SBT InputKey with property-like arguments - scala

Question

Can someone help me create a SBT task that can support property-like arguments from command line?
lazy val myTask = inputKey[Unit]("my task")
myTask := {
if (directoryOpt.isEmpty) // directoryOpt comes from an optional command line argument: directory="~/downloads"
fullRunInputTask(inputKey, Compile, "example.MyTaskClass")
else
fullRunInputTask(inputKey, Compile, "example.MyTaskClass", directoryOpt.get)
}
Where the task can be run from command line like:
sbt myTask directory="~/downloads"
I did read the sbt doc at http://www.scala-sbt.org/0.13/docs/Input-Tasks.html. But it only explains how to create a task parser like sbt myTask option1 option2 which does not quite meet my need.
UPDATE:
I used jazmit's solution since that was an easy change. It works well! I will also try Mariusz's solution and update here.

Answer 1

You can use project/Build.scala along your build.sbt with your inputs. You can also use Commands instead of Tasks. Below, an example:
import sbt._
import Keys._
object CustomBuild extends Build {
def myTask = Command.args("myTask", "<name>"){ (state, args) =>
val argMap = args.map { s =>
s.split("=").toList match {
case n :: v :: Nil => n -> v
}
}.toMap
//println(argMap) //to see all argument pairs
//react on name in params list
println("Hi "+ argMap.getOrElse("name", "Unknown"))
state //Command can modify state, so you must to return it.
}
}
Now You have to add this command to you project, in build.sbt add
commands += myTask
Now you can use it:
> sbt "myTask name=Mario"
> Hi Mario
> sbt myTask
> sbt Hi Unknown
Hope, it'll help You!
more about commands:
you can find here

Answer 2

You can use environmental properties to achieve what you want quickly.
From the command line, set a property as follows:
sbt myTask -Ddirectory="~/downloads"
From the task, you can retrieve the value as follows:
val directory = System.getProperty("directory");
If you want to do something more solid with syntax checking, tab completion, etc, you can define an input task as detailed here. If you need property=value syntax, you can define this using the parser combinator library, eg:
import sbt.complete.DefaultParsers._
val myArgs: Parser[String] = "directory=" ~> StringEscapable