How to share version values between project/plugins.sbt and project/Build.scala?

Question

I would like to share a common version variable between an sbtPlugin and the rest of the build

Here is what I am trying:

in project/Build.scala:

Answer 1

My proposal is to hack. For example, in build.sbt you can add a task:

val readPluginSbt = taskKey[String]("Read plugins.sbt file.")

readPluginSbt := {
        val lineIterator = scala.io.Source.fromFile(new java.io.File("project","plugins.sbt")).getLines
            val linesWithValIterator = lineIterator.filter(line => line.contains("scalaxbVersion"))
            val versionString =  linesWithValIterator.mkString("\n").split("=")(1).trim
            val version = versionString.split("\n")(0) // only val declaration
        println(version)
        version
    }

When you call readPluginSbt you will see the contents of plugins.sbt. You can parse this file and extract the variable.

For example:

resolvers += Resolver.sonatypeRepo("public")

val scalaxbVersion = "1.1.2"

addSbtPlugin("org.scalaxb" % "sbt-scalaxb" % scalaxbVersion)

addSbtPlugin("org.xerial.sbt" % "sbt-pack" % "0.5.1")

You can extract scalaxbVersion with regular expressions/split:

scala> val line = """val scalaxbVersion = "1.1.2""""
line: String = val scalaxbVersion = "1.1.2"

scala>  line.split("=")(1).trim
res1: String = "1.1.2"