How to make a sbt task use a specific configuration scope?

Question

I have a task lazy val task = TaskKey[Unit] that takes a lazy val setting = SettingKey[String] as input. I also have three different, independent c

Answer 1

I think you need to write something like

val devTaskSetting = task <<= setting in dev map { s: String =>
   println("Setting in Dev is: " + s)
}

You can also define separate task keys, like this

val devTask   = TaskKey[Unit]("task", "a simple task experiment") in dev
val stageTask = TaskKey[Unit]("task", "a simple task experiment") in stage

Answer 2

As discussed in How can i make an SBT key see settings for the current configuration?, you can probably use inConfig as follows.

Change this:

settings = Defaults.defaultSettings ++ Seq(taskTask)

to this:

settings = Defaults.defaultSettings ++
  Seq(taskTask) ++
  inConfig(dev)(Seq(taskTask)) ++
  inConfig(stage)(Seq(taskTask)) ++
  inConfig(prod)(Seq(taskTask))

and voilà:

$ sbt
> task
Setting is: default setting
> dev:task
Setting is: default setting
> stage:task
Setting is: stage setting
> prod:task
Setting is: prod setting

If you're interested in digging deeper, inConfig is defined in sbt.Project ( http://harrah.github.io/xsbt/latest/api/index.html#sbt.Project$ ) as a function to "copy a subgraph of tasks/settings into different scopes" (as @MarkHarrah describes it). Also, take a look at http://eed3si9n.com/sbt-010-guide and scroll down to "changing the scopes" where the author explains how inConfig(conf)(ss) "scopes the settings ss in to conf only when it isn't scoped yet to a configuration".