build with config file

build.sbt

lazy val fetchConfFile = taskKey[File]("fetch Config file")
fetchConfFile := {
  //simulate fetching a remote file
  sLog.value.info("fetching file ...... ")
  Thread.sleep(1000)

  new java.io.File("/tmp/application.conf").createNewFile()
  val configFile : File = new java.io.File("/tmp/application.conf")
  sLog.value.info("done fetching file .... ")
  configFile

}
lazy val zip = taskKey[Unit]("zip files")

 zip := {
  val logger = sLog.value
  val fromZip: File = srcFile.value
  val toZip: File = baseDirectory.value / "build_and_config.zip"

   // we expect this to be run before the `fetchConfFile task
   // but this is actually run after
   logger.info(s"zipping files from ${fromZip.absolutePath}")

   //1.) calling .value actually executes this task
   //2.) sbt figures that the `zip task depends on the `fetchConfFile task
   //    so sbt actually runs the `fetchConfFile task before running the actual `zip task
   val configFile: File = fetchConfFile.value

   val filesToZip = List(configFile, fromZip)
   val fos        = new FileOutputStream(toZip)
   
   // zip function
   filesToZip.foldLeft(new ZipOutputStream(fos)){
     case (zs, file) =>
       val fis = new FileInputStream(file)
       val zipEntry = new ZipEntry(file.getName)
       zs.putNextEntry(zipEntry)

       @scala.annotation.tailrec
       def readAgain(c: Int): Int = {
         if (c < 0) {
           -1
         } else {
           zs.write(c)
           readAgain(fis.read())
         }
       }
     
       readAgain(fis.read())
       fis.close()
       zs
   }.close()
   
   logger.info(s"zipped files to ${toZip.absolutePath}")
 }