#11695: On GHCi prompt the arrow (movement) keys create strange character sequences ---------------------------------+-------------------------------------- Reporter: heisenbug | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 8.1 Resolution: | Keywords: Operating System: Linux | Architecture: x86_64 (amd64) Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | ---------------------------------+-------------------------------------- Comment (by heisenbug): FWIW, I found this in a reddit thread, so it seems to be reproducible: https://www.reddit.com/r/haskell/comments/2jmdcg/ghci_uses_readline/clds4pm -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11695#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#11695: On GHCi prompt the arrow (movement) keys create strange character sequences ---------------------------------+-------------------------------------- Reporter: heisenbug | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 8.1 Resolution: | Keywords: Operating System: Linux | Architecture: x86_64 (amd64) Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | ---------------------------------+-------------------------------------- Comment (by heisenbug): I did some experiments: doing it in an `ssh` session (to the very same machine) from a Windows laptop does not trigger the bug. I should say that the RHEL box is a server, `$DISPLAY` is a `vnc` session on different a login box. So there is more IO triggered on the `ghci` machine than one would assume. I did the same thing (wandering around in a block of "mmmmmm"), with `python` repl. No problems. So it mist be a `ghci` thing: {{{ $ ghci GHCi, version 7.11.20150407: http://www.haskell.org/ghc/ :? for help *Main> mmmmmmmmmmmmmmmmmmmmmmmmmmmmODmmmmmmOCmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmCmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmCmmmmmmmmmmmmmmmmmmmmmOODDmmmOCmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmOCmmmmmmmmmmmmDmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmOCmmCmmm <interactive>:2:1: Not in scope: ?mmmmmmmmmmmmmmmmmmmmmmmmmmmmODmmmmmmOCmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmCmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmCmmmmmmmmmmmmmmmmmmmmmOODDmmmOCmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmOCmmmmmmmmmmmmDmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmOCmmCmmm? *Main> :q Leaving GHCi. $ python Python 2.3.7 (#1, Nov 3 2010, 17:47:44) [GCC 3.4.6] on linux2 Type "help", "copyright", "credits" or "license" for more information.

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mmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm }}}

Maybe this is some improper handling of `EINTR` (or such) ? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11695#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

By any chance are you using tmux or a similar program? If so, check out

#11695: On GHCi prompt the arrow (movement) keys create strange character sequences ---------------------------------+-------------------------------------- Reporter: heisenbug | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 8.1 Resolution: | Keywords: Operating System: Linux | Architecture: x86_64 (amd64) Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | ---------------------------------+-------------------------------------- Comment (by heisenbug): Replying to [comment:4 judahj]: the instructions here (your symptoms sound similar):

https://github.com/judah/haskeline/wiki/UsingTmux

No `tmux`. My terminal is a simple `xterm`. There are 3 computers involved: * a windows laptop visualizing a VNC session (by RealVNC) * a linux machine (say, `hostA`) running `vncserver` * another linux server on which I am `slogin`-ed named `hostB`. `hostB` runs `ghci` and has `export DISPLAY=hostA:2` in effect. So all X visuals are being painted into the `vncserver` session.

Otherwise, can you give a little more information about your setup? - What is the value of $TERM - What terminal program (e.g. xterm) you're using - To try to figure out exactly what's confusing ghci: can you explain

more what "$DISPLAY is a vnc session on a different box" means? I'm not familiar with that kind of setup. Which machine are you actually typing text into, and how is that text being relayed to the server that's actually running ghci? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11695#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#11695: On GHCi prompt the arrow (movement) keys create strange character sequences ---------------------------------+-------------------------------------- Reporter: heisenbug | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 8.1 Resolution: | Keywords: Operating System: Linux | Architecture: x86_64 (amd64) Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | ---------------------------------+-------------------------------------- Comment (by heisenbug): Replying to [comment:6 judahj]:

Thanks for the details. To clarify, what machine are you slogin'd *from* into hostB, is it your laptop or hostA? If your laptop, what Windows program are you using to do the connection?

It is not the laptop. The keystroke/mousing/visualization chain is: {{{ laptop <--vnc--> hostA <--ssh--> hostB }}}

(More details: I'm trying to reason about the chain of events from you

pressing your key to it getting received by gghci as the character sequence "\ESC[A" (or similar). The problem is that ghci (really, haskeline) expects to read those characters in a single block, but in your setup they're arriving separately for some reason.) So `ghci` actually utilizes `haskeline`? I heard something to the contrary before. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11695#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#11695: On GHCi prompt the arrow (movement) keys create strange character sequences ---------------------------------+-------------------------------------- Reporter: heisenbug | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 8.1 Resolution: | Keywords: Operating System: Linux | Architecture: x86_64 (amd64) Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | ---------------------------------+-------------------------------------- Comment (by judahj): Let's try this. Can you please download the file Read.hs from: https://gist.github.com/judah/5c5ad518bb43d235efba4fa8f1e9953a And run (in the same terminal/environment that you have the ghci problem): {{{ ghc Read.hs ./Read }}} Then press some letter keys and some arrow keys, and let me know what the output is? For example, on my terminal: {{{ $ ./Prompt "a" "s" "d" "\ESC[D" "\ESC[B" "\ESC[A" }}} The last three lines are from when I pressed arrow keys. Do you see them split into separate lines (e.g. "\ESC", "[" and "D")? If so, that's the problem we should try to solve. Does the same behavior of Read.hs occur on laptop<-vnc->hostA, or only on laptop<->hostA<->hostB? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11695#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

Let's try this. Can you please download the file Read.hs from: https://gist.github.com/judah/5c5ad518bb43d235efba4fa8f1e9953a

And run (in the same terminal/environment that you have the ghci

{{{ ghc Read.hs ./Read }}}

Then press some letter keys and some arrow keys, and let me know what

For example, on my terminal: {{{ $ ./Prompt "a" "s" "d" "\ESC[D" "\ESC[B" "\ESC[A" }}} The last three lines are from when I pressed arrow keys. Do you see

#11695: On GHCi prompt the arrow (movement) keys create strange character sequences ---------------------------------+-------------------------------------- Reporter: heisenbug | Owner: Type: bug | Status: infoneeded Priority: normal | Milestone: Component: GHCi | Version: 8.1 Resolution: | Keywords: Operating System: Linux | Architecture: x86_64 (amd64) Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | ---------------------------------+-------------------------------------- Comment (by heisenbug): Replying to [comment:9 judahj]: problem): the output is? them split into separate lines (e.g. "\ESC", "[" and "D")? If so, that's the problem we should try to solve. Does the same behavior of Read.hs occur on laptop<-vnc->hostA, or only on laptop<->hostA<->hostB? I see stuff like this: {{{ "\ESC[C" "\ESC[" "C" "\ESC[C" "\ESC[C" "\ESC[C" "\ESC[C" "\ESC[C\ESC[C" "\ESC[C" "\ESC[C" }}} Ha, this looks funny: {{{ "\ESC[B" "\ESC[B" "\ESC[B\ESC[B\ESC[B\ESC[B\ESC[B" "\ESC[B" "\ESC[B" "\ESC[B" "\ESC[B" "\ESC[B" "\ESC[B" "\ESC[B" "\ESC[B\ESC[B\ESC[B" "\ESC[B" "\ESC[B\ESC[B" "\ESC[B\ESC[B" "\ESC[B" "\ESC[B" }}} Above sequences happen when via VNC. Let me test putty... ... completely dull. The strings look like this: {{{ "\ESC[B" "\ESC[B" "\ESC[B" "\ESC[B" "\ESC[B" "\ESC[B" "\ESC[B" "\ESC[B" "\ESC[B" "\ESC[B" "\ESC[B" "\ESC[B" "\ESC[B" "\ESC[B" "\ESC[B" }}} Hope this helps!! -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11695#comment:11 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#11695: On GHCi prompt the arrow (movement) keys create strange character sequences ---------------------------------+-------------------------------------- Reporter: heisenbug | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 8.1 Resolution: | Keywords: Operating System: Linux | Architecture: x86_64 (amd64) Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | ---------------------------------+-------------------------------------- Changes (by heisenbug): * status: infoneeded => new Comment: Looking at my previous comments it appears that the syscall `read` will (sometimes) break up `ESC` sequences (when coming through some `ssh` tunnel?), and `haskeline` chokes on bachelor `ESC`s instead of `read`ing on and combining stuff. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11695#comment:13 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler