sbt-uni-crossproject Plugin

sbt-uni-crossproject lets one source tree cross-build for JVM, Scala.js, and Scala Native. It is a small, uni-owned re-implementation of portable-scala/sbt-crossproject, which has not been ported to sbt 2.x.

It provides just the surface uni uses: crossProject(...) with the CrossType.Pure layout — shared sources in <base>/src, platform-specific code in <base>/.jvm, .js, and .native.

sbt 2.x only

The plugin targets sbt 2.x (its metabuild runs on Scala 3). It is not published for sbt 1.x — if you are on sbt 1.x, use the original sbt-crossproject instead.

One plugin, all three platforms

Unlike upstream's three separate artifacts (sbt-crossproject + sbt-scalajs-crossproject + sbt-scala-native-crossproject), this is a single plugin that depends on both sbt-scalajs and sbt-scala-native and defines all three platforms.

Installation

In project/plugins.sbt, add the Scala.js and Scala Native plugins (for their scalaJSLinkerConfig / nativeConfig settings) and this one:

addSbtPlugin("org.scala-js"     % "sbt-scalajs"          % "1.22.0")
addSbtPlugin("org.scala-native" % "sbt-scala-native"     % "0.5.12")
addSbtPlugin("org.wvlet.uni"    % "sbt-uni-crossproject" % "2026.1.20")

The plugin is triggered automatically, so crossProject, the platforms, and CrossType are available in build.sbt without an explicit enablePlugins.

Usage

lazy val core = crossProject(JVMPlatform, JSPlatform, NativePlatform)
  .crossType(CrossType.Pure)
  .in(file("core"))
  .settings(/* shared settings */)
  .jvmSettings(/* JVM-only */)
  .jsSettings(/* Scala.js-only */)
  .nativeSettings(/* Scala Native-only */)

lazy val app = crossProject(JVMPlatform, JSPlatform, NativePlatform)
  .crossType(CrossType.Pure)
  .in(file("app"))
  .dependsOn(core, core % "test")

crossProject must be assigned directly to a val — it derives the project id from the val name (just like sbt's own project). So val core = … defines the sub-projects coreJVM, coreJS, and coreNative, which you reach as core.jvm, core.js, and core.native (e.g. when aggregating or depending on a single platform):

lazy val root = project
  .in(file("."))
  .aggregate(core.jvm, core.js, core.native, app.jvm, app.js, app.native)

sbt> coreJVM/test

sbt 2.x dependencies

On sbt 2.x, %% already encodes the platform suffix (_sjs1 for Scala.js, _native0.5 for Native), so use %% (not the old %%%) for your cross-platform library dependencies inside .settings(...).

Directory layout (CrossType.Pure)

core
├── .js      // core/.js/src/main/scala     — Scala.js-only sources
├── .jvm     // core/.jvm/src/main/scala     — JVM-only sources
├── .native  // core/.native/src/main/scala  — Scala Native-only sources
└── src      // core/src/main/scala          — shared across all platforms
             // core/src/main/scala-3, scala-2.13, ... — shared, version-specific

Shared sources live under <base>/src. Scala-version-specific shared sources (src/main/scala-3, src/main/scala-2.13, …) are picked up too when crossPaths is enabled (the default). The same structure applies under src/test for tests.

Supported API

The cross-project value supports the methods uni's own build relies on:

Method	Description
.crossType(CrossType.Pure | CrossType.Full)	Choose the directory layout (default Pure)
.in(file("..."))	Set the cross-project base directory
.settings(...)	Settings applied to every platform project
.jvmSettings / .jsSettings / .nativeSettings	Settings applied to one platform only
.configure(...) / .jvmConfigure / .jsConfigure / .nativeConfigure	Apply Project => Project transforms
.enablePlugins(...) / .disablePlugins(...)	Enable/disable sbt plugins on every platform project
.dependsOn(other, other % "test")	Depend on another cross-project, optionally scoped to a config
.aggregate(other)	Aggregate another cross-project
.jvm / .js / .native	The underlying single-platform Project for that platform

Scope

Only the CrossType.Pure (and CrossType.Full) layouts are supported. Upstream features uni does not use — partially-shared sources, the Dummy layout, and withoutSuffixFor — are intentionally omitted.