Cross-Platform Dependencies

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.

Using crossProject (recommended)

The sbt-crossproject plugin provides a crossProject DSL that manages shared and platform-specific source directories automatically. This is the recommended approach for real cross-compilation with shared source code.

// project/plugins.sbt
addSbtPlugin("io.github.matejcerny" % "sbt-config" % "0.6.0")
addSbtPlugin("org.scala-native" % "sbt-scala-native" % "0.5.10")
addSbtPlugin("org.portable-scala" % "sbt-scala-native-crossproject" % "1.3.2")

// build.sbt
lazy val root = crossProject(JVMPlatform, NativePlatform)
  .crossType(CrossType.Full)

By default, the plugin reads build.conf from the build root, so every platform sub-project picks it up automatically. Override sbtConfigFile only if your build.conf lives elsewhere.

If build.conf defines name, that value is used as the published artifact's moduleName for every platform component, regardless of the crossProject val name. The auto-generated root project that only aggregates those components is skipped during publishing, so it does not produce an empty aggregate artifact.

This gives you the standard crossProject directory layout:

shared/src/main/scala/   # shared sources compiled on all platforms
jvm/src/main/scala/      # JVM-only sources
native/src/main/scala/   # Native-only sources

For Scala.js, use sbt-scalajs-crossproject instead:

addSbtPlugin("org.scala-js" % "sbt-scalajs" % "1.20.2")
addSbtPlugin("org.portable-scala" % "sbt-scalajs-crossproject" % "1.3.2")

Manual separate projects (alternative)

If you don't need shared source code and only want platform-aware dependency filtering, you can define separate projects manually:

// project/plugins.sbt
addSbtPlugin("io.github.matejcerny" % "sbt-config" % "0.6.0")
addSbtPlugin("org.scala-js" % "sbt-scalajs" % "1.20.2")
addSbtPlugin("org.scala-native" % "sbt-scala-native" % "0.5.10")

// build.sbt
lazy val jvm = project.in(file("jvm"))

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

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

All 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

The real distinction between scala and js/native here is scope, not operator: scala (and java) deps are shared — included in every platform — while js/native deps are platform-specific. All Scala deps adapt their cross-version automatically via the active platform plugin, so a shared scala dep resolves as %% on the JVM and %%% in a Scala.js / Scala Native project.

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:

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"]
}