OCaml Changelog

We're excited to announce the release of Dune-release 2.0.0!

This release brings support for putting your .opam files in a opam/ directory. If your project contains dozens of packages, you'll be able to generate them into the opam/ folder starting with Dune 3.8 using (opam_file_location inside_opam_directory) in your dune-project.

Another notable change is the removal of delegates. Users of dune-release who want to publish their packages to another platform than GitHub can now use the dune-release delegate-info and use the output to build their own publication workflows.

We've released OCaml LSP 1.16.2 with a fix that was introduced in 1.16.1 that prevented users from using preprocessor such as CPPO.

We're thrilled to announce the release of OCaml LSP 1.16.1! 🎉

This release comes with new "Extract local" and "Extract function" code actions to easily refactor your code.

We've also disabled code lenses by default following user feedback. You can follow the discussion on GitHub.

This release is also the first OCaml LSP release to use upstream Merlin. Among other things, this means that it is compatible with all the OCaml versions supported by Merlin: currently OCaml 4.14 and 5.0.0.

We're also releasing numerous bug fixes, including:

• A fix to the integration with Dune RPC on Windows, which, alongside Dune 3.9.0, makes OCaml LSP report Dune errors to the editors with Dune watch mode enabled.
• Minor improvements to the Odoc <-> Markdown conversion to return better function documentation on the editor.

And much more! Read the full changelog for a complete list of improvements and bug fixes.

We're excited to announce the release of Ppxlib 0.30.0! It comes with support for OCaml 5.1, various enhancements, and bug fixes.

For PPX writing, Ast_pattern now offers additional utility functions, while metaquot benefits from improved error reporting.

PPX usage sees better compatibility with OCaml trunk, thanks to the Driver's improved Parsetree version recognition. This allows for compatibility with both trunk and stable OCaml versions concurrently.

Finally, this release enhances Ppxlib's compatibility with ReScript, introducing "ns" and "res" as reserved namespaces.

We've released Dune 3.8.2 with a few bug fixes.

The server toxis where Opam-Repo-CI and OCaml-CI were deployed suffered hardware difficulties yesterday, resulting in BTRFS filesystem corruption and memory issues. These issues are tracked on ocaml/infrastructure#51. Services were restored temporarily using a spare spinning disk, but we continued to see ECC memory issues.

All services have now been redeployed on new ARM64 hardware. We retained the databases for Prometheus, OCaml-CI and Opam-Repo-CI, but unfortunately, older job logs have been lost.

The external URLs for these services are unchanged.

The Grafana dashboards at status.ci3.ocamllabs.io and status.ci.ocamllabs.io have been merged into a single dashboard at status.ci.ocamllabs.io. HTTP redirects are in place for the old addresses.

We've just released a patch version of Dune to fix regressions introduced in Dune 3.8.0.

In particular, we've reverted some cross-compilation improvements that caused build failures when using ppx_runtime_libraries and we'll revisit them in a future version of Dune.

With the progress of the ongoing stabilisation effort for OCaml 5.1.0, I am happy to announce a second alpha release for OCaml 5.1.0.

This second alpha release contains many noteworthy fixes:

• a long-awaited GC fix
• a Windows ABI fix

as announced in the first alpha but also

• a compiler-libs (parsetree) fix
• a type system compatibility enhancement change
• a restored backed for s390x/IBM Z

The full list of changes since the first alpha is available below.

Once most major OCaml tools are updated to the last compiler-libs changes, we will switch to beta releases. Hopefully, this will happen in the upcoming weeks. The progress on stabilising the ecosystem is tracked on the opam readiness for 5.1.0 meta-issue.

Currently, the release is still planned for around July.

If you find any bugs, please report them on OCaml's issue tracker.

If you are interested in the ongoing list of new features and bug fixes, the updated change log for OCaml 5.1.0 is available on GitHub.

Installation Instructions

The base compiler can be installed as an opam switch with the following commands on opam 2.1:

opam update
opam switch create 5.1.0~alpha2

The source code for the alpha is also available at these addresses:

• GitHub
• OCaml archives at Inria

Fine-Tuned Compiler Configuration

If you want to tweak the configuration of the compiler, you can switch to the option variant with:

opam update
opam switch create <switch_name> ocaml-variants.5.1.0~alpha2+options <option_list>

where option_list is a space-separated list of ocaml-option-* packages. For instance, for a flambda and no-flat-float-array switch:

opam switch create 5.1.0~alpha2+flambda+nffa ocaml-variants.5.1.0~alpha2+options ocaml-option-flambda ocaml-option-no-flat-float-array

All available options can be listed with opam search ocaml-option.

Feedback on this post is welcomed on Discuss!

We are pleased to announce the patch release of opam 2.1.5.

This opam release consists of backported bug & security fixes:

• Security issue: fix opam installing packages without checking their checksum when the local cache is corrupted in some case (#5538), you can find more information there.
• Variables are now expanded in build-env (as for setenv) (#5352)
• Correctly handle empty environment variable additions (#5350)
• Skip empty environment variable additions (#5350)
• Fix passing archive-mirrors field from init config file to config (#5315)
• git, hg: Use the full SHA1 revision instead of just the 8 first characters (#5342)

Opam installation instructions (unchanged):

1. From binaries: run

   bash -c "sh <(curl -fsSL https://raw.githubusercontent.com/ocaml/opam/master/shell/install.sh) --version 2.1.5"
   

   or download manually from the Github "Releases" page to your PATH. In this case, don't forget to run opam init --reinit -ni to enable sandboxing if you had version 2.0.0~rc manually installed or to update you sandbox script.

2. From source, using opam:

   opam update; opam install opam-devel
   

   (then copy the opam binary to your PATH as explained, and don't forget to run opam init --reinit -ni to enable sandboxing if you had version 2.0.0~rc manually installed or to update your sandbox script)

3. From source, manually: see the instructions in the README.

We hope you enjoy this new minor version, and remain open to bug reports and suggestions.

We are pleased to announce the release of Merlin 4.9 for OCaml 4.14.1 and 5.0.

This maintenance release brings multiple bug fixes and improvements. In particular we identified and patched an important memory consumption issue that could greatly affect Merlin’s performance in heavily functorized projects.

The dune team is pleased to announce the release of Dune 3.8.0.

It is now available in opam-repository. As usual, it should always be safe to upgrade your dune package: new features and deprecations are only available if you upgrade the language version in your dune-project files.

🌟 Spotlight Features

1. Dune concurrent action

Dune 3.8.0 introduced the new concurrent action. You can now use it instead of the progn action to execute actions concurrently.

For instance:

(rule
(action
  (concurrent
  (write-file A "I am file A.\n")
  (write-file B "I am certainly file B.\n")
  (write-file C "I am most certainly file C.\n"))))

will write to files A, B and C concurrently.

2. Support for .mld files

In Dune 3.7.0, we introduced version 0.3 of the mdx stanza, which came with support for .mld files.

In Dune 3.8.0, .mld files are now supported by default with version 0.4 of the mdx stanza!

Have a look at this diff to see how to migrate your code to the new stanza version.

Due to operational difficulties, opam.ci.ocaml.org has temporarily moved to toxis.caelum.ci.dev. An HTTP redirect is in place. Please do not update your bookmarks.

This issue is being tracked on GitHub ocurrent/opam-repo-ci#220.

check.ocamllabs.io has moved to check.ci.ocaml.org. Furthermore, HTTP connections are now upgraded to HTTPS.

There is an HTTP 301 permanent redirect in place for the old address.

New Ubuntu 23.04 and Fedora 38 distributions have been added to docker base image builder. Following their respective releases:

• Ubuntu 23.04 was released 20 April 2023
• Fedora 38 was released 18 April 2023 These images started building from Apr 25th 2023 and have been pushed to https://hub.docker.com/r/ocaml/opam with a full range of OCaml versions and variants. As always the status of the images can be viewed on images.ci.ocaml.org.

Alongside the Linux updates base images containing OCaml 5.1 have also been published for supported Linux platforms. Following the OCaml 5.1 Alpha release announcement on discuss.ocaml.org. Enjoy and please report any issues on ocurrent/docker-base-images/issues.

Following the release of UTop 2.12.0 a few days ago, we released UTop 2.12.1, a patch release that fixes a regression with unit qualification.

This release also includes an implementation of completion-at-point for Emacs.

UTop 2.12.0 is out with support for the upcoming release of OCaml 5.1!

This release also fixes an issue that prevented users to redefine the () constructor. You can now safely run type t = () of unit and continue using your top-level session.

We're pleased to announce the release of Mdx 2.3.0!

This release comes with support for mld files and changes the parser used by the toplevel, which allows Camlp5's parser to be used with MDX.

🌟 Spotlight Feature

Starting in MDX 2.3.0, you can now execute code blocks in your .mld files! 🎉

As a reminder, .mld files are text files similar to Markdown, but instead of using the Markdown markup language, they use the Ocamldoc markdown language - as is used in .mli files. .mld are typically used to write manuals with odoc.

To run mdx on .mld files, start by enabling mdx in your dune-project:

(using mdx 0.3)

Then list your .mld files in the mdx stanza in your dune:

(mdx
 (files index.mld))

Now if you put a code block in index.mld, it will be executed when running dune test and if dune will suggest to promote the output. For instance, if you run dune test with this index.mld:

Here's an example code block in a [.mld] file:

{[
  # List.map (fun x -> x * x) [(1 + 9); 2; 3; 4];;
]}

dune test will return:

diff --git a/_build/default/index.mld b/_build/default/.mdx/index.mld.corrected
index 337b042..c29bb63 100644
--- a/_build/default/index.mld
+++ b/_build/default/.mdx/index.mld.corrected
@@ -2,5 +2,6 @@ Here's an example code block in a [.mld] file:
 
 {[
   # List.map (fun x -> x * x) [(1 + 9); 2; 3; 4];;
+  - : int list = [100; 4; 9; 16]
 ]}

You can run dune promote to accept the change.

You can see a complete demo of this here.

Now you can keep the code blocks in your manual up-to-date even when your API changes!

Four months after the release of OCaml 5.0.0, the set of new features for the future version 5.1.0 of OCaml has been frozen. We are thus happy to announce the first alpha release for OCaml 5.1.0.

This alpha version is here to help fellow hackers join us early in our bug hunting and opam ecosystem fixing fun (see below for the installation instructions). The progresses on stabilising the ecosystem are tracked on the opam readiness for 5.1.0 meta-issue.

If you find any bugs, please report them on OCaml's issue tracker.

Note that this early alpha version is missing two important fixes for the garbage collector and Windows support. Those fixes will be available before the beta. The full release is expected in July.

If you are interested in the ongoing list of new features and bug fixes, the updated change log for OCaml 5.1.0 is available on GitHub.

Installation Instructions

The base compiler can be installed as an opam switch with the following commands on opam 2.1:

opam update
opam switch create 5.1.0~alpha1

For previous version of opam, the switch creation command line is slightly more verbose:

opam update
opam switch create 5.1.0~alpha1 --repositories=default,beta=git+https://github.com/ocaml/ocaml-beta-repository.git

The source code for the alpha is also available at these addresses:

• GitHub
• OCaml archives at Inria

Fine-Tuned Compiler Configuration

If you want to tweak the configuration of the compiler, you can switch to the option variant with:

opam update
opam switch create <switch_name> ocaml-variants.5.1.0~alpha1+options <option_list>

where option_list is a space separated list of ocaml-option-* packages. For instance, for a flambda and no-flat-float-array switch:

opam switch create 5.1.0~alpha1+flambda+nffa ocaml-variants.5.1.0~alpha1+options ocaml-option-flambda ocaml-option-no-flat-float-array

The command line above is slightly more complicated for opam version anterior to 2.1:

opam update
opam switch create <switch_name> --packages=ocaml-variants.5.1.0~alpha1+options,<option_list> --repositories=default,beta=git+https://github.com/ocaml/ocaml-beta-repository.git

In both cases, all available options can be listed with opam search ocaml-option.

Due to maintenance operations on Tuesday 11th April between 7:30am and 11:00am (UTC+1), the build system will be running at approximately 50% capacity. You may experience some build delays in Opam Repo CI and OCaml CI.

Thank you for your patience and understanding during this time.

We are excited to announce the release of Dune 3.7.1, which brings a few bug fixes from the recent 3.7.0 release:

• Resolved watch mode issue for executables on macOS: We have addressed a problem with the recently introduced watch mode for executables that was causing segmentation faults on macOS. Users can now enjoy a stable watch mode without unexpected crashes on macOS.
• Fixed "Too many links" error on Windows: We have fixed an issue that caused Dune build failures with a "Too many links" error on Windows when using Dune cache.

... and a few more, you can consult the changelog for a full list of bug fixes.

The intention is to retire the ocamllabs.io domain. Therefore any services using the domain will be redirected. From today, the Web UI for Opam Repo CI is available on both opam-ci.ci3.ocamllabs.io and opam.ci.ocaml.org with the service available at both opam-repo-ci.ci3.ocamllabs.io and opam-repo.ci.ocaml.org. In time, the ocamllabs.io sites will issue HTTP 301 permanent redirect messages.

Previously, opam.ci.ocaml.org targetted a web server which issued an HTTP 302 redirect to opam.ci3.ocamllabs.io. This redirection has been removed. opam.ci.ocaml.org points to the actual site.

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@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.

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@v2 step than to issue opam repo add --rank=1000 later:

uses: ocaml/setup-ocaml@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

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.

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.

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!

Discuss this post further on the forums.

Following @avsm post on discuss.ocaml.org, we are pleased to announce that DNS names have now been switched over.

We are moving the opam.ocaml.org 2 servers between hosting providers, and wanted to give everyone clear notice that this happening. Over the next 24-48 hours, if you notice any unexpected changes in the way your opam archives work (for example, in your CI or packaging systems), then please do let us know immediately, either here or in ocaml/infrastructure#19 2.

The reason for the move is to take advantage of Scaleway’s generous sponsorship of ocaml.org, and to use their energy efficient renewable infrastructure 4 for our machines.

This also marks a move to building the opam website via the ocurrent 1 infrastructure, which leads to faster and more reliable updates to the hosted package archives (see here for the service graph and build logs 4). There are also now multiple machines behind the opam.ocaml.org 2 DNS (via round-robin DNS), and this makes it easier for us to publish the archives to a global CDN in the future.

But in the very short term, if something explodes unexpectedly, please do let us know.

We are pleased to announce the release of OCamlFormat 0.25.1! This release contains several bug fixes, changes, and new features.

The library is also available through the ocamlformat-lib package on opam. The ocamlformat package only contains the binary.

We would like to thank all contributors for their valuable contributions to this release. Please see the complete changelog for more details.

We hope you enjoy this release and continue to find OCamlFormat a valuable tool for your OCaml projects. You can download ocamlformat.0.25.1 from the opam repository or GitHub.

Thank you for your support and feedback, and please don't hesitate to reach out if you have any questions or issues.

The OCamlFormat team

🌟 Spotlight Feature

1. New if-then-else and break-cases options

Starting in OCamlFormat 0.25.1, we've also added new values to the if-then-else and break-cases options. Now you can use the vertical value to format these expressions in a more readable and consistent way.

These options are not set by default but you can try them out by customizing your .ocamlformat file as usual.

Here are a few examples:

• if-then-else = vertical

-  let epi = if Option.is_some next then fmt "@\n" else fmt_opt epi in
+  let epi =
+    if Option.is_some next then
+      fmt "@\n"
+    else
+      fmt_opt epi
+  in

-    if tree_depth tree > depth then node_depth_truncate_ depth node
-    else (* already short enough; don't bother truncating *)
+    if tree_depth tree > depth then
+      node_depth_truncate_ depth node
+    else
+      (* already short enough; don't bother truncating *)
      node

• break-cases = vertical

-| Ok (`Version | `Help) -> Stdlib.exit 0
-| Error _ -> Stdlib.exit 1
+| Ok (`Version | `Help) ->
+    Stdlib.exit 0
+| Error _ ->
+    Stdlib.exit 1

-    ~f:(function `Int _ | `Float _ -> true | _ -> false)
+    ~f:(function
+      | `Int _
+      | `Float _ ->
+          true
+      | _ ->
+          false)

2. Formatting .mld files

Formatting .mld files as odoc documentation files is now possible! This will make it much easier to maintain high-quality documentation alongside your OCaml code.

This feature is only available in ocamlformat for now, but keep an eye on the future dune releases to know when dune fmt will be able to format your .mld files!

3. Various improvements and bugfixes

We fixed various issues related to indentation, alignment, and comments positioning.

Here are a few examples:

• More consistent indentation inside a parenthesized expression:

        | [ node ] ->
            ( (if List.mem node ~set:integer_graph.(node)
-              then Has_loop [ numbering.forth.(node) ]
-              else No_loop numbering.forth.(node))
+               then Has_loop [ numbering.forth.(node) ]
+               else No_loop numbering.forth.(node))
            , component_edges.(component) )

    (let open Memo.O in
-    let+ w = Dune_rules.Workspace.workspace () in
-    Dune_engine.Execution_parameters.builtin_default
-    |> Dune_rules.Workspace.update_execution_parameters w);
+     let+ w = Dune_rules.Workspace.workspace () in
+     Dune_engine.Execution_parameters.builtin_default
+     |> Dune_rules.Workspace.update_execution_parameters w);

• More consistent formatting of module expressions:

-  module Sel = (val if is_osx () then (module Mac)
-                    else if Sys.unix then (module Unix)
-                    else (module Fail) : Unix_socket)
+  module Sel =
+    (val if is_osx () then (module Mac)
+         else if Sys.unix then (module Unix)
+         else (module Fail)
+        : Unix_socket)

watch.ocaml.org has been updated to run as a Docker service stack rather than via docker-compose. This change allowed an OCurrent pipeline to monitor the Docker repository and update the image via docker service update when a new version is available.

We have several other services updated via OCurrent: deploy.ci.ocaml.org

In OCurrent, we can create a schedule node that triggers every seven days and invokes a docker pull, yielding the current image SHA. If this has changed, run docker service update with the new image.

  let peertube =
     let weekly = Current_cache.Schedule.v ~valid_for:(Duration.of_day 7) () in
     let image = Cluster.Watch_docker.pull ~schedule:weekly "chocobozzz/peertube:production-bullseye" in
     Cluster.Watch_docker.service ~name:"infra_peertube" ~image ()

The deployment is achieved through an Ansible Playbook. Further details are available here.

The second part of the update was to improve the visibility of the backups for watch.ocaml.org. As noted previously, these use Tarsnap running monthly via CRON.

For this, a new plugin was added to OCurrent called ocurrent_ssh. This plugin allows arbitrary SSH commands to be executed as part of an OCurrent pipeline.

Again using a schedule node, the Current_ssh.run node will be triggered on a 30-day schedule, and the logs for each run will be available on deploy.ci.ocaml.org.

  let monthly = Current_cache.Schedule.v ~valid_for:(Duration.of_day 30) () in
   let tarsnap = Current_ssh.run ~schedule:monthly "watch.ocaml.org" ~key:"tarsnap" (Current.return ["./tarsnap-backup.sh"])

We are pleased to announce the release of Merlin 4.8 for OCaml 4.14.1 and 5.0.

This maintenance release brings multiple bug fixes and improvements to document fetching, jump-to-definition and type-on-hover for records' labels.

The dune team is pleased to announce the release of Dune 3.7.0.

As in the previous announce, here is a changelog split in several parts: changes to the dune executable itself (new commands or options, etc) and changes to the dune language. Most of the changes to the latter are only enabled when you opt-in to the new version by specifying (lang dune 3.7) in the corresponding dune-project file. In other words, it should always be safe to upgrade the dune package.

🌟 Spotlight Features

1. Watch mode for executables

Dune 3.7 now supports watch mode for executables! 🎉

It works just as you'd expect, if you define an executable, you can run it with

dune exec -w my-executable

It will interrupt the process when a file change and re-start the application.

For a practical example of the workflows enabled by watch-mode, check this demo of a live reload for web development:

2. Native Windows Polling

Starting from Dune 3.7, Dune watch mode is now available on Windows!

@yams-yams and @nojb from Lexifi have been working on integrating Windows native polling API with Dune to supplement the support for fswatch, which is unavailable on Windows.

Windows users can now run dune build -w out of the box!

3. Qualified Subdirs

It's quite common to organise your code into subdirectories to separate components. Until now, you could do this by including (include_subdirs unqualified) in your dune files, but this wasn't completely satisfying since all of your modules were available in the top-level. If you wanted to expose modules in subdirectories under another module, you had to create a separate library, which was.. quite the overhead.

Dune 3.7 brings support for the highly-anticipated qualified sub-directories. You can now write (include_subdirs qualified) in your dune file, and modules in your subdirectories will be exposed under a module with the name of the directory.