How to (automatically) inherit settings/tasks from an sbt plugin? - scala

Question

I have an sbt plugin defining tasks that I would like to have available in a Play project, or another sbt project in general. While it might not be best practice, I'd prefer to have these tasks automatically available in the Play project, so that all I need to do is add the sbt plugin via plugins.sbt. But before I can even get that far, I'm having trouble importing tasks at all.
If the plugin's build.sbt is as follows:
name := "sbt-task-test"
version := "1.0.0-SNAPSHOT"
scalaVersion := "2.10.3"
scalaBinaryVersion := "2.10"
organization := "com.example"
sbtPlugin := true
lazy val testTask = taskKey[Unit]("Run a test task.")
testTask := {
println("Running test task..")
}
How can I make testTask available in another sbt project's build.sbt or Build.scala? I've tried following this example to no avail.
My end goal is to use tasks defined like in this blog post, but I'd like to at least get some simpler examples working first. In this case, I'd be adding something like registerTask("testTask", "com.example.tasks.Test", "Run a test task") to build.sbt, however I have the same problem as above.

Answer 1

First, you should put your task definition in the source of the plugin, not the build.sbt. So try this:
build.sbt of the plugin (it defines only how to build the plugin):
name := "sbt-task-test"
version := "1.0.0-SNAPSHOT"
scalaVersion := "2.10.3"
// scalaBinaryVersion := "2.10" // better not to play with this
organization := "com.example"
sbtPlugin := true
src/main/scala/MyPlugin.scala (in the plugin project)
import sbt._
object MyPlugin extends Plugin {
lazy val testTask = taskKey[Unit]("Run a test task.")
override def settings = Seq(
testTask := { println("Running test task..") }
)
}
Overriding settings helps to add the definition of this task to the project scope.
Now you should build and publish the plugin (locally for example) using sbt publishLocal.
Then in the project, where you want to use this plugin:
project/plugins.sbt should contain:
addSbtPlugin("com.example" % "sbt-task-test" % "1.0.0-SNAPSHOT")
This will add testTask key and definition to the scope automatically, so that you can do in the project's directory:
sbt testTask
and it will print Running test task..