[Caml-list] Attn: Development Editor, Latest OCaml Weekly News

Alan Schmitt
2024-11-19T06:52:47Z

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Hello

Here is the latest OCaml Weekly News, for the week of November 12 to 19,
2024.

Table of Contents
─────────────────

Boulder Dash in OCaml
Jane Street OCaml extensions – now with developer tooling!
opam 2.3.0 is out!
Installing Developer Tools with Dune
Dune Developer Preview Updates
First release of cmdlang
findlib-1.9.8
Testo 0.1.0 - a new testing framework for OCaml
Other OCaml News
Old CWN

Boulder Dash in OCaml
═════════════════════

Archive:
<https://sympa.inria.fr/sympa/arc/caml-list/2024-11/msg00007.html>

Andreas Rossberg announced
──────────────────────────

Boulder Dash(*) was my favourite computer game in the 8-bit era, first
released on the Atari 400/800 in 1984. Though I never owned an 8-bit
machine myself, I had friends that I annoyed enough to let me play it
on theirs.

As a homage to its 40th anniversary, I put together a fairly faithful
clone of the original game, implemented in just a few 100 lines of
bare OCaml, with nothing but the homely Graphics library. It should
run on Windows, Mac, and Linux, though I was too lazy to test the
latter.

Features:
• Faithful original physics, graphics, and animations
• Authentic scrolling mechanics combined with dynamic window resizing
• All 20 levels, including intermissions, and 5 difficulties
• Pause-and-go mode for relaxed playing

It is open-source here:

<https://github.com/rossberg/boulder-dash>

Enjoy!

/Andreas

(*) <https://en.wikipedia.org/wiki/Boulder_Dash_(video_game)> "Boulder
Dash" is a trademark of BBG Entertainment

Jane Street OCaml extensions – now with developer tooling!
══════════════════════════════════════════════════════════

Archive:
<https://discuss.ocaml.org/t/ann-jane-street-ocaml-extensions-now-with-developer-tooling/15597/1>

Diana Kalinichenko announced
────────────────────────────

Hi everyone! We've just released a new version of our compiler
extensions, complete with all our packages and support for developer
tooling, including ocamlformat, merlin and ocaml-lsp-server. Get the
install instructions at our [GitHub], and enjoy the experience in your
favorite editor like VSCode, Emacs or Vim.

More documentation coming soon :slight_smile:. Stay tuned for future
releases!

[GitHub]
<https://github.com/janestreet/opam-repository/tree/with-extensions>

opam 2.3.0 is out!
══════════════════

Archive: <https://discuss.ocaml.org/t/ann-opam-2-3-0-is-out/15609/1>

Kate announced
──────────────

Hi everyone,

As mentioned in [our talk at the OCaml Workshop 2024], we decided to
switch to a time-based release cycle (every 6 months), starting with
opam 2.3.

As promised, we are happy to announce the final release of opam 2.3.0.

[our talk at the OCaml Workshop 2024]
<https://icfp24.sigplan.org/details/ocaml-2024-papers/10/Opam-2-2-and-beyond>

What’s new?
╌╌╌╌╌╌╌╌╌╌╌

• When loading a repository, *opam now ignores files in packages’
files/ directories which aren’t listed in the extra-files field* of
the opam file. :warning: If you maintain an opam repository, please
read our [blog post] to make sure your repository stays compatible.
• *Packages requiring an unsupported version of opam are now marked
unavailable*, instead of causing a repository error. This means an
opam repository can now allow smoother upgrade in the future
• *opam list –latests-only*: a new option to list only the latest
versions of packages
• *–verbose-on*: a new option to enable verbose output for specified
package names.
• *opam switch import –deps-only*: a new option to install only the
dependencies of the root packages listed in the opam switch export
file
• *opam switch list-available* no longer displays compilers flagged
with `avoid-version~/~deprecated' unless `--all' is given, meaning
that pre-release or unreleased OCaml packages no longer appear to
be the latest version
• *The builtin-0install solver was improved* and should now be capable
of being your default solver instead of `builtin-mccs+glpk'. If you
wish to give it a try, simply calling `opam option
solver=builtin-0install' (call `opam option solver=' restores the
default)
• Most of the *unhelpful conflict messages were fixed* :flashlight:
• *Fix the internal cache of installed packages*, which was storing
the wrong version of the opam file after a build failure. ([#6213])

Various performance and 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].

[blog post] <https://opam.ocaml.org/blog/opam-2-3-0/>

[#6213] <https://github.com/ocaml/opam/pull/6213>

[release note] <https://github.com/ocaml/opam/releases/tag/2.3.0>

[changelog] <https://github.com/ocaml/opam/blob/2.3.0/CHANGES>

Try it!
╌╌╌╌╌╌╌

The upgrade instructions are unchanged:

For Unix systems
┌────
│ bash -c "sh <(curl -fsSL https://opam.ocaml.org/install.sh)"
└────
or from PowerShell for Windows systems
┌────
│ Invoke-Expression "& { $(Invoke-RestMethod https://opam.ocaml.org/install.ps1) }"
└────
Please report any issues to the [bug-tracker].

[bug-tracker] <https://github.com/ocaml/opam/issues>

Installing Developer Tools with Dune
════════════════════════════════════

Archive:
<https://discuss.ocaml.org/t/installing-developer-tools-with-dune/15612/1>

Steve Sherratt announced
────────────────────────

Dune can install and run developer tools in the context of a
project. This feature is available in the [Dune Developer Preview] and
in the upcoming release of Dune 3.17. As with all of Dune's package
management features, consider this feature to be unstable as its UI
and semantics may change without notice.

The currently supported tools are `ocamllsp' and `ocamlformat'. Dune
has a new command `dune tools exec <TOOL> -- [ARGS]...' which
downloads and installs the given tool, and then runs it with the given
arguments (note the `--' which separates arguments to `dune' from
arguments to the tool). Tools are installed locally to the project, in
its `_build' directory, which makes it easy to use different versions
of a tool in different projects. An unfortunate consequence of
installing tools into `_build' is that for the time being all tools
are uninstalled whenever `dune clean' is run.

Let's see it in action:
┌────
│ $ dune tools exec ocamlformat -- --version
│ Solution for dev-tools.locks/ocamlformat:
│ - ocamlformat.0.26.2+binary-ocaml-5.2.0-built-2024-11-07.0-x86_64-unknown-linux-musl
│ Building ocamlformat.0.26.2+binary-ocaml-5.2.0-built-2024-11-07.0-x86_64-unknown-linux-musl
│ Running 'ocamlformat --version'
│ 0.26.2
└────

[Dune Developer Preview] <https://preview.dune.build/>

Precompiled Binaries
╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌

Note that in the example above, Dune's package solver chose to install
version
`0.26.2+binary-ocaml-5.2.0-built-2024-11-07.0-x86_64-unknown-linux-musl'
of `ocamlformat'. This packages comes from a new [repository of binary
packages] containing pre-built executables for a select few Opam
packages. Dune will search this repository in addition to the default
repositories when solving packages for tools only (if a project has
`ocamlformat' in its dependencies, the binary repository won't be
searched while solving the project's dependencies).

The goal of the binary repository is to reduce the time it takes to
get started working on a new project. Without it, Dune would need to
build `ocamlformat' from source along with all of its dependencies,
which can take several minutes.

For now only a small number of package versions are contained in the
binary repository. To demonstrate, here's what happens if we run `dune
tools exec ocamlformat' in a project with `version=0.26.1' in its
`.ocamlformat' file:
┌────
│ $ dune tools exec ocamlformat -- --version
│ Solution for dev-tools.locks/ocamlformat:
│ - astring.0.8.5
│ - base.v0.17.1
│ - base-bytes.base
│ - base-unix.base
│ - camlp-streams.5.0.1
│ - cmdliner.1.3.0
│ ...
│ - ocamlformat.0.26.1
│ ...
│ Building base-unix.base
│ Building ocaml-base-compiler.5.1.1
│ Building ocaml-config.3
│ Building ocaml.5.1.1
│ Building seq.base
│ Building cmdliner.1.3.0
│ ...
│ Building ocamlformat.0.26.1
│ Running 'ocamlformat --version'
│ 0.26.1
└────

Dune parses `.ocamlformat' to determine which version of `ocamlformat'
to install, and `0.26.1' is not in the binary repo so it needed to be
built from source.

If your project requires a version of a package not available in the
binary repository, or you're on an operating system or architecture
for which no binary version of a package exists, the package will be
built from source instead. Currently the binary repository contains
binaries of `ocamlformat.0.26.2', `ocaml-lsp-server.1.18.0' and
`ocaml-lsp-server.1.19.0' for `x86_64-unknown-linux-musl',
`x86_64-apple-darwin' and `aarch64-apple-darwin'.

Note that Linux binaries are statically linked with muslc so they
should work on all distros regardless of dynamic linker.

[repository of binary packages]
<https://github.com/ocaml-dune/ocaml-binary-packages>

Running `ocamllsp'
╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌

The program `ocamllsp' from the package `ocaml-lsp-server' analyzes
OCaml code and sends information to text editors using the [Language
Server Protocol]. The tool is crucial to OCaml's editor integration
and it has a couple of quirks that are worth mentioning here.

TL;DR: Install Dune with the install script on the [Developer Preview
page] and you'll get an [`ocamllsp' shell script] that will install
and run the correct version of `ocamllsp' for your project.

Firstly the `ocamllsp' executable can only analyze code that has been
compiled with the same version of the OCaml compiler as was used to
compile the `ocamllsp' executable itself. Different versions of the
`ocaml-lsp-server' package are incompatible with some versions of the
OCaml compiler (e.g. `ocaml-lsp-server.1.19.0' must be built with at
least `5.2.0' of the compiler). This means that when Dune is choosing
which version of `ocaml-lsp-server' to install it needs to know which
version of the compiler your project is using. This is only known
after the project has been locked (by running `dune pkg lock'), so
Dune will refuse to install `ocamllsp' in a project that doesn't have
a lock directory or for a project that doesn't depend on the OCaml
compiler.

┌────
│ $ dune tools exec ocamllsp
│ Error: Unable to load the lockdir for the default build context.
│ Hint: Try running 'dune pkg lock'
└────

The `ocaml-lsp-server' packages in the [binary repository] contain
metadata to ensure that the `ocamllsp' executable that gets installed
was built with the same version of the compiler as your project. For
example the `ocaml-lsp-server' package built with `ocaml.5.2.0'
contains this line:

┌────
│ conflicts: "ocaml" {!= "5.2.0"}
└────

This prevents it from being chosen if the project depends on any
version of the compiler other than `5.2.0'.

Another quirk is that `ocamllsp' will try to invoke the binaries
`ocamlformat' and `ocamlformat-rpc', both found in the `ocamlformat'
package. The `ocaml-lsp-server' package doesn't depend on
`ocamlformat' as the specific version of `ocamlformat' needed by a
project is implied by the project's `.ocamlformat' file, which package
managers don't consider when solving dependencies. This means that in
general (whether using Dune or Opam for package management) it's up to
the user to make sure that the correct version of `ocamlformat' is
installed in order to use the formatting features of `ocamllsp'.

Otherwise expect this error in your editor:
┌────
│ Unable to find 'ocamlformat-rpc' binary. Types on hover may not be well-formatted. You need to install either 'ocamlformat' of version > 0.21.0 or, otherwise, 'ocamlformat-rpc' package.
└────

Even if `ocamllsp' and `ocamlformat' are both installed by Dune, if
you run `dune tools exec ocamllsp' you will find that `ocamllsp' still
can't find the `ocamlformat' or `ocamlformat-rpc' executables. This is
because unlike Opam, Dune does not install tools into your `$PATH',
and for the sake of simplicity, the `dune tools exec <TOOL>' command
does not modify the environment of the tool it launches. This can be
fixed by adding
`_build/_private/default/.dev-tool/ocamlformat/ocamlformat/target/bin'
(the directory containing `ocamlformat' and `ocamlformat-rpc' when
`ocamlformat' is installed by dune) to the start of your `$PATH'
variable before running `dune tools exec ocamllsp'. For example
starting `ocamllsp' with the following shell script:

┌────
│ OCAMLFORMAT_TARGET="_build/_private/default/.dev-tool/ocamlformat/ocamlformat/target"
│
│ if [ ! -f $OCAMLFORMAT_TARGET/cookie ]; then
│ # Make sure that the ocamlformat dev tool is installed as it's needed by
│ # ocamllsp. There's currently no command that just installs ocamlformat so
│ # we need to run it and ignore the result.
│ dune tools exec ocamlformat -- --help > /dev/null
│ fi
│
│ # Add ocamlformat to the environment in which ocamllsp runs so ocamllsp can invoke ocamlformat.
│ export PATH="$PWD/$OCAMLFORMAT_TARGET/bin:$PATH"
│
│ # Build and run ocamllsp.
│ dune tools exec ocamllsp -- "$@"
└────

Of course, it's rare to manually start `ocamllsp' directly from your
terminal. It's normally launched by text editors. It would be
impractical to configure your text editor to modify `$PATH' and run a
custom command to start `ocamllsp' via Dune, and doing so would make
it impossible to edit any project that _doesn't_ use Dune for package
management. Instead, the Dune Developer Preview ships with [a shell
script] which installs `ocamlformat' and adds its `bin' directory to
`$PATH' before launching `dune tools exec ocamllsp'. The script is
simply named `ocamllsp', and the Dune Developer Preview install script
adds it to `~/.dune/bin' which should already be in your `$PATH' if
you're using the Developer Preview. The `ocamllsp' script also
attempts to fall back to an Opam-managed installation of `ocamllsp' if
it doesn't detect a Dune lockdir so the same script should work for
non-Dune projects. Because the script is named the same as the
`ocamllsp' executable, most editors don't require special
configuration to run it. See the "Editor Configuration" section of the
[Dune Developer Preview page] for more information about setting up
your editor.

Some parts of the `ocamllsp' shell script may eventually make their
way into Dune itself, but for the time being the shell script is the
recommended way to launch `ocamllsp' for users of the Dune Developer
Preview. The net result is that as long as your project has a
lockfile, the first time you edit some OCaml code in the project Dune
will download and run the appropriate version of `ocamllsp'.

[Language Server Protocol]
<https://microsoft.github.io/language-server-protocol/>

[Developer Preview page] <https://preview.dune.build/>

[`ocamllsp' shell script]
<https://github.com/ocaml-dune/binary-distribution/blob/main/tool-wrappers/ocamllsp>

[binary repository]
<https://github.com/ocaml-dune/ocaml-binary-packages>

[a shell script]
<https://github.com/ocaml-dune/binary-distribution/blob/main/tool-wrappers/ocamllsp>

[Dune Developer Preview page] <https://preview.dune.build/>

Dune Developer Preview Updates
══════════════════════════════

Archive:
<https://discuss.ocaml.org/t/ann-dune-developer-preview-updates/15160/52>

Steve Sherratt announced
────────────────────────

A new version of the [vscode-ocaml-platform] was just released which
fixes a few issues with ocamllsp. You'll probably have to update your
install of the Dune Developer Preview (just rerun the command on [this
page]). You'll need to configure a custom sandbox for vscode by
putting this in your `settings.json' file as otherwise the plugin
assumes you're using `opam' to launch `ocamllsp':
┌────
│ {
│ "ocaml.sandbox": {
│ "kind": "custom",
│ "template": "$prog $args"
│ }
│ }
└────

[vscode-ocaml-platform]
<https://marketplace.visualstudio.com/items?itemName=ocamllabs.ocaml-platform>

[this page] <https://preview.dune.build/>

First release of cmdlang
════════════════════════

Archive:
<https://discuss.ocaml.org/t/first-release-of-cmdlang/15616/1>

Mathieu Barbin announced
────────────────────────

Hi everyone!

A little while ago, I [posted] about [cmdlang], a library for creating
command-line parsers in OCaml.

Today, I am happy to give you an update on this project with the
announcement of an initial release of cmdlang packages to the
opam-repository.

These are very early days for this project. I have started using the
`cmdlang+cmdliner' combination in personal projects, and plan to
experiment with `climate' in the near future. Please feel free to
engage in issues/discussions, etc.

The most recent addition on the project is the development of an
evaluation engine based on `stdlib/arg'.

I'd also like to highlight some examples from the project's
tests. Developing these characterization tests was a fun way to learn
more about the different CLI libraries and their differences:

• Short, long and prefix [flag names].
• Various syntaxes for [named arguments] (`-pVALUE', `-p=VALUE', `-p
VALUE').
• Handling of [negative integers] as named arguments.

If you have ideas for more cases to add (entertaining or otherwise),
I'd love to integrate them into the test suite. Thanks!

Below, you'll find details of the released packages. Happy command
parsing!

*cmdlang* the user facing library to build the commands. It has no
dependencies

*cmdlang-to-cmdliner* translate cmdlang commands to cmdliner

*cmdlang-to-climate* translate cmdlang commands to the newly released
climate (compatibility checked with 0.1.0 & 0.2.0)

*cmdlang-stdlib-runner* an execution engine implemented on top of
stdlib.arg

Thank you to @mseri and the opam-repository maintainers for their
help.

[posted]
<https://discuss.ocaml.org/t/cmdlang-yet-another-cli-library-well-not-really/15258>

[cmdlang] <https://github.com/mbarbin/cmdlang>

[flag names]
<https://github.com/mbarbin/cmdlang/blob/main/test/expect/test__flag.ml>

[named arguments]
<https://github.com/mbarbin/cmdlang/blob/main/test/expect/test__named.ml>

[negative integers]
<https://github.com/mbarbin/cmdlang/blob/main/test/expect/test__negative_int_args.ml>

findlib-1.9.8
═════════════

Archive:
<https://sympa.inria.fr/sympa/arc/caml-list/2024-11/msg00014.html>

Gerd Stolpmann announced
────────────────────────

Hi list,

findlib-1.9.8 is out, fixing a few issues that slipped into 1.9.7.

For manual, download, manuals, etc. see here:

<http://projects.camlcity.org/projects/findlib.html>

An updated OPAM package will follow soon.

Testo 0.1.0 - a new testing framework for OCaml
═══════════════════════════════════════════════

Archive:
<https://discuss.ocaml.org/t/ann-testo-0-1-0-a-new-testing-framework-for-ocaml/15624/1>

Martin Jambon announced
───────────────────────

On this 86th anniversary of the first synthesis of LSD by Albert
Hofmann, it is my pleasure to announce [Testo], a new testing library
for OCaml.

It borrows a lot of ideas from Alcotest and is similar in spirit but
adds a few key features that seemed too difficult to incorporate into
Alcotest. For a gentle introduction, check out our
[tutorial]. Important features include:

• support for many options when creating a test of type `Testo.t';
• capturing stdout or stderr output for comparison against the
expected output aka snapshots;
• reviewing and approving tests without re-running them;
• support for nested categories while keeping the test suite as a flat
list;
• parallel execution using multiprocessing.

This is the first official release of Testo and its interface is
likely to change in minor ways until we release version 1.0.0. We've
been using it internally at Semgrep for about a year and it's been
working well for us.

Happy testing!

[Testo] <https://github.com/semgrep/testo>

[tutorial] <https://semgrep.github.io/testo/tutorial/>

Other OCaml News
════════════════

From the ocaml.org blog
───────────────────────

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

• [The New Conference on the Block: What is FUN OCaml?]

[the ocaml.org blog] <https://ocaml.org/blog/>

[The New Conference on the Block: What is FUN OCaml?]
<https://tarides.com/blog/2024-11-13-the-new-conference-on-the-block-what-is-fun-ocaml>

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 look at [the archive] or the [RSS feed of the
archives].

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

[Alan Schmitt]

[send me a message] <mailto:alan.schmitt@polytechnique.org>

[the archive] <https://alan.petitepomme.net/cwn/>

[RSS feed of the archives] <https://alan.petitepomme.net/cwn/cwn.rss>

[caml-list] <https://sympa.inria.fr/sympa/info/caml-list>

[Alan Schmitt] <https://alan.petitepomme.net/>

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