Re: [Caml-list] Setting up OPAM in emacs

[Wojciech Meyer <wojciech.meyer@gmail.com>]

Christophe's function hook is probably much better and elegant solution,
but this works for me:

>>
(defun dm-opam-switch-root (ocaml-version opam-root)
  (interactive "sOCaml version: \nsOPAM root: ")
  (let* ((path (if (string-match "\\.opam" (car exec-path)) (cdr exec-path) exec-path))
         (entry
          (replace-regexp-in-string
           "\n" ""
           (shell-command-to-string
            (format "opam switch --root %s %s > /dev/null && opam config env | sed -n 's/^PATH=\\([^:]\\+\\):.*$/\\1/p'" opam-root ocaml-version))))
         (env-path (replace-regexp-in-string "\n" "" (shell-command-to-string (format "opam config env --root %s | sed -n 's/^PATH=\\(.*\\)/\\1/p'" opam-root)))))
    (setq exec-path (cons entry path))
    (setenv "PATH" env-path)))

(defun dm-opam-switch (ocaml-version)
  (interactive "sOCaml version: ")
  (dm-opam-switch-root ocaml-version "~/.opam"))
<<

I wouldn't say myself it's a perfect script, but it works. Note that I
use a lot of shell trickery instead of Emacs buffers, which is probably
not a good idea.

You just say M-x dm-opam-switch, and indicate which version you would
like.

Best,
Wojciech

Christophe TROESTLER <Christophe.Troestler@umons.ac.be> writes:

> On Tue, 28 May 2013 09:59:53 +0400, Ivan Gotovchits wrote:
>>
>> 2. Use «eval `opam env config`» in the begining of a compile-command.
>>    This works fine when you switch compiler, but other commands, such as
>>    «C-c C-s» doesn't use new environment.
>
> I use this for the compilation:
>
>     ;; OPAM compilation — one must update to the current compiler
>     ;; before launching the compilation.
>     (defadvice compile (before compile-opam activate)
>       "Run opam to update environment variables"
>       (set (make-local-variable 'compilation-environment)
> 	   (with-temp-buffer
> 	     (ignore-errors (call-process "opam" nil t nil "config" "-env"))
> 	     (goto-char (point-min))
> 	     (while (re-search-forward "; *export.*$" nil t)
> 	       (replace-match "" nil nil))
> 	     (split-string (buffer-substring 1 (point-max)))
> 	     )))
>
> For the toplevel, I am afraid one needs to restart it.  I guess a
> similar trick is possible to automatically select the right one.
>
> Hope it helps,
> C.