Chapter 22. The Scala Plugin

To use the Scala plugin, include in your build script:

apply plugin: 'scala'

The Scala plugin adds the following tasks to the project.

The Scala plugin adds the following dependencies to tasks added by the Java plugin.

Figure 22.1. Scala plugin - tasks

The Scala plugin assumes the project layout shown below. All the Scala source directories can contain Scala and Java code. The Java source directories may only contain Java source code. None of these directories need exist or have anything in them. The Scala plugin will compile whatever it finds, and handles anything which is missing.

sourceSets {
    main {
        scala {
            srcDir 'src/scala'
        }
    }
}

The Scala plugin adds a scalaTools configuration, which it uses to locate the Scala tools, such as scalac, to use. You must specify the version of Scala to use. Below is an example.

repositories {
    mavenCentral()
}

dependencies {
    // Libraries needed to run the scala tools
    scalaTools 'org.scala-lang:scala-compiler:2.8.1'
    scalaTools 'org.scala-lang:scala-library:2.8.1'

    // Libraries needed for scala api
    compile 'org.scala-lang:scala-library:2.8.1'
}

The Scala plugin does not add any convention properties to the project.

The Scala plugin adds the following convention properties to each source set in the project. You can use these properties in your build script as though they were properties of the source set object (see Section 18.2, “Using the convention object”).

These convention properties are provided by a convention object of type ScalaSourceSet.

The Scala plugin also modifies some source set properties:

The Scala plugin includes support for fsc, the Fast Scala Compiler. fsc runs in a separate daemon process and can speed up compilation significantly.

compileScala {
    scalaCompileOptions.useCompileDaemon = true

    // optionally specify host and port of the daemon:
    scalaCompileOptions.daemonServer = "localhost:4243"
}

Note that fsc expects to be restarted whenever the contents of its compile class path change. (It does detect changes to the compile class path itself.) This makes it less suitable for multi-project builds.