Tweag

Introduction to the new LaunchDarkly Svelte SDK Introducting the new LaunchDarkly Svelte SDK

In our latest blog post, Robinson Marquez introduces the new LaunchDarkly Svelte SDK that he contributed. Letting you toggle features in real-time and run A/B tests in Svelte applications. Complete with a tutorial www.tweag.io/blog/2025-07...

#Svelte #FeatureFlags #LaunchDarkly #WebDevelopment

Our Scalable Build Group has just published issue 30 of their build //newsletter. Subscribe for updates on the latest developments in the build system space: www.build.news

#opensource #engineering

Polymorphic Parameters by voodoos · Pull Request #13806 · ocaml/ocaml This upstreaming PR adds the possibility to have function parameters with polymorphic types in the language. This work was originally done by @lpw25 in Jane Street's fork of the compiler with e...

Yet another small OCaml/OxCaml diff has been squished! Polymorphic parameters has just gotten merged upstream:

github.com/ocaml/ocaml/...

There's more to go (include functor, for example: github.com/ocaml/RFCs/p...), but it's nice to see more progress in this space.

How GHC is evolving to support WebAssembly and why it mattersCheng Shao presents the architecture, challenges, and current status of the GHC backend for WebA... Compiling Haskell to WebAssembly – Cheng Shao (GHC/Wasm Backend Developer)

The videos for Zurihac 2025 are online. Our own Cheng Shao, main author of GHC's Wasm backend, taught everything you need to know to build your own Haskell Wasm app in five lessons. www.youtube.com/watch?v=9zv0...

What about you? What was your favourite presentation?

We're curating an exhibit on #code as culture for ‪@unesco.org‬ . Got a snippet & a story? Submit by Sept 8. https://www.softwareheritage.org/2025/07/07/code-exhibit-unesco-cfp/

Publish all your crates everywhere all at once A new multi-crate packaging feature for Cargo

Publishing crates from a #Rust workspace just got easier, thanks to the newly stabilized workspace-publishing feature that we contributed last year.
Here’s how it works — and how you can use it now (blog post by Joe Neeman): www.tweag.io/blog/2025-07...

Infrastructure Independence | Haskell.org, Inc (Powered by Donorbox) Historically, the Haskell community has relied on a mix of cloud providers and self-hosted servers for our core infrastructure (Hackage, Stackage, GHC, CI, etc.). More recently the Haskell Infrastruct...

Better infrastructure, fewer surprises. We’re raising $6K for a dedicated ARM server to support #Haskell’s infrastructure (CI, backups, etc). Let’s build infra you can rely on! Every contribution helps!

Donate: donorbox.org/infrastructu...
Read more: discourse.haskell.org/t/infrastruc...

PSA! Please share around! Due to a limited number of submissions, we're extending the OCaml Workshop deadline by a week to July 10th AoE!

Functional programmers! Heed my call! We need your submissions!!

🚨 Call for Volunteers: SPLASH/ICFP 2025 🚨

Join the team that makes it all happen!
Meet the PL community, attend for free, and help run an amazing conference.

Apply now 👉 tinyurl.com/splashifcp25...

More info 👉 conf.researchr.org/track/icfp-s...

Bazel workshop made public The materials from a Bazel workshop we developed for a client are now publicly available

We are making public a #Bazel workshop we created for a client last year! Mark Karpov and Johan Herland wrote a short blog post with more information www.tweag.io/blog/2025-07...

GitHub - tweag/gazelle_cabal: A gazelle extension to produce Haskell rules from cabal files A gazelle extension to produce Haskell rules from cabal files - tweag/gazelle_cabal

If you really want to build something for Hackage with Bazel, we built a Gazelle generator github.com/tweag/gazell... it's more work to keep things in sync, you'll probably have to spend more time working in your build system, so only worth it if the compilation times are really very large.

If you can naturally split your project in decently large chunks (say that take more than 10s to compile) and put them each in a separate Cabal library, Nix is going to do a good job at caching your CI.

If it's not, then you have much more flexibility. We like to pair Bazel for build and Nix for the non-Haskell dependencies. Or if you have a little more dependency budget Buck2 for build and Nix for deps (including Haskell's, Buck2 doesn't have much support for dependencies yet).

Having asked the team, the answer is a solid: it depends.

If you're building a library that you want to publish on Hackage (we're assuming you're writing Haskell) then you need to maintain Cabal files, and Bazel isn't ready for that. Probably use Nix for the submodules, Cabal for the rest.

the ICFP 2025 program is coming together! Check out our list of accepted papers: icfp25.sigplan.org/track/icfp-2...

and we'll have three keynotes this year!
icfp25.sigplan.org/track/icfp-2...

⬇️⬇️⬇️

Demain vendredi, lors de @lu.voxxeddays.com venez me voir en salle Amiga OS à 16h30 🎤🥳

Je vais parler builds incrémentaux 💪 caches locaux & remote, pour vos monorepos ou codebases qui mélangent plusieurs languages. Avec des outils open-source comme #bazel #pants ou #buck2

Blog post: Indexing Hackage: Glean vs. hiedb
simonmar.github.io/posts/2025-0...

FUNARCH 2025 - ICFP/SPLASH 2025 The Third ACM SIGPLAN Workshop on Functional Software Architecture - FP in the Large “Functional Software Architecture” refers to methods of construction and structure of large and long-lived softwar...

We've extended the deadline for FUNRARCH 2025 to June 23rd.
Know something about what makes functional programming work in the large? Write it up!
conf.researchr.org/home/icfp-sp...

And here's a blog post, announcing the release!

blog.janestreet.com/introducing-...

I'm pleased to announce OxCaml!

OxCaml is Jane Street's branch of OCaml. We've given it a new name and a snazzy logo, and done a bunch of work to make it easy for people to try.

Pick your track! As always, we're giving you lots of incredible talks to choose from. But don't worry if some that you're interested in overlap - after the conference you get access to all recorded presentations.

#lambdadays

@devlille.fr démarre demain ! Mon exposé sur direnv.net a lieu vendredi à 15h45 en salle Louis Pasteur.

Je vais expliquer comment #direnv offre une opportunité aux leaders d'introduire reproducibilité et bonnes pratiques, avec zéro friction ! 💪 #devex

drive.google.com/file/d/1xGFz...

In this episode we learn about @andygordon.bsky.social'’s work including the origins of (>>=), introducing lambdas in Excel, and delve into his current work at Cogna using AI to allow non-programmers to write apps using natural language.

haskell.foundation/podcast/65/

FUNARCH 2025 - ICFP/SPLASH 2025 The Third ACM SIGPLAN Workshop on Functional Software Architecture - FP in the Large “Functional Software Architecture” refers to methods of construction and structure of large and long-lived softwar...

Only a single week to go until the deadline on Monday, June 16th: Send us your paper on FP in the large - to the SIGPLAN Workshop on Functional Software Architecture! Happy Writing! conf.researchr.org/home/icfp-sp...

Prompted by Hécate (last year 😅) I finally wrote up a blog post on why you should use the `Generically` newtype instead of DefaultSignatures in @haskell.org

jvanbruegge.github.io/blog/2025/pl...

We currently don't have a plan for a separate account, I'm afraid. Ultimately, if such an account is to be created it doesn't have to come from Tweag/Modus Create, though. If the community is large enough, there can be a community managed account.

Release v0.20.0 · tweag/FawltyDeps As we're nearing the release of v1.0, here is an update with various quality-of-life improvements. Suggesting package names for undeclared dependencies When FawltyDeps finds a 3rd-party import that...

Read the Full release notes: github.com/tweag/Fawlty...

Release v0.20.0 · tweag/FawltyDeps As we're nearing the release of v1.0, here is an update with various quality-of-life improvements. Suggesting package names for undeclared dependencies When FawltyDeps finds a 3rd-party import that...

#FawltyDeps v0.20.0 released, with a few quality-of-life improvements.
- FawltyDeps is more clever when the import name isn't the same as the package name.
- New --base-dir option to control where FawltyDeps looks for 1st-party imports tweag.github.io/FawltyDeps/F...

The VSCode extension has been bumped to 0.5 and published (it should be live by now), and as always, pre-built binaries might take a bit more time, but be there later today.

#Nickel 1.12 is out! It comes with the long-awaited field punning feature, aka "Nix inherit", or include expressions in Nickel. The CLI now accepts non-Nickel input (e.g. validation of a JSON config using Nickel contracts).

Read the full release notes: github.com/tweag/nickel...