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 Compile / run 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 Compile / run task and then open the browser for testing purposes.

src/main/scala/Greeting.scala 

object Greeting {
  def main(args: Array[String]): Unit = {
    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 := {
      (Compile / run).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 Compile / run:

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