Stack ghc not working with docker

[sgillis]

I'm trying to run the interpreter using stack-ghci. This works well if I use stack with a locally installed ghc. When I put docker: enable true in my ~/.stack/stack.yaml, stack will use Docker containers for building/running. This is when something goes wrong.

I see a Docker container is being created, and when I execute docker logs <container_name> I see the commands I sent through the *haskell* buffer. But the output never makes it into the buffer.

[gracjan]

Creative approach. Are there any people here that can help with this setup?

[sgillis]

I think I found the source of the problem. The output received from the docker process contains a bunch of special unicode characters (like ^M, ^[).

I managed to get the REPL working by customising haskell-interactive-mode-expr-result. I added some code to remove the extra characters and extra lines returned by Docker. (I know this is terrible code, I just threw something together that worked, since I just started learning Lisp to get this working).

However, I still get errors when I load my source code (even though it actually gets loaded correctly). Also, my solution is not ready to be merged since it would break compatibility with the other ways of running GHCi (not to mention that the code sucks). Could someone give me some pointers how to make this a real solution?

[gracjan]

@sgillis: Were you able to proceed with this further?

[sgillis]

Unfortunately I haven't had a lot of extra time to invest into further investigating this, so no progress.

[shanemikel]

I've confirmed this problem. I'm also getting the extra characters, they are escape sequences, or control chars, I believe for controlling a terminal.

I've managed to intercept the stdout directly from the stack process relay, and it has these chars as well. So it looks like these things are showing up before emacs ever sees the output.

[gracjan]

Great! So we wait till stack/docker people find out what is really going on here.

[shanemikel]

Woops. No, it looks like we don't get the escape sequences if I don't pass -t to docker with my custom container setup (without stack docker support), but I get it when my script uses the result of tty -s to decide whether to pass -t. So it does seem to be something with haskell-mode or emacs itself. Can you think of anything @gracjan (perhaps the emacs functions used to run these commands) that would cause that? I've checked (shell-command "tty -s") in my scratch buffer, and the result is 1 (false) as expected.

[gracjan]

As far as I understand inf-haskell uses terminal emulation while interactive-haskell does not. ttys scare me so I do not really know more.