noop

Utility/Directory.hs

@@ -19,6 +19,7 @@ import Control.Applicative
 import Utility.SafeCommand
 import Utility.TempFile
 import Utility.Exception
+import Utility.Monad
 
 {- Lists the contents of a directory.
  - Unlike getDirectoryContents, paths are not relative to the directory. -}
@@ -34,7 +35,7 @@ dirContents d = map (d </>) . filter notcruft <$> getDirectoryContents d
 moveFile :: FilePath -> FilePath -> IO ()
 moveFile src dest = tryIO (rename src dest) >>= onrename
 	where
-		onrename (Right _) = return ()
+		onrename (Right _) = noop
 		onrename (Left e)
 			| isPermissionError e = rethrow
 			| isDoesNotExistError e = rethrow

Utility/Inotify.hs

@@ -56,7 +56,7 @@ watchDir' scan i test add del dir = do
 		then void $ do
 			_ <- addWatch i watchevents dir go
 			mapM walk =<< dirContents dir
-		else return ()
+		else noop
 	where
 		watchevents
 			| isJust add && isJust del =
@@ -68,19 +68,19 @@ watchDir' scan i test add del dir = do
 		recurse = watchDir' scan i test add del
 		walk f = ifM (catchBoolIO $ Files.isDirectory <$> getFileStatus f)
 			( recurse f
-			, if scan && isJust add then fromJust add f else return ()
+			, when (scan && isJust add) $ fromJust add f
 			)
 
-		go (Created { isDirectory = False }) = return ()
+		go (Created { isDirectory = False }) = noop
 		go (Created { filePath = subdir }) = Just recurse <@> subdir
 		go (Closed { maybeFilePath = Just f }) = add <@> f
 		go (MovedIn { isDirectory = False, filePath = f }) = add <@> f
 		go (MovedOut { isDirectory = False, filePath = f }) = del <@> f
 		go (Deleted { isDirectory = False, filePath = f }) = del <@> f
-		go _ = return ()
+		go _ = noop
 		
 		Just a <@> f = a $ dir </> f
-		Nothing <@> _ = return ()
+		Nothing <@> _ = noop
 
 {- Pauses the main thread, letting children run until program termination. -}
 waitForTermination :: IO ()

Utility/Monad.hs

@@ -49,3 +49,7 @@ observe observer a = do
 {- b `after` a runs first a, then b, and returns the value of a -}
 after :: Monad m => m b -> m a -> m a
 after = observe . const
+
+{- do nothing -}
+noop :: Monad m => m ()
+noop = return ()

Utility/Touch.hsc

@@ -106,9 +106,8 @@ touchBoth file atime mtime follow =
 	withFilePath file $ \f -> do
 		pokeArray ptr [atime, mtime]
 		r <- syscall f ptr
-		if (r /= 0)
-			then throwErrno "touchBoth"
-			else return ()
+		when (r /= 0) $
+			throwErrno "touchBoth"
 	where
 		syscall = if follow
 			then c_lutimes
@@ -116,6 +115,6 @@ touchBoth file atime mtime follow =
 
 #else
 #warning "utimensat and lutimes not available; building without symlink timestamp preservation support"
-touchBoth _ _ _ _ = return ()
+touchBoth _ _ _ _ = noop
 #endif
 #endif

Utility/Url.hs

@@ -17,6 +17,7 @@ import Common
 import qualified Network.Browser as Browser
 import Network.HTTP
 import Network.URI
+import Utility.Monad
 
 type URLString = String
 
@@ -95,7 +96,7 @@ request url requesttype = go 5 url
 			case rspCode rsp of
 				(3,0,x) | x /= 5 -> redir (n - 1) u rsp
 				_ -> return rsp
-		ignore = const $ return ()
+		ignore = const noop
 		redir n u rsp = case retrieveHeaders HdrLocation rsp of
 			[] -> return rsp
 			(Header _ newu:_) ->