Can't use Scala 2.11 -Ywarn-unused-import because it trips up the initialCommands

I’m trying to use the Scala 2.11 -Ywarn-unused-import option while compiling, but not in the console, where it effectively disables the ability to use most imports, especially in initialCommands.

Here’s a sample ./project/Build.scala file:

import sbt._
import sbt.Keys._

object MyBuild extends Build {
  import Resolvers._
  import BuildSettings._

  val commonScalacOptions = Vector("-deprecation", "-unchecked", "-feature",
        "-encoding", "utf8",
        "-Yno-adapted-args", "-Ywarn-dead-code",
        "-Ywarn-numeric-widen", "-Ywarn-value-discard")
  val compileScalacOptions = commonScalacOptions ++ Vector("-Ywarn-infer-any", "-Ywarn-unused-import")

  val scalaTest = "org.scalatest" %% "scalatest" % "2.2.1" % "test"

  lazy val myProject = Project(
    id = "SampleProject",
    base = file("."),
    settings = buildSettings ++ Seq(
      version      := "0.1.0",
      scalaVersion := "2.11.4",
      scalacOptions in Compile := compileScalacOptions,
      scalacOptions in console := commonScalacOptions,
      libraryDependencies ++= Seq(scalaTest)))
}

Here’s a sample ./build.sbt:

initialCommands += """
  import org.example.foo._
  """

Once I start sbt, I see the following:

> show *:console::scalacOptions
[info] Vector(-deprecation, -unchecked, -feature, -encoding, utf8, -Yno-adapted-args, -Ywarn-dead-code, -Ywarn-numeric-widen, -Ywarn-value-discard)
[success] Total time: 0 s, completed Jan 18, 2015 9:12:22 AM
> show compile:scalacOptions
[info] Vector(-deprecation, -unchecked, -feature, -encoding, utf8, -Yno-adapted-args, -Ywarn-dead-code, -Ywarn-numeric-widen, -Ywarn-value-discard, -Ywarn-infer-any, -Ywarn-unused-import)

But when I start the console, I get this:

> console
[info] Starting scala interpreter...
[info]
<console>:12: warning: Unused import
         import org.example.foo._
                                          ^
import org.example.foo._
Welcome to Scala version 2.11.4 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0).
...

It appears that the full set of compile options are being used. Using :power and :settings confirms this.

On the mailing list, someone suggested adding -Ywarn-unused-import:false to the scalacOptions in console. However, this appears to have no benefit.

[som-snytt]

It sure is nice having config in Scala, because if it compiles, it just works.

[dwijnand]

Warning no-ops aside, I think scalacOptions in console should do what it says on the tin.