Configurations
Wiki Maintenance Note: Most of what's on this page is now covered in Getting Started Library Dependencies. This page should be analyzed for any points that aren't covered on the new page, and those points moved somewhere (maybe the FAQ or an "advanced library deps" page). Then this page could become a redirect with no content except a link pointing to the new page(s).
Wiki Maintenance Note 2: There probably should be a page called Configurations that's less about library dependency management and more about listing all the configurations that exist and describing what they are used for. This would complement the way this page is linked, for example in Index.
Ivy configurations are a useful feature for your build when you use managed dependencies. They are essentially named sets of dependencies. You can read the Ivy documentation for details. Their use in sbt is described on this page.
The built-in use of configurations in sbt is similar to scopes in Maven. sbt adds dependencies to different classpaths by the configuration that they are defined in. See the description of Maven Scopes for details.
You put a dependency in a configuration by selecting one or more of its configurations to map to one or more of your project's configurations. The most common case is to have one of your configurations A use a dependency's configuration B. The mapping for this looks like "A->B". To apply this mapping to a dependency, add it to the end of your dependency definition:
libraryDependencies += "org.scalatest" % "scalatest" % "1.2" % "test->compile"This says that your project's test configuration uses ScalaTest's default configuration. Again, see the Ivy documentation for more advanced mappings. Most projects published to Maven repositories will use the default or compile configuration.
A useful application of configurations is to group dependencies that are not used on normal classpaths. For example, your project might use a "js" configuration to automatically download jQuery and then include it in your jar by modifying resources. For example:
ivyConfigurations += config("js") hide
libraryDependencies += "jquery" % "jquery" % "1.3.2" % "js->default" from "http://jqueryjs.googlecode.com/files/jquery-1.3.2.min.js"
resources <<= (resources, update) { (rs, report) =>
rs ++ report.select( configurationFilter("js") )
}The config method defines a new configuration with name "js" and makes it private to the project so that it is not used for publishing.
See Update Report for more information on selecting managed artifacts.
A configuration without a mapping (no "->") is mapped to default or compile. The -> is only needed when mapping to a different configuration than those. The ScalaTest dependency above can then be shortened to:
libraryDependencies += "org.scala-tools.testing" % "scalatest" % "1.0" % "test"