An sbt plugin that compiles SCSS to CSS at build time using dart-sass-embedded (no Node required), with a custom importer that resolves @import / @use statements against WebJar JARs on the build classpath.

Supports sbt 1.x and sbt 2.x.

In project/plugins.sbt:

addSbtPlugin("com.jamesward" % "sbt-sass" % "<version>")

The plugin auto-enables on every JVM project — no enablePlugins(...) needed.

1. Put SCSS sources in src/main/scss/:

   src/main/scss/app.scss
   

2. Add WebJar dependencies scoped to "sass":

   libraryDependencies += "org.webjars.npm" % "bootstrap" % "5.3.8" % "sass"

   Or, if you also use sbt-webjars:

   libraryDependencies += "org.webjars.npm" % "bootstrap" % "5.3.8" % Set(WebJar, Sass, Test)

3. Import from WebJars using the artifact name as the first path segment:

   // src/main/scss/app.scss
   @import "bootstrap/scss/bootstrap";

4. Run compile — CSS appears at runtime on the classpath under public/:

   target/.../resource_managed/main/public/app.css
   target/.../resource_managed/main/public/app.css.map
   

   Source maps are emitted with SCSS sources inlined for DevTools.

sassCompile is wired into Compile / resourceGenerators, so compile, run, package, etc. all trigger SCSS compilation automatically.

The plugin ships WebJarsScssImporter, which resolves imports using webjars-locator-core. For each import it tries the standard SCSS file-resolution order:

1. _<name>.scss
2. <name>.scss
3. <name>/_index.scss
4. <name>/index.scss

This means @import "bootstrap/scss/functions" resolves to _functions.scss inside the bootstrap WebJar JAR — just like a local Sass install would.

./sbt +compile        # cross-build for sbt 1.x and 2.x
./sbt scripted        # run integration tests
./sbt +publishLocal   # install locally for both sbt versions

MIT