ReturnsSmartNulls.scala

package org.mockito
package stubbing
import java.lang.reflect.Modifier.isFinal
import org.mockito.Mockito.{ mock, withSettings }
import org.mockito.internal.debugging.LocationFactory
import org.mockito.internal.exceptions.Reporter.smartNullPointerException
import org.mockito.internal.stubbing.defaultanswers.ReturnsMoreEmptyValues
import org.mockito.internal.util.ObjectMethodsGuru.isToStringMethod
import org.mockito.invocation.{ InvocationOnMock, Location }

object ReturnsSmartNulls extends DefaultAnswer {
  val delegate = new ReturnsMoreEmptyValues

  override def apply(invocation: InvocationOnMock): Option[Any] =
    Option(delegate.answer(invocation)).orElse {
      val returnType = invocation.returnType

      if (!returnType.isPrimitive && !isFinal(returnType.getModifiers) && classOf[Object] != returnType)
        Some(mock(returnType, withSettings.defaultAnswer(ThrowsSmartNullPointer(invocation)).lenient()))
      else
        None
    }

  case class ThrowsSmartNullPointer(unstubbedInvocation: InvocationOnMock, location: Location = LocationFactory.create()) extends Answer[AnyRef] {
    override def answer(invocation: InvocationOnMock): AnyRef =
      if (isToStringMethod(invocation.getMethod))
        s"""SmartNull returned by this unstubbed method call on a mock:
           |$unstubbedInvocation""".stripMargin
      else
        throw smartNullPointerException(unstubbedInvocation.toString, location)
  }
}