Why does custom scaladoc task throw MissingRequirementError: object scala.annotation.Annotation in compiler mirror not found? - scala

Question

I hit a MissingRequirementError when I try to invoke scaladoc from within an sbt task.
Using any version of sbt 0.13.x, start with this build.sbt:
val scaladoc = taskKey[Unit]("run scaladoc")
scaladoc := {
import scala.tools.nsc._
val settings = new doc.Settings(error => print(error))
settings.usejavacp.value = true
val docFactory = new doc.DocFactory(new reporters.ConsoleReporter(settings), settings)
val universe = docFactory.makeUniverse(Left((sources in Compile).value.map(_.absolutePath).toList))
}
Then run sbt scaladoc, and behold (during makeUniverse):
[info] Set current project to test (in build file:...)
scala.reflect.internal.MissingRequirementError: object scala.annotation.Annotation in compiler mirror not found.
at scala.reflect.internal.MissingRequirementError$.signal(MissingRequirementError.scala:16)
at scala.reflect.internal.MissingRequirementError$.notFound(MissingRequirementError.scala:17)
at scala.reflect.internal.Mirrors$RootsBase.getModuleOrClass(Mirrors.scala:48)
What is wrong here? I've already tried fork := true and different combinations of sbt/scala versions to no avail.

Answer 1

It seems you need to provide scala-library (and indeed, any other dependencies) directly to the DocFactory.
scaladoc := {
import scala.tools.nsc._
val settings = new doc.Settings(error => print(error))
val dependencyPaths = (update in Compile).value
.select().map(_.absolutePath).mkString(java.io.File.pathSeparator)
settings.classpath.append(dependencyPaths)
settings.bootclasspath.append(dependencyPaths)
val docFactory = new doc.DocFactory(new reporters.ConsoleReporter(settings), settings)
val universe = docFactory.makeUniverse(Left((sources in Compile).value.map(_.absolutePath).toList))
}