add deser tests for empty lists

Author: pjfanning

src/test/scala/tools/jackson/module/scala/deser/CaseClassDeserializerTest.scala

@@ -1,6 +1,6 @@
 package tools.jackson.module.scala.deser
 
-import com.fasterxml.jackson.annotation.JsonProperty
+import com.fasterxml.jackson.annotation.{JsonProperty, JsonSetter, Nulls}
 import tools.jackson.databind.annotation.JsonDeserialize
 import tools.jackson.databind.exc.MismatchedInputException
 import tools.jackson.databind.json.JsonMapper
@@ -69,6 +69,9 @@ object CaseClassDeserializerTest {
   class NestedB(id: Int) {
     def x = id
   }
+
+  case class ListHolder[T](list: List[T])
+  case class AnnotatedListHolder[T](@JsonSetter(nulls = Nulls.AS_EMPTY)list: List[T])
 }
 
 class CaseClassDeserializerTest extends DeserializerTest {
@@ -195,4 +198,16 @@ class CaseClassDeserializerTest extends DeserializerTest {
     val result = deserialize(input, classOf[ClassWithOnlyUnitField])
     result shouldEqual ClassWithOnlyUnitField(())
   }
+
+  it should "support deserializing null input for list as empty list" ignore {
+    val input = """{}"""
+    val result = deserialize(input, classOf[ListHolder[String]])
+    result.list shouldBe null // ideally should be empty list, Scala users expect no nulls
+  }
+
+  it should "support deserializing null input for list as empty list (JsonSetter annotation)" in {
+    val input = """{}"""
+    val result = deserialize(input, classOf[AnnotatedListHolder[String]])
+    result.list shouldBe List.empty
+  }
 }