Apr 8, 2019.

We are pleased to announce the release of Scala.js 0.6.27!

The highlight of this release is the support for Scala 2.13.0-RC1. It also fixes a few issues, and introduces a way to limit the number of concurrent linking operations in the sbt plugin.

Read on for more details.

Getting started

If you are new to Scala.js, head over to the tutorial.

Release notes

If you use .scala build files in project/ and are upgrading from Scala.js 0.6.22 or earlier, do read the release notes of 0.6.23, which contain a source breaking change in that situation.

If upgrading from Scala.js 0.6.14 or earlier, make sure to read the release notes of 0.6.15, which contain important migration information.

As a minor release, 0.6.27 is backward binary compatible with previous releases in the 0.6.x series. Libraries compiled with earlier versions can be used with 0.6.27 without change. 0.6.27 is also forward binary compatible with 0.6.{17-26}, but not with earlier releases: libraries compiled with 0.6.27 cannot be used by projects using 0.6.{0-16}.

Please report any issues on GitHub.

Limit how many Scala.js linker tasks can concurrently run in sbt

Linker tasks (fastOptJS and fullOptJS), which are transitively called by run and test tasks, use a lot of memory. In some environments, and in particular on CI machines, this can lead to memory exhaustion and fail builds. You can now use the following sbt setting to limit how many such tasks can concurrently run:

concurrentRestrictions in Global += Tags.limit(ScalaJSTags.Link, 2)

You may want to systematically enable that setting in your CI jobs.

Bug fixes

Among others, the following bugs have been fixed in 0.6.27:

• #3575 Wrong optimizations on floating point comparisons, e.g. !(x <= 0) ⟶ x > 0
• #3538 Incorrect codegen for @JSExport on method with variable arguments in trait
• #3528 NodeJSEnv does not propagate error output from Node.js

You can find the full list on GitHub.