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Here is the latest OCaml Weekly News, for the week of March 26 to April 02, 2024.

Table of Contents

Odoc 3.0 planning

Jon Ludlam announced

For many years we've had a team here at Tarides working away on Odoc, quietly adding new features, fixing bugs, speeding things up and generally enabling OCaml package mantainers to write good documentation. Up until recently, those improvements have mostly been incremental, but with the recent addition of some larger new features like search and source rendering we've found we need to think a bit more broadly and consider how these changes will fit into the larger ecosystem. We're also thinking of how to extend the abilities of Odoc to handle more structure in the documentation, with better support for images, an improved sidebar, and a better ability to link to the docs of other packages.

We've therefore started the process that's going to lead to Odoc 3.0, which will involve not only work on odoc itself, but also on ocaml.org, the documentation pipeline that produces the docs for ocaml.org, dune, and odig. It's being done incrementally, so we've started with the core issues of how to structure your docs, how to do references both within the docs and across packages, what the output file structure will look like and how the breadcrumbs will reflect that. What we've posted so far is by no means the final version, and we'd love to get feedback on the suggestions we've got so far. Getting this right is surprisingly complicated, so the more people we have thinking about it, the better our chances of success!

So if you're interested in writing or reading docs, I encourage you to head on over to the discussion we've just started on ocaml/odoc and join in the conversation!

OCaml Platform Newsletter: February 2024

Thibaut Mattio announced

Welcome to the tenth edition of the OCaml Platform newsletter!

In this February 2024 edition, we are excited to bring you the latest on the OCaml Platform, continuing our tradition of highlighting recent developments as seen in previous editions. To understand the direction we're headed, especially regarding development workflows and user experience improvements, check out our roadmap.



[Dune] Exploring Package Management in Dune (W4)

Contributed by: @rgrinberg (Tarides), @Leonidas-from-XIV (Tarides), @gridbugs (Tarides), @kit-ty-kate (Tarides), @Alizter

Why: Unify OCaml tooling under a single command line for all development workflows. This addresses one of the most important pain points reported by the community.

What: Prototyping the integration of package management into Dune using opam as a library. We're introducing a dune pkg lock command to generate a lock file and enhancing dune build to handle dependencies in the lock file. More details in the Dune RFC.


  • One of the main remaining blockers to make Dune package management usable in real world project is to make some of the low level dependencies, notably OCamlFind and the OCaml compiler, relocatable. – ocaml/ocamlfind#72
  • We experimented with a Coq-platform patch to make OCamlFind relocatable, but we faced issues with packages using topkg due to ocamlbuild build failures. This led to identifying an error with directory symlink handling in Dune ocaml/dune#9873, ocaml/dune#9937
  • To track the buildability of opam packages with Dune package management, we worked on a GitHub action that effectively provides us with a dashboard of opam packages coverage on a select set of packages. The repository is available at gridbugs/dune-pkg-dashboard.
  • Based on the findings from the above, several issues were opened on the Dune issue tracker. All the known issues are now tracked in the Package Management MVP milestone on Dune's issue tracker.
  • We also focused on improving features that were previously implemented. Noteworthy changes include the addition of workspace package pins and enhancements for correct path handling in packages – ocaml/dune#9940
  • Work included updates and refactorings to improve source fetching, particularly the removal of a rudimentary Git config parser in favor of using git config directly (ocaml/dune#9905), and enhancements to how Dune handles Git repositories, such as the checking out of Git repos via rev_store (ocaml/dune#10060).
  • Contributions also focused on refining and testing Dune's package handling, including a fix to ensure that opam's untar code is not used (ocaml/dune#10085), and improvements to Dune's handling of recursive submodules in Git repos (ocaml/dune#10130).

[opam] Native Support for Windows in opam 2.2 (W5)

Contributed by: @rjbou (OCamlPro), @kit-ty-kate (Tarides), @dra27 (Tarides), @AltGr (OCamlPro)

Why: Enhance OCaml's viability on Windows by integrating native opam and opam-repository support, fostering a larger community, and more Windows-friendly packages.

What: Releasing opam 2.2 with native Windows support, making the official opam-repository usable on Windows platforms.


  • Addressed the issue where the Windows loader would display blocking dialogue boxes upon failing to find DLLs, adhering to best practices by suppressing these dialogs, and opting for exit codes instead. This enhancement eliminates disruptive interruptions, ensuring a more seamless operation for automated tasks and CI environments. – #5828
  • Fixed shell detection issues when opam is invoked via Cygwin's /usr/bin/env, enhancing compatibility and user experience for those utilising Cygwin alongside cmd or PowerShell. – #5797
  • Recommend Developer Mode on Windows. To optimise storage and align with best practices, Developer Mode is recommended for enabling symlink support. – #5831
  • Resolved issues related to environment variable handling, specifically fixing bugs where updates or additions to environment variables would incorrectly remove or alter them. – #5837
  • Addressed early loading of git location information, particularly benefiting Windows users by ensuring correct retrieval and application of git-related configurations. – #5842
  • Disabled ACL in Cygwin. By setting noacl in /etc/fstab for /cygdrive mount, this change avoids permission mismatch errors, enhancing reliability and usability for Cygwin users. – #5796
  • Introduced the ability to define the package manager path at initialisation, improving customisation and integration capabilities for Windows users. – #5847
  • Added winsymlinks:native to the Cygwin environment variable, improving compatibility within the Cygwin ecosystem. – #5793
  • Fixed script generation issues related to path quoting, ensuring smoother initialisation and setup processes, especially in mixed-environment scenarios like Cygwin. – #5841
  • Corrected the precedence and handling of git-location configurations during initialisation, streamlining Git integration and providing clearer control over Git settings. – #5848
  • Extended the use of eval-variables to internal Cygwin installations and adjusted the setup to better accommodate Windows-specific requirements, enhancing flexibility and system compiler integration. – #5829

[​odoc​] Unify OCaml.org and Local Package Documentation (W25)

Contributed by: @jonludlam (Tarides), @julow (Tarides), @panglesd (Tarides), Luke Maurer (Jane Street)

Why: Improving local documentation generation workflow will help package authors write better documentation for their packages, and consolidating the different odoc documentation generators will help make continuous improvements to odoc available to a larger audience.

What: We will write conventions that drivers must follow to ensure that their output will be functional. Once established, we will update the Dune rules to follow these rules, access new odoc features (e.g., source rendering), and provide similar functionalities to docs.ocaml.org (a navigational sidebar, for instance). This will effectively make Dune usable to generate OCaml.org package documentation.


  • Work continued on the design for the new odoc drivers conventions shared by Dune and OCaml.org, and we plan to publish the RFC in March.
  • We also started comparing and prototyping various approaches to add sidebar support to odoc. Several prototypes have been developed and discussed with the team, and we will resume work on the sidebar implementation once the driver conventions have been adopted.

[​odoc​] Add Search Capabilities to odoc (W25)

Contributed by: @panglesd (Tarides), @EmileTrotignon (Tarides), @julow (Tarides), @jonludlam (Tarides)

Why: Improve usability and navigability in OCaml packages documentation, both locally and on OCaml.org, by offering advanced search options like type-based queries.

What: Implementing a search engine interface in odoc, complete with a UI and a search index. Additionally, we're developing a default client-side search engine based on Sherlodoc.


  • The implementation and refinement of sherlodoc's integration with odoc were our major focuses, this included making sherlodoc pass opam CI on different architectures and adjusting the dune rules for better usability – ocaml/dune#9956
  • After the big sherlodoc PR was merged and sherlodoc released last month, work continued on refining the dune rules for sherlodoc and on adjusting the search bar's scope based on discussions with the team.
  • We implemented keyboard navigation in the search bar to improve its usability – ocaml/odoc#1088

[​odoc​] Improving odoc Performance (W25)

Contributed by: @jonludlam (Tarides), @julow (Tarides), @gpetiot (Tarides)

Why: Address performance issues in odoc, particularly for large-scale documentation, to enhance efficiency and user experience and unlock local documentation generation in large code bases.

What: Profiling odoc to identify the main performance bottlenecks and optimising odoc with the findings.


  • Performance improvements were achieved by addressing issues with source location lookups for non-existent identifiers, significantly improving link time for large codebases.
  • Several PRs from the module-type-of work were opened, including fixes and tests aimed at enhancing odoc's handling of transitive library dependencies, shape lookup, and module-type-of expansions – ocaml/odoc#1078, ocaml/odoc#1081
  • Improve the efficiency of finding odoc files in accessible paths, cutting the time to generate documentation by two in some of our tests – ocaml/odoc#1075

[Merlin] Support for Project-Wide References in Merlin (W19)

Contributed by: @voodoos (Tarides)

Why: Enhance code navigation and refactoring for developers by providing project-wide reference editor features, aligning OCaml with the editor experience found in other languages.

What: Introducing ocamlmerlin server occurrences and LSP textDocument/references support, extending compiler's Shapes for global occurrences and integrating these features in Dune, Merlin, and OCaml LSP.


  • Continued investigations and improvements on Dune rules to address configuration issues
  • After adding support for OCaml 5.2 to merlin-lib, we've rebased the project-wide occurrences work over it.
  • We also started work with the Jane Stree team to test project wide references at scale in their monorepo. Following our initial integration, we focused on refining Merlin's indexing and occurrence query capabilities, including addressing bottlenecks and regressions in shape reductions – ocaml/ocaml#13001

[Merlin] Improving Merlin's Performance (W19)

Contributed by: @pitag (Tarides), @Engil (Tarides)

Why: Some Merlin queries have been shown to scale poorly in large codebases, making the editor experience subpar. Users report that they sometimes must wait a few seconds to get the answer. This is obviously a major issue that hurts developer experience, so we're working on improving Merlin performance when it falls short.

What: Developing benchmarking tools and optimising Merlin's performance through targeted improvements based on profiling and analysis of benchmark results.


  • In merlin-lib, we've continued the work on a prototype to process the buffer in parallel with the query computation. Parallelism refers to OCaml 5 parallelism (domains).

Your Feedback Needed on OCaml Home Page Wireframe!

Claire Vandenberghe announced

I'm reaching out to ask for a few minutes of your time to review the wireframe designs for the OCaml Home, Industrial, and Academic pages.

After conducting user interviews with OCaml enthusiasts, we've gathered valuable insights on what information newcomers find most helpful when visiting the OCaml home.

As a result, we've been working on restructuring these three major pages to better cater to user needs.

(Please note that these wireframes primarily focus on navigation, layout, and content, rather than the User Interface (UI).)

Your feedback is crucial at this stage, so please feel free to leave comments directly on Figma, via email, or let's schedule a quick call to discuss. Thank you for taking part in this review.

Figma Link: https://www.figma.com/file/eLNSdvayxqvvfBsRsdbJXN/OCaml-Home-Page?type=design&node-id=5%3A2500&mode=design&t=hHclskuVpoOzKP2u-1

OCaml Workshop 2024 at ICFP – announcement and call for proposals

Sonja Heinze announced

This year, ICFP (the International Conference on Functional Programming) is going to take place in beautiful Milan.


Such as every year since 2012, on the last day of that conference, i.e. on September 7th (Saturday), we'll hold a workshop on OCaml. The workshop is intended to cover all different kinds of aspects of the OCaml programming language as well as the OCaml ecosystem and its community, such as scientific and/or research-oriented, engineering and/or user-oriented, as well as social and/or community-oriented.

Call for talk proposals

The call for talk proposals for the workshop is open.

  • Dates

    Here are the important dates:

    • Talk proposal submission deadline: May 30th (Thursday)
    • Author notification: July 4th (Thursday)
    • Workshop: September 7th (Saturday)
  • Submissions

    Submissions are typically around 2 pages long (flexible), describing the motivations of the work and what the presentation would be about.

    We encourage everyone who might be interested in giving a talk to submit a proposal! We truly mean everyone, and also have strongly anyone in mind who belongs to a group that's traditionally underrepresented at OCaml workshops, e.g. due to your gender(s) or non-gender, where you're from or based or whatever other kinds of characteristics you might have. You should all be able to find all information you'll need to submit a proposal on the official call for talk proposals. However, if you have any question, don't hesitate to ask us.

  • Quota on accepted talks per affiliation

    Even though none of us is a fan of quotas, last year's workshop experimented with a quota of a maximum of four talks given by speakers with the same company/university/institute affiliation. In order to guarantee a coverage of a diverse range of topics and perspectives, we'll experiment with the same affiliation quota again.

    Do not hesitate to submit your talk proposal in any case: quotas, if needed, will be taken into account by the PC after reviewing all submissions, so there's no reason to self-select upfront.

About the workshop itself

So far, we've only talked about talk proposals and formalities. The really exciting part will be the workshop itself! It's going to be a whole-day workshop and, similarly to previous years, it's likely going to have four sessions of about four talks each. It's a rather informal and interactive environment, where people engage in all kinds of conversations about OCaml during the breaks and after the workshop.

  • Hybrid attendance and cost for speakers

    We're aiming to make the workshop hybrid with the same streaming modalities as last year, meaning that talks as well as participation can be either in-person or remote, and remote attendance will be free. To promote a good atmosphere, communication and engagement, we prefer to have most talks in-person, but remote talks will be most welcome as well.

    We know that giving the talk in-person comes with an economic cost. We're very happy to announce that thanks to the OCaml Software Foundation, registration fees will be covered for speakers in case they can't get them funded by other means (e.g. their employer).

    We will do our best to provide the best workshop experience possible for remote participants, within the constraints of the hybrid format. While attending in-person does come with advantages, it also comes with an environmental cost, and we strongly support transitioning to a less plane-intensive organization for conferences and community events :deciduous_tree: .

  • Related events

    The day before the OCaml workshop, i.e. Sep 6th (Friday), is the day of the ML workshop, with focus on more theoretical aspects of OCaml and the whole family of ML languages in general. The ML workshop has already been announced on the OCaml discuss and tends to be very interesting for OCaml lovers as well.

    We're looking forward to the the talk submissions and to the workshop! Let us know if you have any questions. @Armael and @pitag

down.0.2.0 and omod.0.4.0

Daniel Bünzli announced

It's my pleasure to announce new releases for down and omod which provide a nice ocaml toplevel user experience upgrade. Simply add to your .ocamlinit:

#use "down.top"
#use "omod.top" 

And enjoy all the benefits you can learn about in the down manual and in the omod tutorial.

These are mainly maintenance releases but if you ever though that down was a bit slow when pasting code, it now (well for almost two years…) implements bracketed pastes. Thanks to @emillon for the reference.

stdlib-random 1.2

octachron announced

The library stdlib-random is a small compatibility library that provides compiler-independent implementations of the PRNGs used in the history of the standard library Random:

  • stdlib-random.v3: implement the PRNG used in OCaml 3.07 to 3.11
  • stdlib-random.v4: implement the PRNG used in OCaml 3.12 to 4.14
  • stdlib-random.v5: implement the PRNG currently used in OCaml 5
  • stdlib-random.v5o: implement the PRNG currently used in OCaml 5 in pure OCaml

This library is targeted toward programs that need a deterministic and stable behaviour of the Random module across OCaml versions.

The newly released version 1.2.0 updates all implementations to provide the new int_in_range function (and its int32_in_range, nativeint_in_range, int64_in_range variants) that will be available in OCaml 5.2.0.

Note however that the implementations on the pre-OCaml 5 PRNGs are not optimal, since I prioritised the maintenance cost over performance, but that could be changed if required.

Other OCaml News


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