removed all uses of undefined from code base

It's a code smell, can lead to hard to diagnose error messages.

Assistant/Pairing.hs

@@ -81,6 +81,8 @@ data PairingInProgress = PairingInProgress
 	}
 	deriving (Show)
 
+data AddrClass = IPv4AddrClass | IPv6AddrClass
+
 data SomeAddr = IPv4Addr HostAddress
 {- My Android build of the Network library does not currently have IPV6
  - support. -}

Assistant/Pairing/Network.hs

@@ -33,9 +33,9 @@ pairingPort = 55556
 {- Goal: Reach all hosts on the same network segment.
  - Method: Use same address that avahi uses. Other broadcast addresses seem
  - to not be let through some routers. -}
-multicastAddress :: SomeAddr -> HostName
+multicastAddress :: AddrClass -> HostName
-multicastAddress (IPv4Addr _) = "224.0.0.251"
+multicastAddress IPv4AddrClass = "224.0.0.251"
-multicastAddress (IPv6Addr _) = "ff02::fb"
+multicastAddress IPv6AddrClass = "ff02::fb"
 
 {- Multicasts a message repeatedly on all interfaces, with a 2 second
  - delay between each transmission. The message is repeated forever
@@ -62,7 +62,7 @@ multicastPairMsg repeats secret pairdata stage = go M.empty repeats
 	sendinterface cache i = void $ tryIO $
 		withSocketsDo $ bracket setup cleanup use
 	  where
-		setup = multicastSender (multicastAddress i) pairingPort
+		setup = multicastSender (multicastAddress IPv4AddrClass) pairingPort
 		cleanup (sock, _) = sClose sock -- FIXME does not work
 		use (sock, addr) = do
 			setInterface sock (showAddr i)

Assistant/Threads/Committer.hs

@@ -196,7 +196,7 @@ maxCommitSize :: Int
 maxCommitSize = 5000
 
 {- Decide if now is a good time to make a commit.
- - Note that the list of changes has an undefined order.
+ - Note that the list of changes has a random order.
  -
  - Current strategy: If there have been 10 changes within the past second,
  - a batch activity is taking place, so wait for later.

Assistant/Threads/PairListener.hs

@@ -31,7 +31,7 @@ pairListenerThread urlrenderer = namedThread "PairListener" $ do
   where
 	{- Note this can crash if there's no network interface,
 	 - or only one like lo that doesn't support multicast. -}
-	getsock = multicastReceiver (multicastAddress $ IPv4Addr undefined) pairingPort
+	getsock = multicastReceiver (multicastAddress IPv4AddrClass) pairingPort
 		
 	go reqs cache sock = liftIO (getmsg sock []) >>= \msg -> case readish msg of
 		Nothing -> go reqs cache sock

Assistant/Threads/XMPPPusher.hs

@@ -78,4 +78,5 @@ selectNextPush lastpushedto l = go [] l
 		(Pushing clientid _)
 			| Just clientid /= lastpushedto -> (m, rejected ++ ms)
 		_ -> go (m:rejected) ms
-	go [] [] = undefined
+	go [] [] = error "empty push queue"
+

Command/WebApp.hs

@@ -143,10 +143,10 @@ firstRun :: Maybe HostName -> IO ()
 firstRun listenhost = do
 	checkEnvironmentIO
 	{- Without a repository, we cannot have an Annex monad, so cannot
-	 - get a ThreadState. Using undefined is only safe because the
+	 - get a ThreadState. This is only safe because the
 	 - webapp checks its noAnnex field before accessing the
 	 - threadstate. -}
-	let st = undefined
+	let st = error "annex state not available"
 	{- Get a DaemonStatus without running in the Annex monad. -}
 	dstatus <- atomically . newTMVar =<< newDaemonStatus
 	d <- newAssistantData st dstatus

Crypto.hs

@@ -93,7 +93,7 @@ genSharedCipher highQuality =
 {- Updates an existing Cipher, re-encrypting it to add or remove keyids,
  - depending on whether the first component is True or False. -}
 updateEncryptedCipher :: [(Bool, String)] -> StorableCipher -> IO StorableCipher
-updateEncryptedCipher _ SharedCipher{} = undefined
+updateEncryptedCipher _ SharedCipher{} = error "Cannot update shared cipher"
 updateEncryptedCipher [] encipher = return encipher
 updateEncryptedCipher newkeys encipher@(EncryptedCipher _ variant (KeyIds ks)) = do
 	dropKeys <- listKeyIds [ k | (False, k) <- newkeys ]

Database/Fsck.hs

@@ -55,7 +55,7 @@ Fscked
  -
  - This may fail, if other fsck processes are currently running using the
  - database. Removing the database in that situation would lead to crashes
- - or undefined behavior.
+ - or unknown behavior.
  -}
 newPass :: UUID -> Annex Bool
 newPass u = isJust <$> tryExclusiveLock (gitAnnexFsckDbLock u) go

Git.hs

@@ -60,7 +60,7 @@ repoLocation Repo { location = Url url } = show url
 repoLocation Repo { location = Local { worktree = Just dir } } = dir
 repoLocation Repo { location = Local { gitdir = dir } } = dir
 repoLocation Repo { location = LocalUnknown dir } = dir
-repoLocation Repo { location = Unknown } = undefined
+repoLocation Repo { location = Unknown } = error "unknown repoLocation"
 
 {- Path to a repository. For non-bare, this is the worktree, for bare, 
  - it's the gitdir, and for URL repositories, is the path on the remote
@@ -70,12 +70,12 @@ repoPath Repo { location = Url u } = unEscapeString $ uriPath u
 repoPath Repo { location = Local { worktree = Just d } } = d
 repoPath Repo { location = Local { gitdir = d } } = d
 repoPath Repo { location = LocalUnknown dir } = dir
-repoPath Repo { location = Unknown } = undefined
+repoPath Repo { location = Unknown } = error "unknown repoPath"
 
 {- Path to a local repository's .git directory. -}
 localGitDir :: Repo -> FilePath
 localGitDir Repo { location = Local { gitdir = d } } = d
-localGitDir _ = undefined
+localGitDir _ = error "unknown localGitDir"
 
 {- Some code needs to vary between URL and normal repos,
  - or bare and non-bare, these functions help with that. -}

Git/CatFile.hs

@@ -110,4 +110,4 @@ catTree h treeref = go <$> catObjectDetails h treeref
 	parsemodefile b = 
 		let (modestr, file) = separate (== ' ') (decodeBS b)
 		in (file, readmode modestr)
-	readmode = fst . fromMaybe (0, undefined) . headMaybe . readOct
+	readmode = fromMaybe 0 . fmap fst . headMaybe . readOct

Git/LsFiles.hs

@@ -181,12 +181,13 @@ parseUnmerged s
 	| otherwise = case words metadata of
 		(rawblobtype:rawsha:rawstage:_) -> do
 			stage <- readish rawstage :: Maybe Int
-			unless (stage == 2 || stage == 3) $
+			if stage /= 2 && stage /= 3
-				fail undefined -- skip stage 1
+				then Nothing
-			blobtype <- readBlobType rawblobtype
+				else do
-			sha <- extractSha rawsha
+					blobtype <- readBlobType rawblobtype
-			return $ InternalUnmerged (stage == 2) file
+					sha <- extractSha rawsha
-				(Just blobtype) (Just sha)
+					return $ InternalUnmerged (stage == 2) file
+						(Just blobtype) (Just sha)
 		_ -> Nothing
   where
 	(metadata, file) = separate (== '\t') s

Remote/GCrypt.hs

@@ -397,7 +397,7 @@ getGCryptId fast r gc
 	| Git.repoIsLocal r || Git.repoIsLocalUnknown r = extract <$>
 		liftIO (catchMaybeIO $ Git.Config.read r)
 	| not fast = extract . liftM fst <$> getM (eitherToMaybe <$>)
-		[ Ssh.onRemote r (Git.Config.fromPipe r, return (Left undefined)) "configlist" [] []
+		[ Ssh.onRemote r (Git.Config.fromPipe r, return (Left $ error "configlist failed")) "configlist" [] []
 		, getConfigViaRsync r gc
 		]
 	| otherwise = return (Nothing, r)

Remote/Git.hs

@@ -199,7 +199,7 @@ tryGitConfigRead :: Git.Repo -> Annex Git.Repo
 tryGitConfigRead r 
 	| haveconfig r = return r -- already read
 	| Git.repoIsSsh r = store $ do
-		v <- Ssh.onRemote r (pipedconfig, return (Left undefined)) "configlist" [] []
+		v <- Ssh.onRemote r (pipedconfig, return (Left $ error "configlist failed")) "configlist" [] []
 		case v of
 			Right r'
 				| haveconfig r' -> return r'
@@ -228,9 +228,10 @@ tryGitConfigRead r
 		uo <- Url.getUrlOptions
 		v <- liftIO $ withTmpFile "git-annex.tmp" $ \tmpfile h -> do
 			hClose h
-			ifM (Url.downloadQuiet (Git.repoLocation r ++ "/config") tmpfile uo)
+			let url = Git.repoLocation r ++ "/config"
+			ifM (Url.downloadQuiet url tmpfile uo)
 				( pipedconfig "git" [Param "config", Param "--null", Param "--list", Param "--file", File tmpfile]
-				, return $ Left undefined
+				, return $ Left $ error $ "unable to load config from " ++ url
 				)
 		case v of
 			Left _ -> do

Remote/Helper/Chunked.hs

@@ -72,7 +72,7 @@ chunkKeyStream basek chunksize = ChunkKeyStream $ map mk [1..]
 
 nextChunkKeyStream :: ChunkKeyStream -> (Key, ChunkKeyStream)
 nextChunkKeyStream (ChunkKeyStream (k:l)) = (k, ChunkKeyStream l)
-nextChunkKeyStream (ChunkKeyStream []) = undefined -- stream is infinite!
+nextChunkKeyStream (ChunkKeyStream []) = error "expected infinite ChunkKeyStream"
 
 takeChunkKeyStream :: ChunkCount -> ChunkKeyStream -> [Key]
 takeChunkKeyStream n (ChunkKeyStream l) = genericTake n l

Utility/DirWatcher.hs

@@ -57,7 +57,7 @@ eventsCoalesce = False
 #if (WITH_KQUEUE || WITH_FSEVENTS)
 eventsCoalesce = True
 #else
-eventsCoalesce = undefined
+eventsCoalesce = error "eventsCoalesce not defined"
 #endif
 #endif
 
@@ -78,7 +78,7 @@ closingTracked = True
 #if WITH_KQUEUE
 closingTracked = False
 #else
-closingTracked = undefined
+closingTracked = error "closingTracked not defined"
 #endif
 #endif
 
@@ -93,7 +93,7 @@ modifyTracked = True
 #if WITH_KQUEUE
 modifyTracked = False
 #else
-modifyTracked = undefined
+modifyTracked = error "modifyTracked not defined"
 #endif
 #endif
 
@@ -131,7 +131,7 @@ watchDir dir prune scanevents hooks runstartup =
 #else
 type DirWatcherHandle = ()
 watchDir :: FilePath -> Pruner -> Bool -> WatchHooks -> (IO () -> IO ()) -> IO DirWatcherHandle
-watchDir = undefined
+watchDir = error "watchDir not defined"
 #endif
 #endif
 #endif
@@ -150,7 +150,7 @@ stopWatchDir = FSEvents.eventStreamDestroy
 #if WITH_WIN32NOTIFY
 stopWatchDir = Win32Notify.killWatchManager
 #else
-stopWatchDir = undefined
+stopWatchDir = error "stopWatchDir not defined"
 #endif
 #endif
 #endif

Utility/Directory.hs

@@ -111,7 +111,7 @@ moveFile src dest = tryIO (rename src dest) >>= onrename
 			-- But, mv will move into a directory if
 			-- dest is one, which is not desired.
 			whenM (isdir dest) rethrow
-			viaTmp mv dest undefined
+			viaTmp mv dest ""
 	  where
 		rethrow = throwM e
 		mv tmp _ = do

Utility/FileMode.hs

@@ -124,7 +124,7 @@ withUmask _ a = a
 #endif
 
 combineModes :: [FileMode] -> FileMode
-combineModes [] = undefined
+combineModes [] = 0
 combineModes [m] = m
 combineModes (m:ms) = foldl unionFileModes m ms
 

Utility/Metered.hs

@@ -144,7 +144,7 @@ defaultChunkSize :: Int
 defaultChunkSize = 32 * k - chunkOverhead
   where
 	k = 1024
-	chunkOverhead = 2 * sizeOf (undefined :: Int) -- GHC specific
+	chunkOverhead = 2 * sizeOf (1 :: Int) -- GHC specific
 
 data OutputHandler = OutputHandler
 	{ quietMode :: Bool

Utility/Touch.hsc

@@ -54,8 +54,8 @@ instance Storable TimeSpec where
 	-- use the larger alignment of the two types in the struct
 	alignment _ = max sec_alignment nsec_alignment
 	  where
-		sec_alignment = alignment (undefined::CTime)
+		sec_alignment = alignment (1::CTime)
-		nsec_alignment = alignment (undefined::CLong)
+		nsec_alignment = alignment (1::CLong)
 	sizeOf _ = #{size struct timespec}
 	peek ptr = do
 		sec <- #{peek struct timespec, tv_sec} ptr
@@ -92,7 +92,7 @@ touchBoth file atime mtime follow =
  -}
 
 instance Storable TimeSpec where
-	alignment _ = alignment (undefined::CLong)
+	alignment _ = alignment (1::CLong)
 	sizeOf _ = #{size struct timeval}
 	peek ptr = do
 		sec <- #{peek struct timeval, tv_sec} ptr