Doing something after an input task 

Thus far we’ve mostly looked at tasks. There’s another kind of tasks called input tasks that accepts user input from the shell. A typical example for this is the run in Compile task. The scalastyle task is actually an input task too. See input task for the details of the input tasks.

Now suppose we want to call run in Compile task and then open the browser for testing purposes.

src/main/scala/Greeting.scala 

object Greeting extends App {
  println("hello " + args.toList)
}

build.sbt v1 

lazy val runopen = inputKey[Unit]("run and then open the browser")

lazy val root = (project in file(".")).
  settings(
    runopen := {
      (run in Compile).evaluated
      println("open browser!")
    }
  )

Here, I’m faking the browser opening using println as the side effect. We can now call this task from the shell:

> runopen foo
[info] Compiling 1 Scala source to /x/proj/...
[info] Running Greeting foo
hello List(foo)
open browser!

build.sbt v2 

We can actually remove runopen key, by rewriting the new input task to run in Compile:

lazy val root = (project in file(".")).
  settings(
    run in Compile := {
      (run in Compile).evaluated
      println("open browser!")
    }
  )