Changes from 0.4 to 0.4.3

The changes in this release are mainly minor improvements and fixes in support of the new launcher. There is one important change to managing Scala jars that should be noted before updating. See the Scala Jars and Dependency Management section below and please ask if you have any questions about it.

New Features

  • Dependencies on Scala are checked and filtered. Please read the Scala Jars and Dependency Management section below!
  • ParentProjects now have dependency management tasks (like update) defined.


  • Print version of sbt and Scala on project startup:
  • [info] Building project dispatch 0.1-SNAPSHOT using Dispatch
    [info]    with sbt 0.4.3 and Scala 2.7.3
  • Launcher prompts if versions could not be retrieved:
  • Could not retrieve sbt 0.4.4. Select different version? (y/N) : y
    sbt version [0.4.3]:
  • Print note when scala.version or sbt.version are changed that reboot is required:
  • > set sbt.version 0.4.3
     Build will use sbt 0.4.3 after running 'reboot' command or restarting sbt.
    > set scala.version 2.7.3
     Build will use Scala 2.7.3 after running 'reboot' command or restarting sbt.
  • Fixed analysis plugin improperly including traits/abstract classes in subclass search. Previously, sbt would generate an error for the following project definition because it detected multiple publicly visible Project subclasses:
  •   trait ProjectHelper extends Project
      class MyProject(info: DefaultInfo) extends DefaultProject(info) with ProjectHelper
  • The launcher test loads a class from each of sbt, Ivy, the Scala compiler, and the Scala library to determine if jars were properly downloaded. Previously, it just tested if the right directory in project/boot existed.


  • Fixed  bug #19  ( always updated when using launcher)

sbt's Build

Building sbt from source in general has changed to support multiple Scala versions and the launcher. Please see Build for more information. Specific changes are:

  • The launcher project is now a proper subproject
  • The launcher now looks in the local Ivy repository for main sbt builder jars so that you can use jars compiled from source in your projects

Scala Jars and Dependency Management

sbt now checks and filters managed dependencies on Scala libraries, such as scala-library.jar and scala-compiler.jar.

Explicit Scala Dependencies

sbt checks that the revisions of any explicit dependencies on Scala libraries match that of the scala.version declared for the project. For example, sbt would generate an error if you defined scala.version to be 2.7.2 but had the following in your project definition:
 val scalaSwing = "org.scala-lang" % "scala-swing" % "2.7.3"

Filtering Scala Dependencies

sbt excludes all dependencies on scala-library.jar and scala-compiler.jar so that these will not be downloaded. sbt does this because it already provides the right versions of scala-library.jar and scala-compiler.jar required for normal use. If you do not ever need to explicitly reference these jars, this change should not affect you and you can stop reading this section now.

If you rely on either of these jars being in lib_managed, for example, you should use one of the following solutions:

  • The scalaJars method returns a two Files, one for the location of scala-compiler.jar and one for scala-library.jar.
  • mainCompileConditional.analysis.allExternals provides Files for all jars that your main classes depend on. This includes rt.jar, which you will probably want to filter.

Making Exceptions

sbt can be configured to skip these checks in certain cases, but this should be considered atypical. sbt's build does it in order to build sbt across several versions of Scala, but that is a bootstrapping issue. If you want to do this anyway, you should define a non-standard configuration and exclude it from the configurations on which sbt performs checks and filtering:

  val other = config("scalac-2.7.3")
  override def checkScalaInConfigurations = super.checkScalaInConfigurations - other
  val scalac2_7_3 = "org.scala-lang" % "scala-compiler" % "2.7.3" % "scalac-2.7.3->default"

You might then call java using the classpath given by managedClasspath("scalac-2.7.3"), for example.