SBT: Exclude class from Jar

Question

I am converting a legacy jar project to SBT and for strange reasons that are not easily solved, this project comes with \"javax/servlet/Servlet.class\" insi

Answer 1

I came up with this solution, it defines a new compile task which depends on the previous compile task (thus effectively allowing me to hook in right after the source is compiled and before it's packaged)

def mySettings = {
  // add functionality to the standard compile task 
  inConfig(Compile)(Seq(compile in Compile <<= (target,streams,compile in Compile) map{
    (targetDirectory, taskStream, analysis) =>
      import taskStream.log
      // this runs after compile but before package-bin
      recursiveListFiles(targetDirectory, ".*javax.*".r) foreach { 
        file =>
          log.warn("deleting matched resource: " + file.getAbsolutePath())
          IO.delete(file)
      }
      analysis
    })) ++
    Seq(name := "MyProject", version := "1.0", exportJars := true)
}

def recursiveListFiles(f: File, r: Regex): Array[File] = {
  val these = f.listFiles
  val good = these.filter(f => r.findFirstIn(f.getName).isDefined)
  good ++ these.filter(_.isDirectory).flatMap(recursiveListFiles(_, r))
}

Its a little bit more complicated than what I had hoped but it allows me to do all sorts of modifications prior to packaging (in this case searching the target folder deleting all class files that matches a regular expression). Also it accomplished my second goal of sticking with the default SBT lifecycle.