Re: [PATCH] emacs: Use socket instead of port.

[ludo@gnu.org (Ludovic Courtès)]

Alex Kost <alezost@gmail.com> skribis:

> Currently, if you try to run a repl command (for example, "M-x
> guix-installed-packages") in a second Emacs instance, you'll get an
> unfriendly error.  That's because `guix-default-port' is busy already
> (by another Guix REPL), so you either have to change it manually or use
> (setq guix-use-guile-server nil).  So with the attached patch, a socket
> file with a generated name will be used instead of a port, which allows
> you to run as many Emacs instances with Guix REPLs as you want.
>
> Many thanks to Florian for the great idea!

That’s a good idea, indeed.

> There is one small thing though: Guile does not remove socket file after
> exiting from "guile --listen=/tmp/foo" so these dead sockets will stay in
> /tmp dir.  As there is no `comint-exit-hook' or alike, I don't see how a
> socket file can be removed after the REPL is killed.

You could maybe arrange to have Guile run something like:

  (dynamic-wind
    (const #t)
    (lambda ()
      (start-repl))  ;start a new REPL
    (lambda ()
      (false-if-exception (delete-file "/tmp/foo"))))

Not perfect, but I don’t have a better idea.

It may be good to fix it upfront though.  WDYT?

> From d12c0e0909491b5522cf08015c8dbd684d526d51 Mon Sep 17 00:00:00 2001
> From: Alex Kost <alezost@gmail.com>
> Date: Sat, 12 Dec 2015 11:23:03 +0300
> Subject: [PATCH] emacs: Use socket instead of port.
>
> Suggested by Florian Paul Schmidt.
>
> * emacs/guix-backend.el (guix-default-port): Remove.
>   (guix-repl-socket-file-name-function, guix-repl-current-socket): New
>   variables.
>   (guix-repl-socket-file-name): New procedure.
>   (guix-get-guile-program): Take socket as an optional argument.
>   (guix-start-repl-maybe): Adjust accordingly.

Otherwise LGTM.

Thanks,
Ludo’.