NoSuchMethodError: scala.tools.nsc.Settings.usejavacp()Lscala/tools/nsc/settings/AbsSettings$AbsSetting;

Question

My code compiles against scala 2.12.10 but has to run on scala 2.12.15. My code:

import import scala.tools.nsc.Settings

val settings = new Settings
settings.usejavacp.value = false

usejavacp is throwing

java.lang.NoSuchMethodError: scala.tools.nsc.Settings.usejavacp()Lscala/tools/nsc/settings/AbsSettings$AbsSetting;

because Settings is a StandardScalaSettings where the definition of the class changed like so (only including relevant API):

2.12.10:

public interface scala.tools.nsc.settings.StandardScalaSettings {
  // other APIs
  public abstract scala.tools.nsc.settings.MutableSettings$BooleanSetting usejavacp();
}

to

2.12.15:

public interface scala.tools.nsc.settings.StandardScalaSettings {
  // other APIs
  public abstract scala.tools.nsc.settings.AbsSettings$AbsSetting usejavacp();
}

Is there any way I can make this work without upgrading my dependencies? Can I use reflection?

Answer 1

Yeah, runtime reflection works both in Scala 2.12.10 and 2.12.15.

You can replace

settings.usejavacp.value = false

with

import scala.reflect.runtime
import scala.reflect.runtime.universe._

val rm = runtime.currentMirror
val method = typeOf[MutableSettings].member(TermName("usejavacp")).asMethod
rm.reflect(settings).reflectMethod(method)().asInstanceOf[settings.BooleanSetting].value = false

Reflection to call method that had its name changed in an upgrade?

---

By the way, regarding your deleted question IncompatibleClassChangeError: org.apache.spark.sql.catalyst.plans.logical.LeafNode

You can try runtime compilation. It seems to work both in Spark 3.1.2 and 3.3.0.

// Spark 3.1.2

import scala.reflect.runtime.universe._
import scala.reflect.runtime
import scala.tools.reflect.ToolBox // libraryDependencies += scalaOrganization.value % "scala-compiler" % scalaVersion.value exclude("org.scala-lang.modules", "scala-xml_2.12")

object App {
  val rm = runtime.currentMirror
  val tb = rm.mkToolBox()
  val catalyst        = q"org.apache.spark.sql.catalyst"
  val Attribute       = tq"$catalyst.expressions.Attribute"
  val PredicateHelper = tq"$catalyst.expressions.PredicateHelper"
  val LeafNode        = tq"$catalyst.plans.logical.LeafNode"
  val sym = tb.define(
    q"""
      case class MyClass() extends $LeafNode with $PredicateHelper {
        override def output: Seq[$Attribute] = Seq()
      }
    """.asInstanceOf[ClassDef]
  ).asClass
}

// Spark 3.3.0

import scala.reflect.runtime.universe._

object Main {
  def main(args: Array[String]): Unit = {
    println(App.tb.eval(q"new ${App.sym}()")) // MyClass
  }
}