sbt/notes/0.13.13.markdown

Fixes with compatibility implications

• Deprecates the old symbolic operators, to be removed in sbt 1.0. See below for more details.
• The .value method is deprecated for input tasks. Calling .value on an input key returns an InputTask[A], which is completely unintuitive and often results in a bug. In most cases .evaluated should be called, which returns A by evaluating the task. Just in case InputTask[A] is needed, .inputTaskValue method is now provided. #2709 by @eed3si9n
• sbt 0.13.13 renames the early command --<command> that was added in 0.13.1 to early(<command>). This fixes the regression #1041. For backward compatibility --error, --warn, --info, and --debug will continue to function during the 0.13 series, but it is strongly encouraged to migrate to the single hyphen options: -error, -warn, -info, and -debug. #2742 by @eed3si9n

Improvements

• Adds new command and templateResolvers. See below for more details.
• Auto plugins can add synthetic subprojects. See below for more details.
• Supports wildcard exclusions in POMs #1431/sbt/ivy#22/#2731 by @jtgrabowski
• Adds the ability to call aggregateProjects(..) for the current project inside a build sbt file. #2682 by @xuwei-k

Bug fixes

• Fixes a regression in sbt 0.13.12 that wrongly reports build-level keys to be ambiguous. #2707/#2708 by @Duhemm
• Fixes forked tests being reported as successful when the test harness fails. #2442/#2722/#2730 by @eed3si9n/@dwijnand

new command and templateResolvers

sbt 0.13.13 adds a new command, which helps create new build definitions. The new command is extensible via a mechanism called the template resolver, which evaluates the arguments passed to the command to find and run a template. As a reference implementation Giter8 is provided. For instance:

sbt new eed3si9n/hello.g8

will run eed3si9n/hello.g8 using Giter8.

#2705 by @eed3si9n

Synthetic subprojects

sbt 0.13.13 adds support for AutoPlugins to define subprojects programmatically, by overriding the extraProjects method:

import sbt._, Keys._

object ExtraProjectsPlugin extends AutoPlugin {
  override def extraProjects: Seq[Project] =
    List("foo", "bar", "baz") map generateProject

  def generateProject(id: String): Project =
    Project(id, file(id)).
      settings(
        name := id
      )
}

In addition, subprojects may be derived from an existing subproject by overriding derivedProjects:

import sbt._, Keys._

object DerivedProjectsPlugin extends AutoPlugin {
  // Enable this plugin by default
  override def requires: Plugins = sbt.plugins.CorePlugin
  override def trigger = allRequirements

  override def derivedProjects(proj: ProjectDefinition[_]): Seq[Project] =
    // Make sure to exclude project extras to avoid recursive generation
    if (proj.projectOrigin != ProjectOrigin.DerivedProject) {
      val id = proj.id + "1"
      Seq(
        Project(id, file(id)).
          enablePlugins(DatabasePlugin)
      )
    }
    else Nil
}

#2532/#2717/#2738 by @eed3si9n

Deprecate old operators

The no-longer-documented operators <<=, <+=, and <++= are deprecated, and will be removed in sbt 1.0.

For <<=, the suggested migration would be to use either := or ~= operators. The RHS of <<= takes an Initialize[_] expression, which can be converted to := style by wrapping the expression in parenthesis, and calling .value at the end. For example:

key := (key.dependsOn(compile in Test)).value

For <+= and <++=, use += { x.value } and ++= { x.value }.

#2716 by @eed3si9n