add back debug logging

Make Utility.Process wrap the parts of System.Process that I use,
and add debug logging to them.

Also wrote some higher-level code that allows running an action
with handles to a processes stdin or stdout (or both), and checking
its exit status, all in a single function call.

As a bonus, the debug logging now indicates whether the process
is being run to read from it, feed it data, chat with it (writing and
reading), or just call it for its side effect.

6 files changed, 209 insertions, 61 deletions

diff --git a/Utility/CoProcess.hs b/Utility/CoProcess.hs
index d3b0c46ef..67f861bb3 100644
--- a/Utility/CoProcess.hs
+++ b/Utility/CoProcess.hs
@@ -13,25 +13,23 @@ module Utility.CoProcess (
 	query
 ) where
 
-import System.Process
-
 import Common
 
-type CoProcessHandle = (ProcessHandle, Handle, Handle, FilePath, [String])
+type CoProcessHandle = (ProcessHandle, Handle, Handle, CreateProcess)
 
 start :: FilePath -> [String] -> IO CoProcessHandle
 start command params = do
 	(from, to, _err, pid) <- runInteractiveProcess command params Nothing Nothing
-	return (pid, to, from, command, params)
+	return (pid, to, from, proc command params)
 
 stop :: CoProcessHandle -> IO ()
-stop (pid, from, to, command, params) = do
+stop (pid, from, to, p) = do
 	hClose to
 	hClose from
-	forceSuccessProcess pid command params
+	forceSuccessProcess p pid
 
 query :: CoProcessHandle -> (Handle -> IO a) -> (Handle -> IO b) -> IO b
-query (_, from, to, _, _) send receive = do
+query (_, from, to, _) send receive = do
 	_ <- send to
 	hFlush to
 	receive from
diff --git a/Utility/Gpg.hs b/Utility/Gpg.hs
index 26ac688e3..eed77805c 100644
--- a/Utility/Gpg.hs
+++ b/Utility/Gpg.hs
@@ -13,7 +13,6 @@ import Control.Applicative
 import Control.Concurrent
 import Control.Exception (bracket)
 import System.Posix.Env (setEnv, unsetEnv, getEnv)	
-import System.Process
 
 import Common
 
@@ -39,30 +38,21 @@ stdParams params = do
 readStrict :: [CommandParam] -> IO String
 readStrict params = do
 	params' <- stdParams params
-	(_, Just from, _, pid)
-		<- createProcess (proc "gpg" params')
-			{ std_out = CreatePipe }
-	hSetBinaryMode from True
-	r <- hGetContentsStrict from
-	forceSuccessProcess pid "gpg" params'
-	return r
+	withHandle StdoutHandle createProcessSuccess (proc "gpg" params') $ \h -> do
+		hSetBinaryMode h True
+		hGetContentsStrict h
 
 {- Runs gpg, piping an input value to it, and returning its stdout,
  - strictly. -}
 pipeStrict :: [CommandParam] -> String -> IO String
 pipeStrict params input = do
 	params' <- stdParams params
-	(Just to, Just from, _, pid)
-		<- createProcess (proc "gpg" params')
-			{ std_in = CreatePipe
-			, std_out = CreatePipe }
-	hSetBinaryMode to True
-	hSetBinaryMode from True
-	hPutStr to input
-	hClose to
-	r <- hGetContentsStrict from
-	forceSuccessProcess pid "gpg" params'
-	return r
+	withBothHandles createProcessSuccess (proc "gpg" params') $ \(to, from) -> do
+		hSetBinaryMode to True
+		hSetBinaryMode from True
+		hPutStr to input
+		hClose to
+		hGetContentsStrict from
 
 {- Runs gpg with some parameters, first feeding it a passphrase via
  - --passphrase-fd, then feeding it an input, and passing a handle
@@ -82,16 +72,13 @@ passphraseHandle params passphrase a b = do
 	let passphrasefd = [Param "--passphrase-fd", Param $ show pfd]
 
 	params' <- stdParams $ passphrasefd ++ params
-	(Just toh, Just fromh, _, pid) <- createProcess (proc "gpg" params')
-		{ std_in = CreatePipe, std_out = CreatePipe }
-	L.hPut toh =<< a
-	hClose toh
-	ret <- b fromh
-
-	-- cleanup
-	forceSuccessProcess pid "gpg" params'
-	closeFd frompipe
-	return ret
+	closeFd frompipe `after`
+		withBothHandles createProcessSuccess (proc "gpg" params') go
+	where
+		go (to, from) = do
+			L.hPut to =<< a
+			hClose to
+			b from
 
 {- Finds gpg public keys matching some string. (Could be an email address,
  - a key id, or a name. -}
diff --git a/Utility/INotify.hs b/Utility/INotify.hs
index 55233ef76..66c0ab23d 100644
--- a/Utility/INotify.hs
+++ b/Utility/INotify.hs
@@ -10,7 +10,6 @@ module Utility.INotify where
 import Common hiding (isDirectory)
 import Utility.ThreadLock
 import Utility.Types.DirWatcher
-import System.Process
 
 import System.INotify
 import qualified System.Posix.Files as Files
diff --git a/Utility/Lsof.hs b/Utility/Lsof.hs
index ebd273b2e..ce6a16283 100644
--- a/Utility/Lsof.hs
+++ b/Utility/Lsof.hs
@@ -12,7 +12,6 @@ module Utility.Lsof where
 import Common
 
 import System.Posix.Types
-import System.Process
 
 data LsofOpenMode = OpenReadWrite | OpenReadOnly | OpenWriteOnly | OpenUnknown
 	deriving (Show, Eq)
@@ -34,9 +33,11 @@ queryDir path = query ["+d", path]
  - Note: If lsof is not available, this always returns [] !
  -}
 query :: [String] -> IO [(FilePath, LsofOpenMode, ProcessInfo)]
-query opts = do
-	(_, s, _) <- readProcessWithExitCode "lsof" ("-F0can" : opts) []
-	return $ parse s
+query opts =
+	withHandle StdoutHandle (createProcessChecked checkSuccessProcess) p $ \h -> do
+		parse <$> hGetContentsStrict h
+	where
+		p = proc "lsof" ("-F0can" : opts)
 
 {- Parsing null-delimited output like:
  -
diff --git a/Utility/Process.hs b/Utility/Process.hs
index 9f79efa81..9b57c3b7a 100644
--- a/Utility/Process.hs
+++ b/Utility/Process.hs
@@ -1,40 +1,202 @@
-{- System.Process enhancements
+{- System.Process enhancements, including additional ways of running
+ - processes, and logging.
  -
  - Copyright 2012 Joey Hess <joey@kitenet.net>
  -
  - Licensed under the GNU GPL version 3 or higher.
  -}
 
-module Utility.Process where
+{-# LANGUAGE Rank2Types #-}
 
-import System.Process
+module Utility.Process (
+	module X,
+	CreateProcess,
+	StdHandle(..),
+	readProcessEnv,
+	forceSuccessProcess,
+	checkSuccessProcess,
+	createProcessSuccess,
+	createProcessChecked,
+	createBackgroundProcess,
+	withHandle,
+	withBothHandles,
+	createProcess,
+	runInteractiveProcess,
+	readProcess
+) where
+
+import qualified System.Process
+import System.Process as X hiding (CreateProcess(..), createProcess, runInteractiveProcess, readProcess, readProcessWithExitCode, system, rawSystem, runInteractiveCommand, runProcess)
+import System.Process hiding (createProcess, runInteractiveProcess, readProcess, readProcessWithExitCode)
 import System.Exit
 import System.IO
+import System.Log.Logger
 
 import Utility.Misc
 
+type CreateProcessRunner = forall a. CreateProcess -> ((Maybe Handle, Maybe Handle, Maybe Handle, ProcessHandle) -> IO a) -> IO a
+
+data StdHandle = StdinHandle | StdoutHandle | StderrHandle
+	deriving (Eq)
+
+{- Like readProcess, but allows specifying the environment, and does
+ - not mess with stdin. -}
+readProcessEnv :: FilePath -> [String] -> Maybe [(String, String)] -> IO String
+readProcessEnv cmd args environ =
+	withHandle StdoutHandle createProcessSuccess p $ \h -> do
+		output  <- hGetContentsStrict h
+		hClose h
+		return output
+	where
+		p = (proc cmd args)
+			{ std_out = CreatePipe
+			, env = environ
+			}
+
 {- Waits for a ProcessHandle, and throws an exception if the process
  - did not exit successfully. -}
-forceSuccessProcess :: ProcessHandle -> String -> [String] -> IO ()
-forceSuccessProcess pid cmd args = do
+forceSuccessProcess :: CreateProcess -> ProcessHandle -> IO ()
+forceSuccessProcess p pid = do
 	code <- waitForProcess pid
 	case code of
 		ExitSuccess -> return ()
-		ExitFailure n -> error $
-			cmd ++ " " ++ show args ++ " exited " ++ show n
+		ExitFailure n -> error $ showCmd p ++ " exited " ++ show n
 
-{- Like readProcess, but allows specifying the environment, and does
- - not mess with stdin. -}
-readProcessEnv :: FilePath -> [String] -> Maybe [(String, String)] -> IO String
-readProcessEnv cmd args environ = do
-	(_, Just h, _, pid)
-		<- createProcess (proc cmd args)
-			{ std_in  = Inherit
+{- Waits for a ProcessHandle and returns True if it exited successfully. -}
+checkSuccessProcess :: ProcessHandle -> IO Bool
+checkSuccessProcess pid = do
+	code <- waitForProcess pid
+	return $ code == ExitSuccess
+
+{- Runs createProcess, then an action on its handles, and then
+ - forceSuccessProcess. -}
+createProcessSuccess :: CreateProcessRunner
+createProcessSuccess p a = createProcessChecked (forceSuccessProcess p) p a
+
+{- Runs createProcess, then an action on its handles, and then
+ - an action on its exit code. -}
+createProcessChecked :: (ProcessHandle -> IO b) -> CreateProcessRunner
+createProcessChecked checker p a = do
+	t@(_, _, _, pid) <- createProcess p
+	r <- a t
+	_ <- checker pid
+	return r
+
+{- Leaves the process running, suitable for lazy streaming.
+ - Note: Zombies will result, and must be waited on. -}
+createBackgroundProcess :: CreateProcessRunner
+createBackgroundProcess p a = a =<< createProcess p
+
+{- Runs a CreateProcessRunner, on a CreateProcess structure, that
+ - is adjusted to pipe only from/to a single StdHandle, and passes
+ - the resulting Handle to an action. -}
+withHandle
+	:: StdHandle
+	-> CreateProcessRunner
+	-> CreateProcess
+	-> (Handle -> IO a)
+	-> IO a
+withHandle h creator p a = creator p' $ a . select
+	where
+		base = p
+			{ std_in = Inherit
+			, std_out = Inherit
+			, std_err = Inherit
+			}
+		(select, p')
+			| h == StdinHandle  =
+				(stdinHandle, base { std_in = CreatePipe })
+			| h == StdoutHandle =
+				(stdoutHandle, base { std_out = CreatePipe })
+			| h == StderrHandle =
+				(stderrHandle, base { std_err = CreatePipe })
+
+{- Like withHandle, but passes (stdin, stdout) handles to the action. -}
+withBothHandles
+	:: CreateProcessRunner
+	-> CreateProcess
+	-> ((Handle, Handle) -> IO a)
+	-> IO a
+withBothHandles creator p a = creator p' $ a . bothHandles
+	where
+		p' = p
+			{ std_in = CreatePipe
 			, std_out = CreatePipe
 			, std_err = Inherit
-			, env = environ
 			}
-	output  <- hGetContentsStrict h
-	hClose h
-	forceSuccessProcess pid cmd args
-	return output
+
+{- Extract a desired handle from createProcess's tuple.
+ - These partial functions are safe as long as createProcess is run
+ - with appropriate parameters to set up the desired handle.
+ - Get it wrong and the runtime crash will always happen, so should be
+ - easily noticed. -}
+type HandleExtractor = (Maybe Handle, Maybe Handle, Maybe Handle, ProcessHandle) -> Handle
+stdinHandle :: HandleExtractor
+stdinHandle (Just h, _, _, _) = h
+stdinHandle _ = error "expected stdinHandle"
+stdoutHandle :: HandleExtractor
+stdoutHandle (_, Just h, _, _) = h
+stdoutHandle _ = error "expected stdoutHandle"
+stderrHandle :: HandleExtractor
+stderrHandle (_, _, Just h, _) = h
+stderrHandle _ = error "expected stderrHandle"
+bothHandles :: (Maybe Handle, Maybe Handle, Maybe Handle, ProcessHandle) -> (Handle, Handle)
+bothHandles (Just hin, Just hout, _, _) = (hin, hout)
+bothHandles _ = error "expected bothHandles"
+
+{- Debugging trace for a CreateProcess. -}
+debugProcess :: CreateProcess -> IO ()
+debugProcess p = do
+	debugM "Utility.Process" $ unwords
+		[ action ++ ":"
+		, showCmd p
+		, maybe "" show (env p)
+		]
+	where
+		action
+			| piped (std_in p) && piped (std_out p) = "chat"
+			| piped (std_in p)                      = "feed"
+			| piped (std_out p)                     = "read"
+			| otherwise                             = "call"
+		piped Inherit = False
+		piped _ = True
+
+{- Shows the command that a CreateProcess will run. -}
+showCmd :: CreateProcess -> String
+showCmd = go . cmdspec
+	where
+		go (ShellCommand s) = s
+		go (RawCommand c ps) = c ++ " " ++ show ps
+
+{- Wrappers for System.Process functions that do debug logging.
+ - 
+ - More could be added, but these are the only ones I usually need.
+ -}
+
+createProcess :: CreateProcess -> IO (Maybe Handle, Maybe Handle, Maybe Handle, ProcessHandle)
+createProcess p = do
+	debugProcess p
+	System.Process.createProcess p
+
+runInteractiveProcess
+	:: FilePath	
+	-> [String]	
+	-> Maybe FilePath	
+	-> Maybe [(String, String)]	
+	-> IO (Handle, Handle, Handle, ProcessHandle)
+runInteractiveProcess f args c e = do
+	debugProcess $ (proc f args)
+			{ std_in = CreatePipe
+			, std_out = CreatePipe
+			, std_err = CreatePipe
+			}
+	System.Process.runInteractiveProcess f args c e
+
+readProcess
+	:: FilePath	
+	-> [String]	
+	-> String	
+	-> IO String
+readProcess f args input = do
+	debugProcess $ (proc f args) { std_out = CreatePipe }
+	System.Process.readProcess f args input
diff --git a/Utility/SafeCommand.hs b/Utility/SafeCommand.hs
index 47280a40b..19dd707b8 100644
--- a/Utility/SafeCommand.hs
+++ b/Utility/SafeCommand.hs
@@ -8,7 +8,8 @@
 module Utility.SafeCommand where
 
 import System.Exit
-import System.Process
+import Utility.Process
+import System.Process (env)
 import Data.String.Utils
 import Control.Applicative