git-annex/Messages.hs
Joey Hess 12243d2279 Flush json output, avoiding a buffering problem that could result in doubled output.
The bug was that with --json, output lines were sometimes doubled. For
example, git annex init --json would output two lines, despite only running
one thing. Adding to the weirdness, this only occurred when the output
was redirected to a pipe or a file.

Strace showed two processes outputting the same buffered output.
The second process was this writer process (only needed to work around
bug #624389):

                _ <- forkProcess $ do
                        hPutStr toh $ unlines paths
                        hClose toh
                        exitSuccess

The doubled output occurs when this process exits, and ghc flushes the
inherited stdout buffer. Why only when piping? I don't know, but ghc may
be behaving differently when stdout is not a terminal.

While this is quite possibly a ghc bug, there is a nice fix in git-annex.
Explicitly flushing after each chunk of json is output works around the
problem, and as a side effect, json is streamed rather than being output
all at the end when performing an expensive operaition.

However, note that this means all uses of putStr in git-annex must be
explicitly flushed. The others were, already.
2011-11-25 11:51:06 -04:00

138 lines
3.2 KiB
Haskell

{- git-annex output messages
-
- Copyright 2010-2011 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Messages (
showStart,
showNote,
showAction,
showProgress,
showSideAction,
showOutput,
showLongNote,
showEndOk,
showEndFail,
showEndResult,
showErr,
warning,
indent,
maybeShowJSON,
showCustom,
showHeader,
showRaw,
setupConsole
) where
import Text.JSON
import Common
import Types
import qualified Annex
import qualified Messages.JSON as JSON
showStart :: String -> String -> Annex ()
showStart command file = handle (JSON.start command $ Just file) $
flushed $ putStr $ command ++ " " ++ file ++ " "
showNote :: String -> Annex ()
showNote s = handle (JSON.note s) $
flushed $ putStr $ "(" ++ s ++ ") "
showAction :: String -> Annex ()
showAction s = showNote $ s ++ "..."
showProgress :: Annex ()
showProgress = handle q $
flushed $ putStr "."
showSideAction :: String -> Annex ()
showSideAction s = handle q $
putStrLn $ "(" ++ s ++ "...)"
showOutput :: Annex ()
showOutput = handle q $
putStr "\n"
showLongNote :: String -> Annex ()
showLongNote s = handle (JSON.note s) $
putStrLn $ '\n' : indent s
showEndOk :: Annex ()
showEndOk = showEndResult True
showEndFail :: Annex ()
showEndFail = showEndResult False
showEndResult :: Bool -> Annex ()
showEndResult ok = handle (JSON.end ok) $ putStrLn msg
where
msg
| ok = "ok"
| otherwise = "failed"
showErr :: (Show a) => a -> Annex ()
showErr e = warning' $ "git-annex: " ++ show e
warning :: String -> Annex ()
warning = warning' . indent
warning' :: String -> Annex ()
warning' w = do
handle q $ putStr "\n"
liftIO $ do
hFlush stdout
hPutStrLn stderr w
indent :: String -> String
indent = join "\n" . map (\l -> " " ++ l) . lines
{- Shows a JSON value only when in json mode. -}
maybeShowJSON :: JSON a => [(String, a)] -> Annex ()
maybeShowJSON v = handle (JSON.add v) q
{- Performs an action that outputs nonstandard/customized output, and
- in JSON mode wraps its output in JSON.start and JSON.end, so it's
- a complete JSON document.
- This is only needed when showStart and showEndOk is not used. -}
showCustom :: String -> Annex Bool -> Annex ()
showCustom command a = do
handle (JSON.start command Nothing) q
r <- a
handle (JSON.end r) q
showHeader :: String -> Annex ()
showHeader h = handle q $
flushed $ putStr $ h ++ ": "
showRaw :: String -> Annex ()
showRaw s = handle q $ putStrLn s
{- By default, haskell honors the user's locale in its output to stdout
- and stderr. While that's great for proper unicode support, for git-annex
- all that's really needed is the ability to display simple messages
- (currently untranslated), and importantly, to display filenames exactly
- as they are written on disk, no matter what their encoding. So, force
- raw mode.
-
- NB: Once git-annex gets localized, this will need a rethink. -}
setupConsole :: IO ()
setupConsole = do
hSetBinaryMode stdout True
hSetBinaryMode stderr True
handle :: IO () -> IO () -> Annex ()
handle json normal = Annex.getState Annex.output >>= go
where
go Annex.NormalOutput = liftIO normal
go Annex.QuietOutput = q
go Annex.JSONOutput = liftIO $ flushed $ json
q :: Monad m => m ()
q = return ()
flushed :: IO () -> IO ()
flushed a = a >> hFlush stdout