From fd20a9c8613533838f5d5d398cf2d31496b99b94 Mon Sep 17 00:00:00 2001
From: Tomas Janousek <tomi@nomi.cz>
Date: Sun, 31 Jan 2021 21:05:37 +0000
Subject: [PATCH] Atomic writeStateToFile

---
 src/XMonad/Operations.hs | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/XMonad/Operations.hs b/src/XMonad/Operations.hs
index fedb7192..3c08a676 100644
--- a/src/XMonad/Operations.hs
+++ b/src/XMonad/Operations.hs
@@ -79,6 +79,7 @@ import qualified Control.Exception as C
 
 import System.IO
 import System.Directory
+import System.FilePath ((<.>))
 import System.Posix.Process (executeFile)
 import Graphics.X11.Xlib
 import Graphics.X11.Xinerama (getScreenInfo)
@@ -663,7 +664,9 @@ writeStateToFile = do
     globalPath <- asks $ stateFileName . directories
     path <- fromMaybe globalPath <$> sessionStateFileName
     stateData <- gets (\s -> StateFile (wsData s) (extState s))
-    catchIO (writeFile path $ show stateData)
+    catchIO $ do
+        writeFile (path <.> "tmp") $ show stateData
+        renameFile (path <.> "tmp") path
 
 -- | Read the state of a previous xmonad instance from a file and
 -- return that state.  The state file is removed after reading it.