Re: OCaml package `ocaml-zarith` not working / Guix installed `ocamlc` not picking up installed libraries (addendum 2 - using guix profiles)

[Zelphir Kaltstahl <zelphirkaltstahl@posteo.de>]

On 30.12.24 18:53, Zelphir Kaltstahl wrote:
> On 30.12.24 18:50, Zelphir Kaltstahl wrote:
>>
>> Hello Guix users,
>>
>> I am facing a problem trying to use Guix to install Ocaml packages.
>>
>> I was implementing a simple recursive factorial function, as part of learning 
>> the language, and tested what would happen, if I calculated factorial of 100 
>> ... Result: 0. "Ah!" I thought, "all I need to do is get that Zarith package 
>> I have been reading about before, and import that in my code!". So I added it 
>> to my manifest.scm file, which I use for a `guix shell`, and expected the 
>> Ocaml compiler to naturally pick up packages installed via guix, since the 
>> Ocaml compiler ocamlc is also installed using guix. However, it seems this is 
>> dysfunctional currently and ocamlc does not realize that the library is in 
>> fact installed. I am not sure where it is looking for libraries.
>>
>> Here is how to reproduce:
>>
>> ~~~~guix-env/channels.scm~~~~
>> (list (channel
>>          (name 'guix)
>>          (url"https://git.savannah.gnu.org/git/guix.git")
>>          (branch "master")
>>          (commit
>>            "4473f8ae902c2192cab6919363a9101ce9861e45")
>>          (introduction
>>            (make-channel-introduction
>>              "9edb3f66fd807b096b48283debdcddccfea34bad"
>>              (openpgp-fingerprint
>>                "BBB0 2DDF 2CEA F6A8 0D1D  E643 A2A0 6DF2 A33A 54FA")))))
>> ~~~~
>>
>> ~~~~guix-env/manifest.scm~~~~
>> (specifications->manifest
>>   '("ocaml"
>>     "ocaml-utop"
>>     "dune"
>>     ;; "opam"  ; using guix to install packages, should not need opam
>>     "bash"
>>     "ocaml-zarith"))
>> ~~~~
>>
>> ~~~~main.ml~~~~
>> open Z
>>
>> let factorial n =
>>    let rec iter n =
>>      if n < (of_int 2)
>>      then of_int 1
>>      else mul n (iter (sub n (of_int 1)))
>>    in
>>      iter (of_int n)
>>
>>
>> let _ = 5 |> factorial |> to_string |> print_endline
>> let _ = 100 |> factorial |> to_string |> print_endline
>> ~~~~
>>
>> ~~~~command~~~~
>> guix time-machine --channels=guix-env/channels.scm -- shell --check --manifest=guix-env/manifest.scm -- bash -c 'ocamlc -c main.ml -o main.byte'
>>
>> guix shell: checking the environment variables visible from shell '/bin/bash'...
>> guix shell: All is good!  The shell gets correct environment variables.
>> File "main.ml", line 1, characters 5-6:
>> 1 | open Z
>>           ^
>> Error: Unbound module Z
>> ~~~~
>
> I would also like to add, that utop _does_ pick up the library and that in 
> utop I can:
>
> ~~~~in utop~~~~
> #require "zarith";;
> ~~~~
>
> And work with its functions.
>
> So this really seems to be about ocamlc.
>
Update:

I tried using guix profiles, hoping, that with profiles and a predictable path 
(and PATH) things would be different.

Here is my setup.

~~~~guix-env/manifest.scm~~~~
(specifications->manifest
  '("emacs"

    ;; PROGRAMMING LANGUAGE - OCAML
    "ocaml@4.14.1"
    "ocaml-utop"
    "dune"
    ;; "opam"
    "ocaml-zarith"

    ... (more packages) ...
    ))
~~~~

~~~~guix-env/channels.scm~~~~
(list (channel
        (name 'guix)
        (url"https://git.savannah.gnu.org/git/guix.git")
        (branch "master")
        (commit
         "c302b7a5966908b3a5db1ef3ccd3af460b847675")
        (introduction
         (make-channel-introduction
          "9edb3f66fd807b096b48283debdcddccfea34bad"
          (openpgp-fingerprint
           "BBB0 2DDF 2CEA F6A8 0D1D  E643 A2A0 6DF2 A33A 54FA")))))
~~~~

~~~~command creating guix profile~~~~
$ GUIX_PROFILE="/home/user/dev/ocaml/ocaml-examples/book-ocaml-programming/guix-profile"

$ echo $GUIX_PROFILE
/home/xiaolong/dev/ocaml/ocaml-examples/book-ocaml-programming/guix-profile

$ GUIX_PROFILE="${GUIX_PROFILE}" guix time-machine --channels=guix-env/channels.scm -- package --manifest=guix-env/manifest.scm --profile=guix-profile
guix package: warning: Consider running 'guix pull' followed by
'guix package -u' to get up-to-date packages and security updates.

The following packages will be installed:
    ... (more packages) ...
    dune                      3.11.0
    emacs                     29.4
    ... (more packages) ...
    ocaml                     4.14.1
    ocaml-utop                2.10.0
    ocaml-zarith              1.12
    ... (more packages) ...

hint: Consider setting the necessary environment variables by running:

      GUIX_PROFILE="/home/user/dev/ocaml/ocaml-examples/book-ocaml-programming/guix-profile"
      . "$GUIX_PROFILE/etc/profile"

Alternately, see `guix package --search-paths -p "/home/user/dev/ocaml/ocaml-examples/book-ocaml-programming/guix-profile"'.
~~~~

~~~~command activating guix profile
$ GUIX_PROFILE="/home/user/dev/ocaml/ocaml-examples/book-ocaml-programming/guix-profile"

$ . "$GUIX_PROFILE/etc/profile"

$ command -V ocaml
ocaml is /home/user/dev/ocaml/ocaml-examples/book-ocaml-programming/guix-profile/bin/ocaml

$ command -V ocamlc
ocamlc is /home/user/dev/ocaml/ocaml-examples/book-ocaml-programming/guix-profile/bin/ocamlc
~~~~

~~~~command running ocaml after activating guix profile~~~~
$ ocamlc -o ex-006-functions/main2.byte ex-006-functions/main2.ml
File "ex-006-functions/main2.ml", line 1, characters 5-6:
1 | open Z
          ^
Error: Unbound module Z
~~~~

So it even with guix profile it does not work and there is no difference in the 
error when using guix shell and guix profile.

This makes me wonder then, how anyone is using any guix package that is named 
`ocaml-...`. `ocamlc` does not pick them up, so they seem unusable, unless one 
uses REPL workflow with utop. But in my opinion REPL workflow, while nice when 
familiar with it, is still not a replacement for having the compiler work 
correctly with installed libraries.

I am for now at a loss how to proceed, except for postponing the usage of 
libraries not part of the Ocaml distribution entirely. But sooner or later this 
will come up and then I will be screwed.

What I would like to have as a result at the end is a Makefile, that takes care 
of all the guix incantations, so that I don't have to construct long commands by 
hand or must rely on command history (happens that I work on another machine for 
example). This Makefile should simply activate (source) the guix profile, 
compile the code (impossible due to the described issue) and run the compiled file.

Of course I would like to benefit from the reproducible nature of having a guix 
shell or guix profile. That is why I am even doing all this in the first place. 
Any machine with working guix package manager I use, I should be able to run the 
code on in a convenient way, not wanting to setup all the tooling over and over 
again, and being sure, that I will get reproducible results.

Best regards,
Zelphir