[opam-devel] [Caml-list] Setting up OPAM in emacs

Leo White lpw25 at cam.ac.uk
Wed Jun 19 17:24:58 BST 2013

The development version of OPAM now has a "--sexp" option for "opam
config env". So after the next release putting the following in your
".emacs" file should be sufficient for most users:

  ; Set OPAM environment variables
  (dolist (var (car (read-from-string (shell-command-to-string "opam config env --sexp"))))
    (setenv (car var) (cadr var)))



Anil Madhavapeddy <anil at recoil.org> writes:

> I don't use Emacs, but OPAM has several global command-line options that
> may make your OS^H^Heditor integration easier.
> * --root will set the home directory of OPAM (~/.opam by default)
> * --switch will explicitly run the command under a compiler switch that
>   isn't the default one, but without performing a global switch.
> * "opam config exec" will run the sub-command with the right environment
>   variables set to the selected switch.  So:
>     $ opam config exec "ocamlc -version"
>   will get the version of the current OPAM switch ocaml, irrespective
>   of your PATH settings. (This is what Leo is doing for his interactive
>   shell below, but I'm not sure how this interacts with the rest of 
>   Tuareg).
> I would appreciate an Emacs user summarising best practises here and
> letting me know so that I can include a short summary in Real World OCaml.
> best,
> Anil
> On 15 Jun 2013, at 13:07, Gabriel Scherer <gabriel.scherer at gmail.com> wrote:
>> I don't (want to) understand the details of why opam switches don't
>> work well with Emacs right now, or of any of the proposed solutions.
>> Is there a solution integrated in OPAM by now? If not, is there a
>> consensus on what simple users like me should use to solve the
>> problem? Could you (the thread participants) decide on something, and
>> send that to the OPAM upstream, so that future versions solve this
>> issue?
>> (The immediate problem I observe is that compile-command does not use
>> the OCaml versions I would expect it to, in general defaulting to my
>> system OCaml -- that may depend on the way Emacs is launched. More
>> sophisticated things such as being able to call "opam switch" from
>> inside Emacs are probably secondary needs, and I would be fine with a
>> basic integration not supporting that, and letting people hone their
>> emacs-lisp skills for that.)
>> On Tue, Jun 4, 2013 at 4:55 PM, Leo White <lpw25 at cam.ac.uk> wrote:
>>> My personal solution for Tuareg mode is to put:
>>>  ;; Use OPAM's ocaml
>>>  (setq tuareg-interactive-program "opam config exec ocaml")
>>> in my .emacs.
>>> Regards,
>>> Leo
>>> Wojciech Meyer <wojciech.meyer at gmail.com> writes:
>>>> 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=\\([^:]\\+\\):.*$/\\1/p'" opam-root ocaml-version))))
>>>>         (env-path (replace-regexp-in-string "\n" "" (shell-command-to-string (format "opam config env --root %s | sed -n 's/^PATH=\\(.*\\)/\\1/p'" opam-root)))))
>>>>    (setq exec-path (cons entry path))
>>>>    (setenv "PATH" env-path)))
>>>> (defun dm-opam-switch (ocaml-version)
>>>>  (interactive "sOCaml version: ")
>>>>  (dm-opam-switch-root ocaml-version "~/.opam"))
>>>> <<
>>>> I wouldn't say myself it's a perfect script, but it works. Note that I
>>>> use a lot of shell trickery instead of Emacs buffers, which is probably
>>>> not a good idea.
>>>> You just say M-x dm-opam-switch, and indicate which version you would
>>>> like.
>>>> Best,
>>>> Wojciech
>>>> Christophe TROESTLER <Christophe.Troestler at umons.ac.be> writes:
>>>>> On Tue, 28 May 2013 09:59:53 +0400, Ivan Gotovchits wrote:
>>>>>> 2. Use «eval `opam env config`» in the begining of a compile-command.
>>>>>>   This works fine when you switch compiler, but other commands, such as
>>>>>>   «C-c C-s» doesn't use new environment.
>>>>> I use this for the compilation:
>>>>>    ;; OPAM compilation — one must update to the current compiler
>>>>>    ;; before launching the compilation.
>>>>>    (defadvice compile (before compile-opam activate)
>>>>>      "Run opam to update environment variables"
>>>>>      (set (make-local-variable 'compilation-environment)
>>>>>        (with-temp-buffer
>>>>>          (ignore-errors (call-process "opam" nil t nil "config" "-env"))
>>>>>          (goto-char (point-min))
>>>>>          (while (re-search-forward "; *export.*$" 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.
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