remotedaemon: avoid extraneous stdout output

Command/TransferKeys.hs

@@ -16,8 +16,7 @@ import Logs.Location
 import Annex.Transfer
 import qualified Remote
 import Types.Key
-
-import GHC.IO.Handle
+import Utility.SimpleProtocol (ioHandles)
 
 data TransferRequest = TransferRequest Direction Remote Key AssociatedFile
 
@@ -29,7 +28,8 @@ seek :: CommandSeek
 seek = withNothing start
 
 start :: CommandStart
-start = withHandles $ \(readh, writeh) -> do
+start = do
+	(readh, writeh) <- liftIO ioHandles
 	runRequests readh writeh runner
 	stop
   where
@@ -44,21 +44,6 @@ start = withHandles $ \(readh, writeh) -> do
 			download (Remote.uuid remote) key file forwardRetry $ \p ->
 				getViaTmp key $ \t -> Remote.retrieveKeyFile remote key file t p
 
-{- stdin and stdout are connected with the caller, to be used for
- - communication with it. But doing a transfer might involve something
- - that tries to read from stdin, or write to stdout. To avoid that, close
- - stdin, and duplicate stderr to stdout. Return two new handles
- - that are duplicates of the original (stdin, stdout). -}
-withHandles :: ((Handle, Handle) -> Annex a) -> Annex a
-withHandles a = do
-	readh <- liftIO $ hDuplicate stdin
-	writeh <- liftIO $ hDuplicate stdout
-	liftIO $ do
-		nullh <- openFile devNull ReadMode
-		nullh `hDuplicateTo` stdin
-		stderr `hDuplicateTo` stdout
-	a (readh, writeh)
-
 runRequests
 	:: Handle
 	-> Handle

RemoteDaemon/Core.hs

@@ -26,18 +26,19 @@ import qualified Data.Map as M
 
 runForeground :: IO ()
 runForeground = do
+	(readh, writeh) <- ioHandles
 	ichan <- newChan :: IO (Chan Consumed)
 	ochan <- newChan :: IO (Chan Emitted)
 
 	let reader = forever $ do
-		l <- getLine
+		l <- hGetLine readh
 		case parseMessage l of
 			Nothing -> error $ "protocol error: " ++ l
 			Just cmd -> writeChan ichan cmd
 	let writer = forever $ do
 		msg <- readChan ochan
-		putStrLn $ unwords $ formatMessage msg
-		hFlush stdout
+		hPutStrLn writeh $ unwords $ formatMessage msg
+		hFlush writeh
 	let controller = runController ichan ochan
 	
 	-- If any thread fails, the rest will be killed.

Utility/SimpleProtocol.hs

@@ -16,12 +16,13 @@ module Utility.SimpleProtocol (
 	parse1,
 	parse2,
 	parse3,
+	ioHandles,
 ) where
 
-import Control.Applicative
 import Data.Char
+import GHC.IO.Handle
 
-import Utility.Misc
+import Common
 
 -- Messages that can be sent.
 class Sendable m where
@@ -73,3 +74,17 @@ parse3 mk s = mk <$> deserialize p1 <*> deserialize p2 <*> deserialize p3
 
 splitWord :: String -> (String, String)
 splitWord = separate isSpace
+
+{- When a program speaks a simple protocol over stdio, any other output
+ - to stdout (or anything that attempts to read from stdin)
+ - will mess up the protocol. To avoid that, close stdin, and 
+ - and duplicate stderr to stdout. Return two new handles
+ - that are duplicates of the original (stdin, stdout). -}
+ioHandles :: IO (Handle, Handle)
+ioHandles = do
+	readh <- hDuplicate stdin
+	writeh <- hDuplicate stdout
+	nullh <- openFile devNull ReadMode
+	nullh `hDuplicateTo` stdin
+	stderr `hDuplicateTo` stdout
+	return (readh, writeh)