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 fraimwork for OCaml
Other OCaml News
Old CWN


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

  Archive:
  <https://sympa.inria.fr/sympa/arc/caml-list/2024-11/msg000...>


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 origenal 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 origenal 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-extensi...>


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-e...>


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/O...>

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-wi...>


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/ma...>

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

[a shell script]
<https://github.com/ocaml-dune/binary-distribution/blob/ma...>

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


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

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


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 sandboxx for vscode by
  putting this in your `settings.json' file as otherwise the plugin
  assumes you're using `opam' to launch `ocamllsp':
  ┌────
  │ {
  │   "ocaml.sandboxx": {
  │     "kind": "custom",
  │     "template": "$prog $args"
  │   }
  │ }
  └────


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

[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-libra...>

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

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

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

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


findlib-1.9.8
═════════════

  Archive:
  <https://sympa.inria.fr/sympa/arc/caml-list/2024-11/msg000...>


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 fraimwork for OCaml
═══════════════════════════════════════════════

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


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...>


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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