlink"
+ return FailedChange
+ checkLink = do
+ target' <- liftIO $ readSymbolicLink link
+ if target == target'
+ then noChange
+ else makeChange updateLink
+ updateLink = createSymbolicLink target `viaStableTmp` link
+
-- | Ensures that a file/dir has the specified owner and group.
ownerGroup :: FilePath -> User -> Group -> Property NoInfo
ownerGroup f (User owner) (Group group) = property (f ++ " owner " ++ og) $ do
@@ -113,3 +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