[cwn] Attn: Development Editor, Latest OCaml Weekly News
Alan Schmitt
alan.schmitt at polytechnique.org
Tue Mar 14 02:52:15 PDT 2023
Hello
Here is the latest OCaml Weekly News, for the week of March 07 to 14,
2023.
Table of Contents
─────────────────
My experience contributing to the LLVM bindings
Which binding should i use for sqlite , for mariadb and for postgresql
Monday, 6th March - Outreachy Intern Presentation (Dec ’22 Round)
First release of ppx_subliner, a ppx deriver and rewriter for Cmldliner sub-command
Cross-compiling for Embedded arm32 Target (RP2040 / Cortex-M0+)
VOCaml: add and remove type annotations in VS Code
Sunsetting opam-repository-mingw
Outreachy Summer 2023
VS Code extension Alcotest Test Explorer 0.4.0
Old CWN
My experience contributing to the LLVM bindings
═══════════════════════════════════════════════
Archive:
<https://discuss.ocaml.org/t/my-experience-contributing-to-the-llvm-bindings/11599/1>
alan announced
──────────────
Over the past few months, I’ve been contributing patches to the LLVM
bindings. In particular, I ported the bindings to OCaml 5, which
involved removing naked pointers. I wrote about what I learned [here].
[here] <https://alan-j-hu.github.io/writing/llvm-ocaml.html>
Which binding should i use for sqlite , for mariadb and for postgresql
══════════════════════════════════════════════════════════════════════
Archive:
<https://discuss.ocaml.org/t/which-binding-should-i-use-for-sqlite-for-mariadb-for-postgresql/11605/2>
Alain De Vos asked and Nicolas Ojeda Bar replied
────────────────────────────────────────────────
Which binding should i use for sqlite , for mariadb & for
postgresql ?
At LexiFi we have used <https://github.com/mmottl/postgresql-ocaml>
for PostgreSQL and <https://github.com/mmottl/sqlite3-ocaml> for
SQLite for a long time and found them solid.
Kim Nguyễn also replied
───────────────────────
If you are looking for a unified API, there is [Caqti]. It uses the
lower level bindings mentioned by @nojb (and also supports MariaDB
using [mariadb-ocaml]. It feels like the “jdbc for OCaml” but with
much more!
It provides three high-level API, either a standard blocking
interface, or asynchronous with Lwt or asynchronous with Janestreet’s
Async).
[Caqti] <https://github.com/paurkedal/ocaml-caqti>
[mariadb-ocaml] <https://github.com/andrenth/ocaml-mariadb>
Frédéric Loyer then added
─────────────────────────
Caqti is nice and can be completed nicely with ppx_rapper which
transforms a commented SQL string into a typed wrapper.
See <https://github.com/roddyyaga/ppx_rapper>
Monday, 6th March - Outreachy Intern Presentation (Dec ’22 Round)
═════════════════════════════════════════════════════════════════
Archive:
<https://discuss.ocaml.org/t/monday-6th-march-outreachy-intern-presentation-dec-22-round/11564/5>
Patrick Ferris announced
────────────────────────
The presentation is now online:
<https://watch.ocaml.org/w/pQSAfZ9kDSsSnr8Bxzocn3>
Thank you @Prisca for the talk and everybody for joining live. We took
this opportunity to reupload everything to the OCaml Outreachy channel
under the `bactrian' user:
<https://watch.ocaml.org/c/outreachy_ocaml/videos>
Anil Madhavapeddy asked and Prisca replied
──────────────────────────────────────────
Your slides look great, with lots of nice OCaml/TopoJSON
code fragments; might you consider making them available
online somewhere? Making yourself a homepage, or using
something like Speakerdeck are both good options.
@avsm Thank you very much for the kind words. I just did. This is the
link <https://speakerdeck.com/priceless/presentation>
I noticed you published a release of the library to opam –
you should add yourself to the authors list in
`dune-project', so that you are credited in [the
documentation page for TopoJSON ].
Thank you for pointing that out as well. @patrickferris and I will
correct it.
[the documentation page for TopoJSON ]
<https://ocaml.org/p/topojson/latest>
First release of ppx_subliner, a ppx deriver and rewriter for Cmldliner sub-command
═══════════════════════════════════════════════════════════════════════════════════
Archive:
<https://discuss.ocaml.org/t/ann-first-release-of-ppx-subliner-a-ppx-deriver-and-rewriter-for-cmldliner-sub-command/11610/1>
Boning announced
────────────────
I am very pleased to announce the first release of [`ppx_subliner']!
The package is now available through [OPAM].
I am always a big fan of [`ppx_deriving_cmdliner']. It helps you
construct `Cmdliner.Term.t' from record types and makes writing cli
parsing intuitive and painless. But it lacks the ability to generate
values for sub-command groups and the final `Cmdliner' evaluations.
Therefore, `ppx_subliner' comes to life.
`ppx_subliner' can work with `ppx_deriving_cmdliner' to generate
sub-command groups. You can do so by simply tagging the extension to a
variant type.
┌────
│ type foo = { my_arg : string } [@@deriving cmdliner]
│
│ type params =
│ | Foo of foo
│ | Bar
│ [@@deriving_inline subliner]
│ include
│ sig
│ [@@@ocaml.warning "-32"]
│ val params_cmdliner_group_cmds : (params -> 'a) -> 'a Cmdliner.Cmd.t list
│ end[@@ocaml.doc "@inline"]
│ [@@@end]
└────
It will generate a function which takes in a handle function and
return the sub-command list. Here is a simple handle function.
┌────
│ let handle = function
│ | Foo { my_arg } -> print_endline ("Foo " ^ my_arg)
│ | Bar -> print_endline "Bar"
└────
From here, you either construct the final evaluation manually:
┌────
│ let cmd =
│ let open Cmdliner in
│ let doc = "Some docs" in
│ let info = Cmd.info ~doc "foobar" in
│ Cmd.group info (params_cmdliner_group_cmds handle)
│
│ let () = exit (Cmdliner.eval cmd)
└────
or use the `[%%subliner.cmds]' rewriter, which reuses the setfield
syntax:
┌────
│ (* {eval function}.{type name} <- {function expression> *)
└────
┌────
│ [%%subliner.cmds eval.params <- handle]
│ [@@name "foobar"] [@@version "3.14"]
│ (** Some docs *)
└────
┌────
│ $ foobar.exe foo --my-arg 123
│ Foo 123
└────
Both the deriver and rewriter will respect the OCaml docstring. You
can also use `[@name]', `[@man]', `[@envs]' etc to configure all
aspects of the underlying `Cmdliner.Cmd.info' value.
You can also use different evaluation function and set optional
arguments:
┌────
│ [%%subliner.cmds (eval_result ~catch:false).params <-
│ (function
│ | Foo { my_arg } -> print_endline ("Foo " ^ my_arg) |> Result.ok
│ | Bar -> print_endline "Bar" |> Result.ok)]
└────
Please see more details in the [documentation].
[`ppx_subliner'] <https://github.com/bn-d/ppx_subliner>
[OPAM] <https://opam.ocaml.org/packages/ppx_subliner/>
[`ppx_deriving_cmdliner']
<https://github.com/hammerlab/ppx_deriving_cmdliner>
[documentation] <https://boni.ng/ppx_subliner/ppx_subliner/index.html>
What’s next
╌╌╌╌╌╌╌╌╌╌╌
I want to support inline record and enum as arg in the future, and
maybe replicate some of `ppx_deriving_cmdliner'’s functionality, but
better support for `deriving_inline', lists (ie. `-I liba -I libb'
instead of `-I liba,libb'), positional arguments and more compile time
validation. We shall see.
Hope this is helpful. Happy hacking!
<https://github.com/bn-d/ppx_subliner>
Cross-compiling for Embedded arm32 Target (RP2040 / Cortex-M0+)
═══════════════════════════════════════════════════════════════
Archive:
<https://discuss.ocaml.org/t/cross-compiling-for-embedded-arm32-target-rp2040-cortex-m0/11585/8>
Deep in this thread, Calascibetta Romain said
─────────────────────────────────────────────
Note that you probably should take a look on [gilbraltar] which is a
full OCaml runtime for Rasperry Pi 4 (arm64). We already did several
works on this _ocaml toolchain_, a [“guirlande OS”] or a [music player
OS via Jack].
[gilbraltar] <https://github.com/dinosaure/gilbraltar>
[“guirlande OS”]
<https://twitter.com/Dinoosaure/status/1471128595154231300>
[music player OS via Jack]
<https://tarides.com/blog/2022-10-28-the-mirageos-retreat-a-journey-of-food-cats-and-unikernels#implementing-a-jack-port-driver-or-how-to-make-a-unikernel-sing-bare-metal>
VOCaml: add and remove type annotations in VS Code
══════════════════════════════════════════════════
Archive:
<https://discuss.ocaml.org/t/vocaml-add-and-remove-type-annotations-in-vs-code/11618/1>
Lukasz Stafiniak announced
──────────────────────────
I’m happy to announce [a VS Code extension VOCaml] ([GitHub release])
where I’ll be putting my OCaml coding helpers. Currently, it has three
commands:
• /VOCaml: Add Type Annotations/ inserts type annotations around let
bindings.
• /VOCaml: Remove Type Annotations/ removes type annotations from let
bindings.
• /VOCaml: Visit File from Current Line/ triggers a *Quick Open*
dialog populated with a file and line number retrieved from the line
at cursor position.
VOCaml is a companion to [`ppx_minidebug'], but it can be used for its
own merits. It has some limitations, report issues if you try it!
[a VS Code extension VOCaml]
<https://marketplace.visualstudio.com/items?itemName=lukstafi.vocaml>
[GitHub release] <https://github.com/lukstafi/vocaml/releases/tag/1.0.0>
[`ppx_minidebug'] <https://github.com/lukstafi/ppx_minidebug>
Sunsetting opam-repository-mingw
════════════════════════════════
Archive:
<https://discuss.ocaml.org/t/sunsetting-opam-repository-mingw/11632/1>
David Allsopp announced
───────────────────────
As [previously announced], “opam-repository-mingw” is no longer
receiving updates.
We’re actively working on getting the Windows compiler packages into
[ocaml/opam-repository]. There are two issues which are taking (me) a
little while to finish solving, but more on that further below.
In the gap - of hopefully only a month or so - for this being ready,
there’s is an issue that new releases are of course not available when
opam-repository-mingw is being used with [`ocaml/setup-ocaml at v2']
GitHub actions workflows. I’m hoping here to set out what’s happening,
and what steps you may need to take to keep your GitHub Actions
Windows workflows running smoothly over the next few months.
[previously announced]
<https://fdopen.github.io/opam-repository-mingw/2021/02/26/repo-discontinued>
[ocaml/opam-repository] <https://github.com/ocaml/opam-repository>
[`ocaml/setup-ocaml at v2'] <https://github.com/ocaml/setup-ocaml>
What’s happening right now?
╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌
We’ve updated setup-ocaml to use [ocaml-opam/opam-repository-mingw]
instead of [fdopen/opam-repository-mingw] (see
[ocaml/setup-ocaml#651]). This clone has been augmented with:
• OCaml 4.14.1 packages, in the same style as the 4.14.0 forked
packages (the “pre-compiled” package variants exist, but they’re not
pre-compiled)
• Changes to the constraints for _existing_ packages only
If you’re using setup-ocaml in its default configuration, you should
notice no change except that `4.14.x' builds should now use 4.14.1 and
the initial build will be a little slower as it builds from sources
(GitHub Actions caching will then take over for subsequent runs).
For new releases of packages, it’s necessary to _add_ opam-repository
to the repositories selections for the switches. It’s important that
opam-repository is at a _lower priority_ than opam-repository-mingw
for existing packages, so it’s better to use these lines in your
`ocaml/setup-ocaml at v2' step than to issue `opam repo add --rank=1000'
later:
┌────
│ uses: ocaml/setup-ocaml at v2
│ with:
│ opam-repositories: |
│ opam-repository-mingw: https://github.com/ocaml-opam/opam-repository-mingw.git#sunset
│ default: https://github.com/ocaml/opam-repository.git
└────
[ocaml-opam/opam-repository-mingw]
<https://github.com/ocaml-opam/opam-repository-mingw>
[fdopen/opam-repository-mingw]
<https://github.com/fdopen/opam-repository-mingw>
[ocaml/setup-ocaml#651] <https://github.com/ocaml/setup-ocaml/pull/651>
What do I do when things are broken?
╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌
There’s an issue tracker on [ocaml-opam/opam-repository-mingw], and
this is a very good place to start.
If a version of a package isn’t building, there are three possible
remedies:
• Previous versions of the package may have carried non-upstreamed
patches in opam-repository-mingw.
opam-repository’s policy is not to carry such patches. In this case,
the package actually doesn’t work on Windows.
• opam-repository should be updated to have `os != "win32"' added to
the `available' field for the package
• An issue on the package’s upstream repo should be opened
highlighting the need to upstream patches (or even a pull request
with them!)
• The patches in opam-repository-mingw make changes which may not
necessarily be accepted/acceptable upstream in their current form,
so the issue may be a better starting point than simply taking a
patch and opening a pull request for it (for example, the `utop'
package contains patches which may require further work and review)
• The package relies on environment changes in “OCaml for Windows”.
For example, the Zarith package works in “OCaml for Windows” because
the compiler packages unconditionally set the `CC' environment
variable. This change is both not particularly desirable change to
upstream (it is _very_ confusing, for example, when working on the
compiler itself) and also extremely difficult to upstream, so the
fix here is instead to change the package’s availability with `(os
!= "win32" | os-distribution = "cygwinports")' and constrain away
OCaml 5 on Windows (`"ocaml" {< "5.0" | os != "win32"}')
• Package constraints on _existing packages_ need updating in
ocaml-opam/opam-repository-mingw. For example, the release of ppxlib
0.29 required some existing packages to have upperbounds added.
[ocaml-opam/opam-repository-mingw]
<https://github.com/ocaml-opam/opam-repository-mingw/issues>
What about OCaml 5.0.0?
╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌
OCaml 5.0.0 was released with support for the mingw-w64 port only,
however, there’s a quite major bug which wasn’t caught by OCaml’s
testsuite, but is relatively easily triggered by opam packages. I’ve
[previously announced] how to add OCaml 5 to a workflow. For the time
being, the packages for OCaml 5 aren’t automatically made available.
[previously announced]
<https://discuss.ocaml.org/t/pre-ann-installing-windows-ocaml-5-0-0-in-opam/11150>
What’s next?
╌╌╌╌╌╌╌╌╌╌╌╌
The ultimate goal is to be using an upstream build of `opam.exe' with
ocaml/opam-repository, just as on Unix. Once opam 2.2 is generally
available (we’re aiming for an alpha release at the end of March) and
the compiler packages in opam-repository support the Windows builds,
we will recommend stopping use of opam-repository-mingw completely.
The default in setup-ocaml won’t change straight away, since that
risks breaking existing workflows.
With upstream compiler support, we’ll be able to extend some of the
existing bulk build support already being done for Linux to Windows
and start to close the gap of patches in opam-repository-mingw.
Windows compiler packages
╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌
I mentioned earlier the problems with moving the compiler packages
into opam-repository, and just for general interest this elaborates on
them.
The first issue affects the use of the Visual Studio port (“MSVC”) and
is a consequence of the somewhat strange way that the C compiler is
added to the environment when using the Visual Studio C compiler.
“OCaml for Windows” (as well as Diskuv) use a wrapper command (it’s
`ocaml-env' in “OCaml for Windows” and `with-dkml' in Diskuv). Those
commands are Windows-specific, which is an issue for upstream opam.
There’s an alternate way which sets the environment variables in a
more opam-like way. Doing it that way, though, requires an improvement
to opam’s environment handling which is in opam 2.2, otherwise there’s
an easy risk of “blowing” the environment.
The second issue is selecting the C compiler. On Unix, this is easy
with `ocaml-base-compiler' because there is only one “system” C
compiler. Windows has two ports of OCaml, and the configuration
requires it to be explicitly selected. That requires input from the
user on switch creation for a Windows switch.
“OCaml for Windows” solves this by packaging the Windows compilers
with the variant name appended, just as opam-repository used to, so
`ocaml-variants.4.14.1+mingw64' selects the the mingw-w64 port and
`ocaml-variants.4.14.1+msvc64' selects the MSVC64 port. The problem,
as we already had in opam-repository, is that this adds 4 packages for
each release of OCaml in `ocaml-variants', and leads to a
combinatorial explosion when we start considering flambda and other
relevant compiler options.
opam-repository switched to using the `ocaml-option-' packages to
solve the combinatorial explosion which was already present in
opam-repository. The demonstration repo for OCaml 5 on Windows is
already using an adapted version of this so that `ocaml-option-mingw'
selects the mingw-w64 port (by default 64-bit, with
`ocaml-option-32bit' then selecting the 32-bit port).
This work is all in progress and being tested alongside changes in
opam 2.2 to support the _depext_ experience on Windows. The only
reason that’s not being upstreamed piecemeal is that changes to the
compiler packages in opam-repository trigger switch rebuilds all over
the world, so we don’t want to that until we’re sure that the packages
are correct. The intention is to do this around the time of the alpha
release of opam 2.2, once the work in opam itself has settled down.
Thanks for getting to the end, and happy Windows CI testing!
Outreachy Summer 2023
═════════════════════
Archive: <https://discuss.ocaml.org/t/outreachy-summer-2023/11159/10>
Paul-Elliot announced
─────────────────────
Just wanted to say that I also submitted an OCaml Outreachy project!
The goal of the project is to improve the error reporting in the PPXs
ecosystem. This includes both modifying ppxlib’s behavior when
catching an exception raised by a rewriter; and modify existing PPXs
to better report error (by embedding them inside the AST when
relevant, allowing for both multiple error reporting, and creation of
a partial AST that contains all information that could be created).
VS Code extension Alcotest Test Explorer 0.4.0
══════════════════════════════════════════════
Archive:
<https://discuss.ocaml.org/t/ann-vs-code-extension-alcotest-test-explorer-0-4-0/11636/1>
Roland Csaszar announced
────────────────────────
Thanks to @Muqiu-Han a severe bug has been fixed: an exception raised
by `failwith' wasn’t recognized as failure and the test result had
been set to ’passed’.
Changelog:
Version 0.4.0 (2023-03-10)
╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌
• Mark a test case as failed if a `[FAIL]' tag is present, even if the
actual error message can’t be parsed.
Bugfixes
╌╌╌╌╌╌╌╌
• Make the error parser recognize the exception generated by
`failwith'. (Fix [#1])
[#1]
<https://github.com/Release-Candidate/vscode-ocaml-alcotest-test-adapter/issues/1>
Internal Changes
╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌
• Add test cases to check that the changes actually work.
• Fix typo in issue template.
• Correct the job name in the `release' GitHub workflow.
Old CWN
═══════
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[Alan Schmitt]
[send me a message] <mailto:alan.schmitt at polytechnique.org>
[the archive] <https://alan.petitepomme.net/cwn/>
[RSS feed of the archives] <https://alan.petitepomme.net/cwn/cwn.rss>
[online] <http://lists.idyll.org/listinfo/caml-news-weekly/>
[Alan Schmitt] <https://alan.petitepomme.net/>
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