This page lists the projects that the Scala Center are working on during the current quarter. We also post regular updates about our projects on the Scala Contributors forum.

To have more information about our completed projects, please see the quarterly activity reports.

Roadmap for 2023 Q2

The following sections present our plan for the current quarter. Every project description is followed by the concrete results we will deliver and their expected outcome on the Scala community.

Language, Compiler, Standard Library

Our mission is to reduce the number of bugs in the compiler implementation, to help the community to contribute to these tools, and to make sure they evolve in a way that takes into account the needs of the community.

Evolve the Standard Library

The standard library has not changed (except for bug fixes or some performance improvements) since Scala 2.13, which was released almost four years ago. The compatibility policy of the standard library forbids the addition of new features (new classes or methods). Furthermore, some bug fixes or performance improvements can not be applied because those compatibility guarantees.

Dropping the forwards binary compatibility requirement would be a first step to allow the introduction of new classes or the addition of new members to the existing classes. Then, we will create a process to validate what should be in the standard library and what should stay outside of it.

Scala Improvement Process

The Scala Improvement Process is a process for submitting changes to the Scala language. It aims to evolve Scala openly and collaboratively. We have restarted the process in 2022, and we now have regular committee meetings.

Generalized Vararg Expansion

Currently, vararg methods can be passed either several arguments, or a single collection of values. We believe it would be useful to also be able to pass a mix of collections and individual argument values:

List(1, 2, 3)         // several individual arguments
List((1 to 3)*)       // a single collection
List((1 to 3)*, 4, 5) // a collection and several individual arguments

We currently have a basic implementation of the feature, we now need to open a PR and a SIP.

Documentation and Education

Our mission is to simplify the structure and content of the website, to create and maintain high-quality online educational content (including online courses), and to help the community to contribute to the website.

Scala Website

We plan to modernize the Scala website, and to integrate better the Scala 2 and Scala 3 documentation.

Following up on the work we did in the previous quarter, we plan to polish further the content of the website.

The next main tasks are:

  • Make the landing page more use-case oriented than language-feature oriented,
  • Include testimonials from adopters of Scala,
  • Polish and complete the integration of both Scala 2 and Scala 3 content (track our progress in docs.scala-lang#2481).

Tutorials Documenting the Toolkit

The Scala Toolkit is a collection of libraries that focus on simplicity over flexibility or power. Our goal is to make it simpler to use Scala for scripting, to perform some very common programming tasks such as reading and writing files, sending HTTP requests, parsing JSON etc. We selected MUnit for testing, OS-Lib for working with files and processes, UPickle for handling JSON and sttp for sending HTTP requests. We packaged and published the Toolkit in the new scala/toolkit repository.

In partnership with VirtusLab and Lightbend, we will contribute to the creation of tutorials demonstrating how to solve typical programming tasks such as ‘How to write a file?’, ‘How to serialize an object to JSON?’, ‘How to send an HTTP request?’. You can track our progress at scalacenter/docs.scala-lang#7.

Language Specification

Currently, there is no proper language specification for Scala 3. A specification would be useful for developers, when they want to quickly check something about a feature they are using. It would also be useful to the Scala Improvement Process, to provide a basis for discussions and proposals.

Some pieces of specification are available in the Scala 3 Reference, but these pieces are mostly about the differences compared to Scala 2. We will complete them, and publish a proper language specification for Scala 3.

Developer Experience

Our mission is to make sure the tools Scala developers use to edit, analyze, navigate through, transform, compile, run, and debug Scala programs are as easy to use as possible, that they work reliably for everyone, and deliver a great developer experience.

Streamline the Scala Installation Procedure

Coursier is the recommended tool to set up and manage a Scala development environment.

However, currently the installation procedure is a bit complicated to follow: there are many branches depending on your underlying operating system and computer architectures.

Instead, macOS and Linux users should be able to run a command like:

curl | sh

That would automatically download the right binaries and invoke cs setup.

For Windows users, we would like to fix the following issues: dotty#12550, coursier#1855, coursier#1858.

You can track our progress here.

Reduce the Number of Ways to Import Scala Projects in IDEs

Currently, when starting new projects in Metals the build server that is used by default is Bloop. Part of this is for historical reasons, but part of it is also due to the speed of Bloop and the integrations that exist for it. Bloop has been incredibly important in the Build Server arena. However, there is also BSP implementation in sbt and in Mill and even when a .bsp/<build-tool>.json entry exists, Metals will still force Bloop on the user unless they manually switch. This can cause confusion and also may add extra steps into choosing a build server that shouldn’t be needed.

This problem also exists in a different way in IntelliJ when you open for example an sbt project that has an existing .bsp/sbt.json file you’ll be prompted to import the project either as a BSP project or an sbt project. Arguably, newcomers have no idea what BSP is, and they shouldn’t have to.

We’d like to minimize the number of ways to import projects and revisit the default choices that Metals makes of using Bloop no matter the build tool. The aim is to make the experience a newcomer has smoother, abstracting away things like Bloop and BSP, while still allowing for a powerful user experience for advanced users. Read the full roadmap and progress reports here.

Bring the Compiler’s Suggestions into the IDEs

Currently, IDEs such as IntelliJ and Metals provide “Quick fix” actions able to fix some types of errors in Scala programs. The way these actions are currently implemented relies on parsing and analyzing the text output of the compiler. This is not efficient because any new “Quick fix” requires additional work in both IntelliJ and Metals.

Instead, we would like the compiler itself to produce structured information that could be automatically processed by the IDEs. Thus, providing a “Quick fix” would only require some little work in the compiler, and the result would be available in both IntelliJ and Metals.

Scala Debugger

The scala-debug-adapter is an implementation of the Debug Adapter Protocol for Scala. It allows users of VSCode to debug their Scala programs, using features such as breakpoints, conditional breakpoints, debug console, log-points and more.

We would like to improve the following points:

  • Implement a faster expression evaluator for simple expressions (read a more detailed description here),
  • Filter out synthetic method from the call-stack (read a more detailed description here),
  • Add support for step-by-step execution of programs that contain inlined method calls (read a more detailed description here).

Create a Stable API for the Scala 3 Presentation Compiler

Currently, Metals works only for a limited subset of Scala 3 versions. Furthermore, we need to publish a new release of Metals after every new release of the compiler to support it.

We would like to create a stable API for the Scala 3 presentation compiler to untie Metals to the compiler release cycle and support a wider range of Scala 3 versions (including experimental versions of Scala 3).

You can track our progress here.

Fix the “Maven Coordinates” of sbt Plugins

The Maven coordinates of sbt plugins do not conform to the Maven specification, as described in sbt#3410. This is causing a number of issues:

  • Maven cannot resolve sbt plugin artifacts.
  • Other resolution tools, like Coursier, must implement some sbt-specific hack to resolve them.
  • Some Maven proxies cannot check the validity of sbt plugins and they reject them.
  • The number of downloads of sbt plugins are unavailable on
  • cannot find the scaladoc of sbt plugins.
  • And more

We implemented a solution that enables a smooth transition to valid Maven pattern of sbt plugins in sbt#7096. This solution will be available in sbt 1.9.x, with bidirectional compatibility: sbt 1.9.x will publish the valid and legacy artifacts of sbt plugins, and will be able to resolve the valid or legacy artifacts of sbt plugins.

The next steps are to adapt sbt 2.x to publish sbt plugins with valid coordinates, and to update Scaladex to correctly index sbt plugins published with the new format.

Twirl Support in Metals

Twirl is a template language and engine for Scala. The Twirl templates contain blocks of Scala code, and they compile to Scala functions.

We will add support for Twirl files in Metals by using the Twirl engine. Corresponding feature request: metals-feature-requests#50.

Community and Contributor Experience

Our mission is to create the best environment for the emergence of a strong Scala ecosystem made of high-quality, reliable, libraries that bring simple solutions to complex problems.


Scastie is an online Scala playground that allows everyone to write, run, and share Scala programs from their web browser.

Currently, the dependencies and compiler options of a Scastie program are modeled as an sbt build definition. This approach has some drawbacks: the configuration of the program is separate from its code, and in order to run a Scastie program locally, users have to download a zip file containing an sbt project definition and then use sbt, and, last, the loading time of sbt creates a significant overhead.

As an alternative, we would like to allow the users to configure their programs via configuration directives embedded in comments.

You can track the progress of this project here.

Another current limitation of Scastie is that programs have to be contained in a single file. This can be an issue when using macros, which require separate compilation, or when working on a large program.

We would like to add support for multiple files to fix those issues. This has impacts on many levels, including the UI design. You can track the progress of this project here.

Scala Contributors Academy

We have been organizing for almost two years now recurring Sprees to onboard new contributors to the Scala 3 compiler. In a blog post in Fall, we explained how we were creating small teams of 2-3 contributors hacking together, remotely, on the Scala 3 compiler. We also shared the YouTube channel of the Scala 3 Compiler Academy, where we regularly post educational videos about how the compiler works.

We would like to expand the scope of the academy to projects outside the compiler, and outside the Scala Center. We will train local Scala user groups to conduct their own iterations of the Sprees in their city, offline.


We will conduct many actions aiming at communicating a positive image of Scala, and making people excited about it.

  • We will regularly share our achievements and engage the community on our projects via our LinkedIn page,
  • We will create an online shop where individual will be able to give donations to the Scala Center in exchange for goodies,
  • We will speak at tech conferences and local meetups to encourage people to contribute to the Scala ecosystem, and to let non-Scala programmers know about Scala,
  • We will publish two new videos in the series Let’s talk about Scala 3 to highlight the strengths of Scala 3.

Maintenance Work

We will also spend a small part of our time reviewing pull requests, triaging issues, and sometimes implementing pull requests for the following projects, to make sure important points are addressed:

  • Scala 3 compiler
  • Scala 2 TASTy reader
  • Scaladex
  • Scastie
  • Coursier
  • sbt

Advisory Board Proposals

For reference, you can see here the list of Advisory Board proposals and their respective status.