[Teaching] Getting opam's user-setup working cleanly

[Yaron Minsky]

My apologies.  I just put up a post about all this on the platform
list, so I've now split the discussion.  How about we move the
conversation over there.  I think we probably shouldn't come back to
the teaching list until we've resolved some more of these questions
anyway.

On Fri, Jan 23, 2015 at 10:02 PM, Louis Gesbert
<louis.gesbert at ocamlpro.com> wrote:
> user-setup doesn't handle yet the Mac-specific issue of Emacs load-paths, so that's probably what is bitting you here; I'll port the related code from your .emacs; getting a means to test on these ASAP.
>
>
> On hardcoding the paths, I'm still not certain it is the best option, but I had a few reasons for doing so (open for discussion, obviously, this is still a prototype):
>
> * user-setup configures editors depending on what is installed in the current switch ; it may not make sense in other switches.
>
> * some tools are generally useful (tuareg, ocp-indent) and installing them in one switch should be enough. There is a clear distinction though for compiler-version dependent tools (merlin, ocp-index).
>
> * this is not focused on advanced users with multiple switches, etc. and it makes the configuration simpler to understand and edit.
>
> * this approach is guaranteed to be available for all editors.
>
> The alternatives would be (i) using packages supplied within the editor's ecosystems, when available (see the detailed discussion at [1]), which should clearly handle locations dynamically -- I think that best serves advanced users but has a purpose distinct enough to justify both approaches ; and (ii) dynamically generating configuration at editor run time (like ocp-edit does for emacs: it reads its own configuration and outputs elisp code that is evaluated at run time)
>
> Note that we still hit a consistency issue with this approach if installing user-setup in multiple switches. This also raises the question of handling "global" or "multi-switch" packages in OPAM.
>
>
> On the feature of dynamically adapting to the latest `opam switch` in emacs, it could be achieved by running all external commands through `opam config exec -- <command>`. It doesn't extend to running different elisp files depending on the switch though, and you'd still need to manually update PATH etc. if you're running builds within emacs, similar to `eval $(opam config env)`. I do this using:
>
>     (defun opam-env ()
>       (interactive nil)
>       (dolist (var (car (read-from-string (shell-command-to-string "opam config env --sexp"))))
>         (setenv (car var) (cadr var))))
>
> opam-user-setup will set this statically, locally on caml/tuareg buffers, which may indeed not be the best idea.
>
> Thanks for the feedback, it'll help make this usable quick
> Louis
>
>> - Yaron Minsky, 23/01/2015 20:48 -
>> Hmm.  I'm still not able to get user-setup to work cleanly on my mac,
>> though depext does install now, and I think correctly determines that
>> there are no packages it needs to install.
>>
>> But here are the messages I get from emacs:
>>
>> Loading paren...done
>> Loading tuareg-site-file...done
>> For information about GNU Emacs and the GNU system, type C-h C-a.
>> Making completion list...
>> Starting merlin instance: default (binary=ocamlmerlin).
>> File mode specification error: (file-error "Searching for program" "no
>> such file or directory" "ocamlmerlin")
>>
>> So it can't seem to find merlin.
>>
>> I'm also a little troubled by the hard-coding of paths in the .emacs.
>> Once nice thing about the dot-emacs file I shared with Greg is that it
>> auto-updates where it points on every opam switch, without even
>> needing to restart emacs, I believe.  It would be nice to have this
>> for merlin, though I admit perhaps not with tuareg.
>>
>> I tend to think that until we get this sorted, teachers should use
>> manually put together dot-emacs files like the ones I emailed out.
>>
>> y
>>
>> On Fri, Jan 23, 2015 at 12:39 AM, Anil Madhavapeddy <anil at recoil.org> wrote:
>> > Fixed; there was a minor typo in the `opam` file for the package;
>> > https://github.com/ocaml/opam-repository/pull/3441
>> >
>> > -a
>> >
>> >> On 23 Jan 2015, at 04:33, Yaron Minsky <yminsky at janestreet.com> wrote:
>> >>
>> >> Also, I can't seem to install depext, but the reason doesn't make sense:
>> >>
>> >> Kalessin:~ yminsky2$ opam install depext
>> >> [ERROR] depext is not available because your system doesn't comply
>> >> with opam-version >= "4.02".
>> >> Kalessin:~ yminsky2$ opam --version
>> >> 1.2.0
>> >>
>> >> I'm running the latest opam available from homebrew.
>> >>
>> >> y
>> >>
>> >> On Thu, Jan 22, 2015 at 10:21 PM, Yaron Minsky <yminsky at janestreet.com> wrote:
>> >>> Does depext do anything on a mac?  On redhat? Or is it Debian only?
>> >>>
>> >>> On Jan 22, 2015 10:03 PM, "Louis Gesbert" <louis.gesbert at ocamlpro.com>
>> >>> wrote:
>> >>>>
>> >>>> Just released 0.2 which should fix both issues (opam tuareg mode and
>> >>>> stalling with vim)
>> >>>>
>> >>>>> It would be good to know what we have there now.  It seems like a
>> >>>>> minimum should be:
>> >>>>>
>> >>>>> - tuareg
>> >>>>> - merlin
>> >>>>> - ocp-indent
>> >>>>> - utop
>> >>>>>
>> >>>>> all read to go in emacs.  Getting vim and sublime text support would
>> >>>>> be lovely too, but I think less critical.  What does user-setup
>> >>>>> already support?
>> >>>>
>> >>>> Needs more testing, but we do have those ; vim support also, but it's more
>> >>>> lightly tested.
>> >>>> I didn't figure how to configure Sublime yet.
>> >>>>
>> >>>>> Interesting. Concretely, what would would depext do in this context?
>> >>>>> I did a fresh install of a number of packages on my mac, and I didn't
>> >>>>> need much else, but I may have already had the dependencies in place
>> >>>>> via brew.
>> >>>>
>> >>>> Not sure, but you can use `opam depext -l` to simply show the currently
>> >>>> required external packages.
>> >>>>
>> >>>> The one that bites most often on .deb distributions is the lack of m4,
>> >>>> which is required by ocamlfind. It gets much more complicated as soon as you
>> >>>> want to install e.g. gtk stuff, of course (ocaml-top...).
>> >>>>
>> >>>> Best,
>> >>>> Louis
>> >>
>> >