SBT create sub-projects using a collection - scala

Question

I've been searching if this is possible for a while with little success.
Using SBT, can you create a sub-project programmatically, without explicitly assigning each project to it's own val?
My current project structure looks something like this:
root/
common/ <--- This is another sub-project that others dependOn
project/
build.scala
src/main/scala
apps/ <--- sub-projects live here
Sub1/
Sub2/
Sub1 and Sub2 are both their own SBT projects.
My first attempt to link these projects together looked like this:
// root/project/build.scala
import sbt._
import Keys._
object build extends Build {
lazy val common = project /* Pseudo-code */
val names = List("Sub1", "Sub2")
lazy val deps = names map { name =>
Project(id = name, base = file(s"apps/$name")).dependsOn(common)
}
lazy val finalDeps = common :: deps
lazy val root = project.in(file(".")).aggregate(finalDeps.map(sbt.Project.projectToRef) :_*)
.dependsOn(finalDeps.map(ClassPathDependency(_, None)) :_*)
}
However, because SBT uses reflection to build it's projects and sub-projects, this doesn't work.
It only works if each sub-project is stated explicitly:
lazy val Sub1 = project.in(file("apps/Sub1"))
So the question:
Is there a way to programmatically build sub-project dependencies in SBT?

Answer 1

Sbt allows for making a build definition for the build itself:
http://www.scala-sbt.org/release/docs/Getting-Started/Full-Def.html
You can try creating a project/project/build.scala file that contains a source generator, something like this:
// project/project/build.scala
sourceGenerators in Compile <+= sourceManaged in Compile map { out =>
Generator.generate(out / "generated")
}
EDIT: You should implement the Generator object yourself.
This source generator will in turn scan the topmost apps folder and create a source for an object that contains all the subprojects.
// project/subprojects.scala
// This is autogenerated from the source generator
object Subprojects{
lazy val Sub1 = project.in(file("apps/Sub1"))
lazy val Sub2 = project.in(file("apps/Sub2"))
lazy val all = Seq(Sub1,Sub2)
}
Now in your main build.scala just write:
// project/build.scala
lazy val root = project.in(file("."))
.aggregate(Subprojects.all.map(sbt.Project.projectToRef) :_*)
.dependsOn(Subprojects.all.map(ClassPathDependency(_, None)) :_*)
I didn't run all this through a compiler so some errors are possible but the principle should work.
EDIT: I created a repo on Github where I implemented the solution. Go there and see how it is done.
https://github.com/darkocerdic/sbt-auto-subprojects