Apparently there's quite a bit of demand for a fix.

@dcoutts What happened to the IO code rewrite you mentioned? It would be interesting to see how you solved this issue!

since it is slightly different behaviour I'll probably include the IO actions in a new module (and eventually deprecate the existing ones).

Yeah. I suspect that simply changing the behaviour of getLine and hGetLine could possibly cause some subtle bugs in existing code.

So how about adding variants like getLineCrossPlatform and hGetLineCrossPlatform that respect the handle's newline settings?

For reference, here's the relevant code:

bytestring/Data/ByteString.hs

Lines 1618 to 1668 in 39ad965

    
           -- | Read a line from stdin. 
        
           getLine :: IO ByteString 
        
           getLine = hGetLine stdin 
        
           -- | Read a line from a handle 
        
           hGetLine :: Handle -> IO ByteString 
        
           hGetLine h = 
        
             wantReadableHandle_ "Data.ByteString.hGetLine" h $ 
        
               \ h_@Handle__{haByteBuffer} -> do 
        
                 flushCharReadBuffer h_ 
        
                 buf <- readIORef haByteBuffer 
        
                 if isEmptyBuffer buf 
        
                    then fill h_ buf 0 [] 
        
                    else haveBuf h_ buf 0 [] 
        
            where 
        
             fill h_@Handle__{haByteBuffer,haDevice} buf !len xss = do 
        
               (r,buf') <- Buffered.fillReadBuffer haDevice buf 
        
               if r == 0 
        
                  then do writeIORef haByteBuffer buf{ bufR=0, bufL=0 } 
        
                          if len > 0 
        
                             then mkBigPS len xss 
        
                             else ioe_EOF 
        
                  else haveBuf h_ buf' len xss 
        
             haveBuf h_@Handle__{haByteBuffer} 
        
                     buf@Buffer{ bufRaw=raw, bufR=w, bufL=r } 
        
                     len xss = 
        
               do 
        
                   off <- findEOL r w raw 
        
                   let new_len = len + off - r 
        
                   xs <- mkPS raw r off 
        
                 -- if eol == True, then off is the offset of the '\n' 
        
                 -- otherwise off == w and the buffer is now empty. 
        
                   if off /= w 
        
                       then do if w == off + 1 
        
                                       then writeIORef haByteBuffer buf{ bufL=0, bufR=0 } 
        
                                       else writeIORef haByteBuffer buf{ bufL = off + 1 } 
        
                               mkBigPS new_len (xs:xss) 
        
                       else fill h_ buf{ bufL=0, bufR=0 } new_len (xs:xss) 
        
             -- find the end-of-line character, if there is one 
        
             findEOL r w raw 
        
                   | r == w = return w 
        
                   | otherwise =  do 
        
                       c <- readWord8Buf raw r 
        
                       if c == fromIntegral (ord '\n') 
        
                           then return r -- NB. not r+1: don't include the '\n' 
        
                           else findEOL (r+1) w raw

	-- \| Read a line from stdin.
	getLine :: IO ByteString
	getLine = hGetLine stdin

	-- \| Read a line from a handle

	hGetLine :: Handle -> IO ByteString
	hGetLine h =
	wantReadableHandle_ "Data.ByteString.hGetLine" h $
	\ h_@Handle__{haByteBuffer} -> do
	flushCharReadBuffer h_
	buf <- readIORef haByteBuffer
	if isEmptyBuffer buf
	then fill h_ buf 0 []
	else haveBuf h_ buf 0 []
	where

	fill h_@Handle__{haByteBuffer,haDevice} buf !len xss = do
	(r,buf') <- Buffered.fillReadBuffer haDevice buf
	if r == 0
	then do writeIORef haByteBuffer buf{ bufR=0, bufL=0 }
	if len > 0
	then mkBigPS len xss
	else ioe_EOF
	else haveBuf h_ buf' len xss

	haveBuf h_@Handle__{haByteBuffer}
	buf@Buffer{ bufRaw=raw, bufR=w, bufL=r }
	len xss =
	do
	off <- findEOL r w raw
	let new_len = len + off - r
	xs <- mkPS raw r off

	-- if eol == True, then off is the offset of the '\n'
	-- otherwise off == w and the buffer is now empty.
	if off /= w
	then do if w == off + 1
	then writeIORef haByteBuffer buf{ bufL=0, bufR=0 }
	else writeIORef haByteBuffer buf{ bufL = off + 1 }
	mkBigPS new_len (xs:xss)
	else fill h_ buf{ bufL=0, bufR=0 } new_len (xs:xss)

	-- find the end-of-line character, if there is one
	findEOL r w raw
	\| r == w = return w
	\| otherwise = do
	c <- readWord8Buf raw r
	if c == fromIntegral (ord '\n')
	then return r -- NB. not r+1: don't include the '\n'
	else findEOL (r+1) w raw

Uh oh!

getLine doesn't honor handle's newline setting #13

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