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

[Alan Schmitt <alan.schmitt@polytechnique.org>]

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Hello

Here is the latest OCaml Weekly News, for the week of June 30 to July
07, 2026.

Table of Contents
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opam-minver 0.2.0 - automatically determine minimum dependency versions
Zanuda – OCaml linter experiment
rpgm-decrypt — a formally-verified RPG Maker asset decryptor in OCaml
menhirformat 0.1.0
Solo5 0.12.0
Landmarks 1.7
Why Ocsigen is staying on Lwt (for now)
Dune 3.24
Old CWN


opam-minver 0.2.0 - automatically determine minimum dependency versions
═══════════════════════════════════════════════════════════════════════

  Archive:
  <https://discuss.ocaml.org/t/ann-opam-minver-0-2-0-automatically-determine-minimum-dependency-versions/18328/1>


onetimerobot announced
──────────────────────

  I have published opam-minver 0.2.0 (previous versions were not
  released to the public). What it does is use a binary search to find
  the minimum passing versions of a project's dependencies listed in its
  opam file and optionally writes them out to the opam file in-place. I
  wrote this because I was working on another project (not yet
  published) and got to the point of listing all the dependencies, and
  realizing I had no idea what versions it was compatible with. This
  tool finds that out automatically.

  It's pretty well polished at this point, and it has a cmdliner
  interface, stores its state in a json file so sessions can be resumed
  if need be, and it also finds the minimum compiler versions and
  handles split OCaml compiler bounds if, for example, a project doesn't
  work specifically with early OCaml 5 versions. This could be used not
  only for new projects, but also to relax version bounds on any project
  where they haven't been determined precisely.

  Homepage and readme is here:
  <https://github.com/luminous-moose/opam-minver>


Zanuda – OCaml linter experiment
════════════════════════════════

  Archive:
  <https://discuss.ocaml.org/t/ann-zanuda-ocaml-linter-experiment/11784/14>


Continuing this thread, Kakadu announced
────────────────────────────────────────

  Zanuda 2.1.0 is merged into opam-repository

  • OCaml 5.5 support
  • Lints could be disabled via `[@@@zanuda "-name"]'
  • Lints represented as ocamlfind packages could be loaded at runtime
    and defined outside zanuda codebase. This modularity for now is
    experimental.


rpgm-decrypt — a formally-verified RPG Maker asset decryptor in OCaml
═════════════════════════════════════════════════════════════════════

  Archive:
  <https://discuss.ocaml.org/t/ann-rpgm-decrypt-a-formally-verified-rpg-maker-asset-decryptor-in-ocaml/18324/1>


LulLaS announced
────────────────

  Hi everyone))) :slightly_smiling_face:

  I'd like to share *rpgm-decrypt*, a small command-line tool that
  decrypts and extracts RPG Maker asset archives (XP / VX / VX Ace via
  `.rgssad' / `.rgss2a' / `.rgss3a', and MV / MZ via the XOR-encrypted
  assets and `.pak' archives).

  It started as a clean-room reimplementation and ended up as an excuse
  to push OCaml's correctness tooling as far as I could on a real
  project:

  • *Gospel* specifications on the pure core (`(*@ ... *)' in the
     ~.mli~s)
  • *Why3 + Z3* deductive proofs of the key derivation, little-endian
    reads and a Zip-Slip path-safety invariant (23/23 goals discharged)
  • *QCheck* property tests (round-trip / invariants) alongside the unit
     suite
  • Coverage-guided *afl-fuzz* of the parsers in CI (0 crashes)
  • *bisect_ppx* coverage + a small directed mutation-testing pass
  • Ships as a single static binary via `dune --profile static'; the
    only external dep is `camlzip' (zlib) for the MZ `.pak' path

  Build/test runs on the native Windows OCaml switch as well as Linux.
  Licensed Apache-2.0.

  Example run:

  ┌────
  │ $ rpgm-decrypt "MyGame" out
  │ scanned=1817 decrypted=1685 passthrough=132 skipped=0 failed=0 formats=[MV=1817]
  └────

  Repo, docs and prebuilt Windows/Linux binaries:

  <https://github.com/rolanfreeman6-png/rpgm-decrypt>

  Feedback on the spec/proof setup especially welcome — it's my first
  serious go at Gospel + Why3, so I'd love to hear how others structure
  that on real code.


menhirformat 0.1.0
══════════════════

  Archive: <https://discuss.ocaml.org/t/ann-menhirformat-0-1-0/18322/1>


Federico announced
──────────────────

  Hello,

  I'm glad to announce the first release of `menhirformat', a command
  line tool that formats and indents Menhir and ocamllex source code. It
  uses the [ocamlformat RPC] to pretty-print the OCaml sections of your
  lexers and parsers; it also tries its best to preserve the original
  location of your comments (still needs work in regard to this
  though!).

  This is a satellite project of my ongoing and considerably larger
  effort to add LSP support to these two OCaml dialects,
  [`menhir-lsp']. The formatting functionality was originally embedded
  into the LSP server to handle document formatting requests, and I
  split it out as a standalone application after [this issue].

  You can try it out with `opam install menhirformat'. The CLI is highly
  inspired by ocamlformat's and takes the file to format as argument,
  e.g. `menhirformat calc.mly'. It exposes a small configuration by
  which your can tweak the formatter's behavior; read on the available
  options with `menhirformat --help'.

  You may also integrate it in your dune project by setting up
  [dialects] for Menhir and ocamllex:

  ┌────
  │ (dialect
  │  (name menhir)
  │  (implementation
  │   (extension mly)
  │   (format
  │    (run menhirformat %{input-file}))))
  │ 
  │ (dialect
  │  (name ocamllex)
  │  (implementation
  │   (extension mll)
  │   (format
  │    (run menhirformat %{input-file}))))
  └────

  Then running `dune build @fmt' will format your project's .mll and
  .mly files and display a diff.

  As someone who can't live without format-on-save in their IDE, I was
  really missing a formatter for Menhir and ocamllex files in the OCaml
  ecosystem. I hope `menhirformat' fills that void.

  I'm interested in opinions about the quality of the output and also in
  suggestions for other customization points of the
  configuration. Please share below or through a GitHub issue!

  • opam page: <https://ocaml.org/p/menhirformat/latest>
  • Source code:
    <https://github.com/dalps/menhir-lsp/tree/main/prettyprint>

  Enjoy!


[ocamlformat RPC] <https://ocaml.org/p/ocamlformat-rpc-lib/latest>

[`menhir-lsp'] <https://github.com/dalps/menhir-lsp>

[this issue] <https://github.com/dalps/menhir-lsp/issues/25>

[dialects]
<https://dune.readthedocs.io/en/latest/reference/dune-project/dialect.html#dialect>


Solo5 0.12.0
════════════

  Archive: <https://discuss.ocaml.org/t/ann-solo5-0-12-0/18320/1>


Hannes Mehnert announced
────────────────────────

  We are delighted to announce the release of [Solo5 0.12.0]. This has
  two distinct features: a new hvt [backend for DragonFlyBSD nvmm],
  thanks to first-time contributor Michael Neumann, and [soft power-off
  of virtio unikernels] - a [long-standing feature request], which makes
  using solo5 e.g. on Google compute much smoother – this was initially
  requested by Michael Bacarella, including draft implementations, and
  [now implemented] and merged by Romain Calascibetta.

  Other noteworthy fixes include that `configure.sh' [now checks for the
  C compiler version] to be at least GCC in version 9 or clang in
  version 10. The `solo5-hvt-debug' crashed since too strict seccomp
  rules were applied (since solo5 0.11.0) - thanks to Felix Solcher for
  opening the [issue], and again Romain Calascibetta for the [fix].

  Awaiting opam-repository merge at
  <https://github.com/ocaml/opam-repository/pull/30182>


[Solo5 0.12.0] <https://github.com/Solo5/solo5/releases/tag/v0.12.0>

[backend for DragonFlyBSD nvmm]
<https://github.com/Solo5/solo5/pull/640>

[soft power-off of virtio unikernels]
<https://github.com/Solo5/solo5/pull/647>

[long-standing feature request]
<https://github.com/Solo5/solo5/issues/499>

[now implemented] <https://github.com/Solo5/solo5/pull/647>

[now checks for the C compiler version]
<https://github.com/Solo5/solo5/pull/645>

[issue] <https://github.com/Solo5/solo5/issues/643>

[fix] <https://github.com/Solo5/solo5/pull/644>


Landmarks 1.7
═════════════

  Archive: <https://discuss.ocaml.org/t/ann-landmarks-1-7/18319/1>


Nicolas Ojeda Bar announced
───────────────────────────

  Dear community,

  We are pleased to announce a new release of /Landmarks/, a simple
  runtime profiler for OCaml.

  <https://github.com/LexiFi/landmarks/releases/tag/v1.7>

  The main novelty in this release is the possibility of defining custom
  backends to generate reports that can be consumed by external
  viewers. An example backend that produces
  <https://www.speedscope.app/> reports is included in a new library
  `landmarks-speedscope'. Custom backends can be defined in external
  libraries without needing to modify `landmarks' itself. This support
  was added by @mjambon.

  Happy profiling!

  Cheers, Nicolas


Why Ocsigen is staying on Lwt (for now)
═══════════════════════════════════════

  Archive:
  <https://discuss.ocaml.org/t/why-ocsigen-is-staying-on-lwt-for-now/18318/1>


Vincent Balat announced
───────────────────────

  Over 2025 we migrated the whole Ocsigen stack (ocsigenserver, Eliom,
  ocsigen-toolkit, ocsigen-start) from Lwt to Eio. The migration
  compiles and the test suite passes. We have nonetheless decided **not
  to release it and to stay on Lwt for now**, and we wrote up why.

  Two obstacles stopped us:

  • *Loss of function coloring.* Under Lwt, a `_ Lwt.t' in a type tells
     you a call may suspend or do I/O. In a multi-tier framework like
     Eliom this is crucial: the *same* shared expression can be a local
     call on the server and a network round-trip on the client. Without
     coloring, nothing at the call site tells you where to put a
     spinner, and reactive combinators (`React' / `map_s') silently lose
     the guarantee that they are pure.
  • *Eio's handler model vs browser events.* On the client, DOM event
     handlers are called directly by the browser with no Eio handler on
     the stack, so any `perform' crashes. The usual workaround
     (`Eio_js.start') defers the body via `setTimeout(0)', which runs
     after event propagation and breaks `preventDefault' /
     `stopPropagation'.

  This is *not* an anti-Eio post. Effects are a major achievement of
  OCaml 5 and we are grateful to the multicore team. We also think the
  monadic style is genuinely fine (with `let*' it is comfortable to
  write), and `Lwt_direct' is there for those who dislike monads.

  Our broader worry is ecosystem unity: very large Lwt codebases exist,
  underfunded projects cannot afford such a migration, and a split would
  hurt a community that is already small. To help, we released
  [`ciao-lwt'] (Lwt-to-Eio migration tools), funded by NLnet through NGI
  Zero Core and Tarides. We would love the effects community's view on
  directions that could unblock us, including improving Lwt itself
  (io_uring, effects, multicore).

  Full write-up:
  <https://ocsigen.org/blog/posts/why-ocsigen-stays-on-lwt-for-now.html>

  Feedback, ideas and constructive disagreement very welcome.


[`ciao-lwt'] <https://github.com/tarides/ciao-lwt>


Dune 3.24
═════════

  Archive: <https://discuss.ocaml.org/t/ann-dune-3-24/18316/1>


Shon announced
──────────────

  The Dune team is pleased to announce [the release of dune 3.24.0].

  Highlights include the following

  • Dune package management now uses the relocatable compiler by
    default, for all supported compiler versions. This brings a massive
    speedup to workspace setup in the many cases where built compiler
    versions can be reused. ([ocaml/dune#14357], [@Alizter])

  • Directory targets are now generally available ([ocaml/dune#14579]),
    allowing tools to produce entire directory trees as targets. See the
    [documentation on directory targets] for details.

  • Path handling has been refined, improving the consistency of paths
    across platforms ([ocaml/dune#14278] and [ocaml/dune#14278]) and
    using a more consistent and disciplined location for `%{bin:NAME}'
    variable expansions ([ocaml/dune#14432]).

  • Path-valued percent forms (`%{bin:...}', `%{dep:...}',
    `%{path:...}', and friends) now expand same-directory paths with a
    leading `./', so that shells like `bash' in `(bash ...)' and
    `(system ...)' actions execute them directly instead of looking them
    up in `PATH' ([ocaml/dune#15156]). This is a breaking change for
    configurations that were handling paths naively, and neglected to
    normalize the representation before using it test fixtures or for
    constructing other strings.

  • The deprecated `lang coq' has been removed, as scheduled, superseded
    by `lang rocq'. See [ocaml/dune#12788] for details.

  See [the full changelog] for all new features and fixes, and for
  attribution to the contributors who made it all possible. Thank you,
  contributors!

  If you encounter a problem with this release, please report it in [our
  issue tracker].


[the release of dune 3.24.0]
<https://github.com/ocaml/dune/releases/tag/3.24.0>

[ocaml/dune#14357] <https://github.com/ocaml/dune/pull/14357>

[@Alizter] <https://github.com/Alizter>

[ocaml/dune#14579] <https://github.com/ocaml/dune/pull/14579>

[documentation on directory targets]
<https://dune.readthedocs.io/en/stable/reference/dune/rule.html#directory-targets>

[ocaml/dune#14278] <https://github.com/ocaml/dune/pull/14278>

[ocaml/dune#14432] <https://github.com/ocaml/dune/pull/14432>

[ocaml/dune#15156] <https://github.com/ocaml/dune/pull/15156>

[ocaml/dune#12788] <https://github.com/ocaml/dune/issues/12788>

[the full changelog] <https://github.com/ocaml/dune/releases/tag/3.24.0>

[our issue tracker] <https://github.com/ocaml/dune/issues>


Old CWN
═══════

  If you happen to miss a CWN, you can [send me a message] and I'll mail
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  [Alan Schmitt]


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


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