compiler crash when I use macros and playframework - scala

Question

I wrote a macro that parses JSON into a matching case class.
def parse(jsonTree: JsValue): BaseType = macro parserImpl
def parserImpl(c: blackbox.Context)(jsonTree: c.Tree) = {
import c.universe._
val q"$json" = jsonTree
val cases = List("X", "Y").map { caseClassName =>
val caseClass = c.parse(caseClassName)
val reader = c.parse(s"JSONHelp.${caseClassName}_reads")
val y = cq"""$caseClassName => (($json \ "config").validate[$caseClass]($reader)).get"""
println(showCode(y))
y
}.toList
val r =
q"""
import play.api.libs.json._
import JSONHelp._
println($json)
($json \ "type").as[String] match { case ..$cases }
"""
println(showCode(r))
r
}
The following is that code it generates (printed by the last println):
{
import play.api.libs.json._;
import JSONHelp._;
println(NodeParser.this.json);
NodeParser.this.json.\("type").as[String] match {
case "X" => NodeParser.this.json.\("config").validate[X](JSONHelp.X_reads).get
case "Y" => NodeParser.this.json.\("config").validate[Y](JSONHelp.Y_reads).get
}
}
The compilation of the subproject containing the macro definition works fine. But when I compile the project(using sbt 0.13.11 and scala 2.11.8) using the macro, I get the following error:
java.lang.NullPointerException
at play.routes.compiler.RoutesCompiler$GeneratedSource$.unapply(RoutesCompiler.scala:37)
at play.sbt.routes.RoutesCompiler$$anonfun$11$$anonfun$apply$2.isDefinedAt(RoutesCompiler.scala:180)
at play.sbt.routes.RoutesCompiler$$anonfun$11$$anonfun$apply$2.isDefinedAt(RoutesCompiler.scala:179)
at scala.Option.collect(Option.scala:250)
at play.sbt.routes.RoutesCompiler$$anonfun$11.apply(RoutesCompiler.scala:179)
at play.sbt.routes.RoutesCompiler$$anonfun$11.apply(RoutesCompiler.scala:178)

Answer 1

I'm not a user, but I see it seems to want tree positions with a source file:
val routesPositionMapper: Position => Option[Position] = position => {
position.sourceFile collect {
case GeneratedSource(generatedSource) => {
It's typical to use atPos(pos)(tree). You might assume the incoming tree.pos for synthetic trees.