build.scala

import sbt._
import Keys._

object build extends Build {
  
  // usage example
  lazy val example = Project(
    "example",
    file("."),
    settings = Defaults.defaultSettings ++ Nucleus.settings ++ Seq(
      scalaVersion := "2.9.1",
      name := "example",
      libraryDependencies ++= Seq(
        "org.datanucleus" % "datanucleus-core" % "3.0.1",
        "org.datanucleus" % "datanucleus-api-jdo" % "3.0.1",
        "javax.jdo" % "jdo-api" % "3.0"
      )
    )
  )
}

// should be fairly simple to turn this into a plugin
// https://github.com/harrah/xsbt/wiki/Plugins
object Nucleus {
  
  // defines our own ivy config that wont get packaged as part of your app
  // notice that it extends the Compile scope, so we inherit that classpath
  val Config = config("nucleus") extend Compile

  // our task
  val enhance = TaskKey[Unit]("enhance")

  // impementation
  val settings:Seq[Project.Setting[_]] = Seq(
    // let ivy know about our "nucleus" config
    ivyConfigurations += Config,
    // add the enhancer dependency to our nucleus ivy config
    libraryDependencies += "org.datanucleus" % "datanucleus-enhancer" % "3.0.1" % Config.name,
    // fetch the classpath for our nucleus config
    // as we inherit Compile this will be the fullClasspath for Compile + "datanucleus-enhancer" jar 
    fullClasspath in Config <<= (classpathTypes in enhance, update).map{(ct, report) =>
      Classpaths.managedJars(Config, ct, report)
    },
    // add more parameters as your see fit
    enhance in Config <<= (fullClasspath in Config, runner, streams).map{(cp, run, s) =>
      // the classpath is attributed, we only want the files
      val classpath = cp.files
      // the options passed to the Enhancer... 
      val options = Seq("-v")
      
      // run returns an option of errormessage
      val result = run.run("org.datanucleus.enhancer.DataNucleusEnhancer", classpath, options, s.log)
      // if there is an errormessage, throw an exception
      result.foreach(sys.error)
    }
  )
}