OCaml Weekly News

Hello

Here is the latest OCaml Weekly News, for the week of October 15 to 22, 202= 4.

opam 2.3.0~beta1

Archive: https://discuss.ocaml.org/t/ann-opam-2-3-0-beta1/15450/1

Kate announced

We're happy to announce the first beta release of opam 2.3.0.

As we're closing on the final release of opam 2.3.0, we'd be happy for peop= le to test this beta and report any regression.

What's new?

This release consists mostly in regression fixes compared to 2.3.0~alpha1:

Fix a regression where pinning a local source repository containing ini= tialized git submodules would cause a failure when fetching the package. (<= a href=3D"https://github.com/ocaml/opam/issues/5809">#5809)
Fix a regression which would make opam crash on platforms such as OpenB= SD. (#6215)
Fix the internal cache of installed packages, which was storing the wro= ng version of the opam file after a build failure. (#6213)
Fix a regression in lint W59 with local urls that are not archives. (#6218)

A couple of other improvements were made and bugs were fixed. :open_book: You can read our blog post for more information about these changes and more= , and for even more details you can take a look at the release note or the changelog.

Try it!

The upgrade instructions are pretty much the same:

For Unix systems

bash -c "sh <(curl -fsSL https://opam.ocaml.org/install.sh) --version 2.=
3.0~beta1"

or from PowerShell for Windows systems

Invoke-Expression "& { $(Invoke-RestMethod https://opam.ocaml.org/insta=
ll.ps1) } -Version 2.3.0~beta1"

Please report any issues to the bug-tracker.

Dune dev meeting

Archive: https://discuss.ocaml.org/t/ann-dune-dev-meeting/14994/14

Steve Sherratt announced

Notes from today's dune-dev meeting are here

Wildcard expansion on Windows

Archive: https://discuss.ocaml.org/t/wildcard-expansion-on-windows/15461= /1

Benjamin Sigonneau announced

While implementing a small CLI tool, I ran into a somehow undocumented feat= ure of the Ocaml compiler: it automatically expands wildcards before doing = anything else. Which proved to be a problem.

This post serves three different goals:

give some visibility, in case someone else run into this issue in the f= uture
expose a possible workaround
ask the community if there is a better way=E2=84=A2 to solve this

Context

My tool uses Cmdliner for CLI args processing, and needs to ha= ndle basic wildcard processing for one of its options, eg. it should handle= mytool.exe -x *.ml.

This would get expanded to mytool.exe -x a.ml b.ml c.ml which = Cmdliner cannot handle. Under any common Unix shell, this is not a problem:= we just have to escape the star character with eg. mytool.exe -x \*.= ml, have mytool handle the expansion itself and we're all set. So fa= r, so good.

Then came Windows. Whatever I would do, it seemed like there was no way of = preventing that wildcard to be expanded. I learned that on Windows, the cal= ling program was responsible for dealing with wildcards, not the shell. Aft= er some digging, the root cause of this behaviour was found in the ocaml ru= ntime itself, in runtime/main.c:




int main_os(int=
 argc, char_os **argv)
{
#ifdef _WIN32
  /* Expand wildcards and diversions in=
 command line */=

  caml_expand_command_line(&argc, &argv);
#endif

/* [...] */
}




After a bit of history digging, it turns out this behaviour dates back from=
 the very early stages of the Ocaml compiler, see this comm=
it by Xavier Leroy from… 1996!


Workaround



The runtime/main.c file gives a hint on how to work around thi=
s:



Main entry =
point (can be overridden by a user-provided main()
   function that calls =
caml_main() later). */

So the most elegant workaround I could find was to create a copy of the main.c file inside the source tree of mytool and comment out the = call to caml_expand_command_line. Then it was a matter of comp= iling and linking everything altogether. I use dune to compile= mytool.exe, and after a lot of trial-and-error, I found out i= t could handle this very easily with the foreign_stubs stanza:

(executable
 (name mytool)
 (foreign_stubs (language c) (names main))
 ; ...
)

Minimal working example

I opened a Github repository containing a minimal project featuring a custo= m entry point so that command-line arguments expansion does not happen on W= indows.

See: https://git= hub.com/benji-sb/ocaml-windows-argv

Open Questions

The root cause of this issue was introduced almost 30 years ago. How co= me no one on the Internets seem to have run into a similar issue?
Why was this behaviour introduced in the first place? I suspect it may = have make it easier to setup a Windows toolchain back then, but that's just= wild speculation.
Is this behaviour still needed, or could we get rid of it?
Should this be more wildly documented, and if so, where? The ocaml comp= iler docs and the dune docs could probably benefit from a small paragraph o= n how to override the default entry point.

OCamlformat and GitHub actions

Archive: https://discuss.ocaml.org/t/ocamlformat-and-github-actions/154= 64/1

Hannes Mehnert announced

a small announcement for those using OCamlformat in their projects: if you = find the burden on external contributors very high, and always express "ple= ase run ocamlformat on your PR" – we've been in the same boat.

We developed a GitHub action which automatically runs OCamlformat and pushe= s that on the PR. No need for contributors to remember running OCamlformat,= no need for "OCaml-CI" to fail since ocamlformat run diverges.

If you're interested, take a look at https://github.com/rob= ur-coop/mollymawk/blob/main/.github/workflows/format.yml – pleas= e note that we use find . -name \*ml -maxdepth 1 – depe= nding on your project you may be able to run dune bu @fmt --auto (or need a slightly different find to look deeper or also f= or mli files).




Happy to share this action which turned out to be tremendously useful for s=
ome of our projects.







New vs. Old OCaml Academic Users Page Survey


Archive: https://discuss.ocaml.org/t/new-vs-old-ocaml-acad=
emic-users-page-survey/15484/1




Claire Vandenberghe announced


We've recently redesigned the OCaml Academic Users page and would lo=
ve to get your feedback to ensure it=E2=80=99s as helpful as possibl=
e. You can view both versions here:



New page: ocaml.org/academ=
ic-users
Old page: staging.=
ocaml.org/academic-users



As a teacher, student expert or beginner developer using OCaml, we=E2=80=99=
d greatly appreciate your insights! Participate in the survey here: https://docs.google.com/forms/d/e/1FAIpQLSfc9qPR16deJ6V=
eVmXGXPVO4e3wZ9ZVIYiWrS4f1RZsqcXxwQ/viewform?usp=3Dsf_link  or we can d=
iscuss this topic below :)



Do you find the new page more useful and relevant for your academic needs c=
ompared to the old one? If so, why?



Is there any information missing or anything you=E2=80=99d suggest improvin=
g on the new page?



Your feedback is incredibly valuable to us as we work to improve the experi=
ence for the OCaml community.



Thank you in advance!









New vs. Old OCaml Industrial Users Page


Archive: https://discuss.ocaml.org/t/new-vs-old-ocaml-industria=
l-users-page/15485/1




Claire Vandenberghe announced


We've recently redesigned the OCaml Industrial Users pages and would=
 love to get your feedback to ensure it=E2=80=99s as helpful as poss=
ible. You can view both versions here:



New: https://ocaml.org/i=
ndustrial-users
Old: https://sta=
ging.ocaml.org/industrial-users



As an expert or beginner developer using OCaml, we=E2=80=99d greatly apprec=
iate your insights! You can also participate to the survey here: https://forms.gle/C7czFt36m7bx4fLt8 or we can discuss this topic below :)



Do you find the new page more useful and relevant for industrial needs comp=
ared to the old one? If so, why?



Is there any information missing or anything you=E2=80=99d suggest improvin=
g on the new page?



Your feedback is incredibly valuable to us as we work to improve the experi=
ence for the OCaml community.



Thank you in advance!









Eliom 11 and Ocsigen Start 7


Archive: https://discuss.ocaml.org/t/ann-eliom-11-and-ocsigen-start-7=
/15487/1




Vincent Balat announced


Eliom 11 and Ocsigen Start 7 have been released a few weeks ago.
These versions follow the recent release of Ocsigen Server 6 and leverage i=
ts new configuration API to make it easier to use it as a library, without =
a configuration file.



Here is an example of a simple OCaml app generating a Web page from server =
side (and serving static pages from directory "local/var/www/mysite"<=
/code>):


let f _ () =3D
  Lwt.return
    Eliom_content.Html.F.(html (head=
 (title (txt "")) [])
                               (body [h1 [txt "Hello"]]))

let myservice =3D
  Eliom_service.create
    ~path:(Eliom_service.Path [])
    ~meth:(Eliom_service.Get Eliom_parameter.any)
    ()

let () =3D Eliom_registration.Html.register ~service:myservice f

let () =3D Ocsigen_server.start=20
    [ Ocsigen_server.host
       [ Staticmod.run ~dir:"local/var=
/www/mysite" ()
       ; Eliom.run () ] ]




To use it, just install Eliom and your favorite version of Ocipersist, then=
 create a new Dune project:

opam install ocsipersist-sqlite-config eliom
dune init project mysite



Put the code above in file bin/mysite.ml



Update file bin/dune:

(executable
 (public_name mysite)
 (name main)
 (libraries
  ocsigenserver
  ocsigenserver.ext.staticmod
  ocsipersist-sqlite
  eliom.server))



Build and execute:

dune exec mysite



Open URL http://localhost:8080/.




Ocsigen Start's application template has been updated to support both the u=
se as an executable or as a library (lynked dynamically from the server's c=
onfig file).



Links:


Ocsigen
Github









Other OCaml News



From the ocaml.org blog


Here are links from many OCaml blogs aggregated at the ocaml.org blog.



Developer education at Jane Street
Dune Developer P=
review: Installing The OCaml Compiler With Dune Package Management
Upcoming OCaml Events









Old CWN


If you happen to miss a CWN, you can send me a message and I'll mail it to you, or go take a loo=
k at the archive or the <=
a href=3D"https://alan.petitepomme.net/cwn/cwn.rss">RSS feed of the archive=
s.



If you also wish to receive it every week by mail, you may subscribe to the=
 caml-list.




Alan Schmitt

OCaml Weekly News

Table of Contents

opam 2.3.0~beta1

Kate announced

What's new?

Try it!

Dune dev meeting

Steve Sherratt announced

Wildcard expansion on Windows

Benjamin Sigonneau announced

Context

Workaround

Minimal working example

Open Questions

OCamlformat and GitHub actions

Hannes Mehnert announced

New vs. Old OCaml Academic Users Page Survey

Claire Vandenberghe announced

New vs. Old OCaml Industrial Users Page

Claire Vandenberghe announced

Eliom 11 and Ocsigen Start 7

Vincent Balat announced

Other OCaml News

From the ocaml.org blog

Old CWN