propellor spin

1 files changed, 18 insertions, 0 deletions

diff --git a/src/Propellor/Engine.hs b/src/Propellor/Engine.hs
index 3fa9ffc0..0cbf6247 100644
--- a/src/Propellor/Engine.hs
+++ b/src/Propellor/Engine.hs
@@ -11,12 +11,15 @@ import "mtl" Control.Monad.Reader
 import Control.Exception (bracket)
 import System.PosixCompat
 import System.Posix.IO
+import Data.Maybe
 
 import Propellor.Types
 import Propellor.Message
 import Propellor.Exception
 import Propellor.Info
 import Utility.Exception
+import Utility.PartialPrelude
+import Utility.Monad
 
 runPropellor :: Host -> Propellor a -> IO a
 runPropellor host a = runReaderT (runWithHost a) host
@@ -62,3 +65,18 @@ onlyProcess lockfile a = bracket lock unlock (const a)
 		return l
 	unlock = closeFd
 	alreadyrunning = error "Propellor is already running on this host!"
+
+-- | Reads and displays each line from the Handle, except for the last line
+-- which is a Result.
+processChainOutput :: Handle -> IO Result
+processChainOutput h = go Nothing
+  where
+	go lastline = do
+		v <- catchMaybeIO (hGetLine h)
+		case v of
+			Nothing -> pure $ fromMaybe FailedChange $
+				readish =<< lastline
+			Just s -> do
+				maybe noop putStrLn lastline
+				hFlush stdout
+				go (Just s)