Cross-Platform Dependencies (Experimental)

Experimental

Cross-platform dependency support (Scala.js, Scala Native) is experimental. It may not work correctly and may change in future versions.

For projects that target Scala.js or Scala Native, the plugin supports additional dependency keys and platform-aware filtering.

Setup

Cross-platform projects still require a build.sbt to enable platform plugins and define sub-projects — build.conf handles only the dependencies and metadata. A minimal setup for a JVM + Scala.js + Scala Native project:

// project/plugins.sbt
addSbtPlugin("io.github.matejcerny" % "sbt-config" % "0.5.0")
addSbtPlugin("org.scala-js" % "sbt-scalajs" % "1.20.2")
addSbtPlugin("org.scala-native" % "sbt-scala-native" % "0.5.10")

// build.sbt
val commonSettings = Seq(
  sbtConfigFile := (ThisBuild / baseDirectory).value / "build.conf"
)

lazy val jvm = project.in(file("jvm"))
  .settings(commonSettings)

lazy val js = project.in(file("js"))
  .enablePlugins(ScalaJSPlugin)
  .settings(commonSettings)

lazy val native = project.in(file("native"))
  .enablePlugins(ScalaNativePlugin)
  .settings(commonSettings)

All three sub-projects share the same build.conf; the plugin automatically detects each project's platform and filters dependencies accordingly.

Language-Split Format

Use js and native keys alongside scala and java:

dependencies {
  scala  = ["org.typelevel:cats-core:2.13.0"]
  java   = ["com.google.code.gson:gson:2.11.0"]
  js     = ["org.scala-js:scalajs-dom:2.8.0"]
  native = ["com.armanbilge:epollcat:0.1.6"]
}

Key Mapping

Key	sbt Operator	Description
scala	%%	Standard Scala cross-versioned library
java	%	Plain Java library (no cross-version)
js	%%%	Scala.js library (requires sbt-scalajs plugin)
native	%%%	Scala Native library (requires sbt-scala-native plugin)

In this format, scala and java dependencies are treated as shared (included in all platforms), while js and native are platform-specific.

Full Matrix Format

For cross-compiled projects (JVM + Scala.js / Scala Native), use explicit platform grouping:

dependencies {
  shared {
    scala = ["org.typelevel:cats-core:2.13.0"]
  }
  jvm {
    scala = ["org.typelevel:cats-effect:3.5.0"]
    java  = ["com.google.code.gson:gson:2.11.0"]
  }
  js     = ["org.scala-js:scalajs-dom:2.8.0"]
  native = ["com.armanbilge:epollcat:0.1.6"]
}

The shared and jvm blocks are objects containing scala and/or java keys. The js and native keys are flat lists (all platform-specific deps use %%%).

Platform-Aware Filtering

Dependencies are automatically filtered based on the active platform. The plugin auto-detects which platform a project targets by inspecting the cross-version set by sbt-scalajs or sbt-scala-native:

Block	JVM project	Scala.js project	Scala Native project
shared	included	included	included
jvm	included	excluded	excluded
js	excluded	included	excluded
native	excluded	excluded	included

Overriding Platform Detection

The detected platform is exposed as the sbtConfigPlatform setting. If auto-detection doesn't work for your setup, you can override it explicitly:

sbtConfigPlatform := Platform.Js     // or Platform.Native, Platform.Jvm

Test Dependencies

Test dependencies also support all cross-platform formats:

testDependencies {
  scala = ["org.scalatest:scalatest:3.2.19"]
  js    = ["org.scala-js:scalajs-test-interface:1.0.0"]
}