How to declare subproject dependency from another project?

Question

I have two projects A and B in sibling directories. I know I can make A depend on B using RootProject:

object A extends Build {
  lazy val A = project in file(".") dependsOn(B)
  lazy val B = RootProject(file("../B"))
}

But B includes two core and extensions subprojects, and I want to depend on core only. Is this possible?

Answer 1

The answer turns out to be given at SBT dependsOn RootProject: doesn't compile the dependency:

lazy val BCore = ProjectRef(file("../B"), "core")