Advanced configurations example 

This is an example .sbt build definition that demonstrates using configurations to group dependencies.

The utils module provides utilities for other modules. It uses configurations to group dependencies so that a dependent project doesn’t have to pull in all dependencies if it only uses a subset of functionality. This can be an alternative to having multiple utilities modules (and consequently, multiple utilities jars).

In this example, consider a utils project that provides utilities related to both Scalate and Saxon. It therefore needs both Scalate and Saxon on the compilation classpath and a project that uses all of the functionality of ‘utils’ will need these dependencies as well. However, project a only needs the utilities related to Scalate, so it doesn’t need Saxon. By depending only on the scalate configuration of utils, it only gets the Scalate-related dependencies.

// Custom configurations
lazy val Common = config("common").describedAs("Dependencies required in all configurations.")
lazy val Scalate = config("scalate").extend(Common).describedAs("Dependencies for using Scalate utilities.")
lazy val Saxon = config("saxon").extend(Common).describedAs("Dependencies for using Saxon utilities.")

// Define a customized compile configuration that includes
// dependencies defined in our other custom configurations
lazy val CustomCompile = config("compile").extend(Saxon, Common, Scalate)

// factor out common settings
ThisBuild / organization := "com.example"
ThisBuild / scalaVersion := "2.12.18"
ThisBuild / version      := "0.1.0-SNAPSHOT"

// An example project that only uses the Scalate utilities.
lazy val a = (project in file("a"))
  .dependsOn(utils % "compile->scalate")

// An example project that uses the Scalate and Saxon utilities.
// For the configurations defined here, this is equivalent to doing dependsOn(utils),
//  but if there were more configurations, it would select only the Scalate and Saxon
//  dependencies.
lazy val b = (project in file("b"))
  .dependsOn(utils % "compile->scalate,saxon")

// Defines the utilities project
lazy val utils = (project in file("utils"))
  .settings(
    inConfig(Common)(Defaults.configSettings),  // Add the src/common/scala/ compilation configuration.
    addArtifact(Common / packageBin / artifact, Common / packageBin), // Publish the common artifact

    // We want our Common sources to have access to all of the dependencies on the classpaths
    //   for compile and test, but when depended on, it should only require dependencies in 'common'
    Common / classpathConfiguration := CustomCompile,

    // Modify the default Ivy configurations.
    // 'overrideConfigs' ensures that Compile is replaced by CustomCompile
    ivyConfigurations := overrideConfigs(Scalate, Saxon, Common, CustomCompile)(ivyConfigurations.value),

    // Put all dependencies without an explicit configuration into Common (optional)
    defaultConfiguration := Some(Common),

    // Declare dependencies in the appropriate configurations
    libraryDependencies ++= Seq(
       "org.fusesource.scalate" % "scalate-core" % "1.5.0" % Scalate,
       "org.squeryl" %% "squeryl" % "0.9.5-6" % Scalate,
       "net.sf.saxon" % "saxon" % "8.7" % Saxon
    )
  )