With Scala 2.13 mockito-scala always treats `ArraySeq[_]` in last argument position as varags list

[seigert]

It could be reproduced with following Ammonite script:

import $ivy.{
  `org.mockito::mockito-scala-scalatest:1.16.15`,
  `org.scalatest::scalatest:3.2.3`,
  `org.scalatestplus::scalacheck-1-15:3.2.3.0`
}

import org.mockito.captor.{ ArgCaptor, Captor }
import org.mockito.scalatest.MockitoSugar
import org.scalatest.funspec.AnyFunSpec
import org.scalatest.matchers.should.Matchers

import scala.collection.immutable.ArraySeq

trait ArraySeqService {
  def testMethod(str: String, args: ArraySeq[String]): IndexedSeq[String]
}
trait IndexedSeqService {
  def testMethod(str: String, args: IndexedSeq[String]): IndexedSeq[String]
}

class MockitoSpec extends AnyFunSpec with Matchers with MockitoSugar {
  val arraySeq = mock[ArraySeqService]
  val indexedSeq = mock[IndexedSeqService]
  when {
    arraySeq.testMethod(any[String], any[ArraySeq[String]])
  }.thenAnswer[String, ArraySeq[String]] { (fst, rst) =>
    fst +: rst
  }
  when {
    indexedSeq.testMethod(any[String], any[IndexedSeq[String]])
  }.thenAnswer[String, IndexedSeq[String]] { (fst, rst) =>
    fst +: rst
  }
  describe("Mockito") {
    it("should allow ArraySeq as a last parameter") {
      arraySeq.testMethod("a", ArraySeq("b", "c")).should(contain).allOf("a", "b", "c")
    }
    it("should allow Vector as a last parameter to IndexedSeq method") {
      indexedSeq.testMethod("a", Vector("b", "c")).should(contain).allOf("a", "b", "c")
    }
    it("should allow ArraySeq as a last parameter to IndexedSeq method") {
      indexedSeq.testMethod("a", ArraySeq("b", "c")).should(contain).allOf("a", "b", "c")
    }
  }
}

(new MockitoSpec).execute()

What's worse, not only last parameters declared as ArraySeq is treated as part of vararg, but also when ArraySeq value passed to a parameter of 'plain' IndexedSeq type, it is also treated as a varargs list.

We think that code of org.mockito.internal.handler.unwrapVarags is a culprit here and some more sophisticated check should be perfomed.

[seigert]

@bbonanno, big thanks! 👍

[ultrasecreth]

@seigert no prob! thanks for the detailed report, it made it quite simpler to fix :)