more work on deserializing null collections

Author: pjfanning

src/main/scala/tools/jackson/module/scala/deser/ImmutableBitSetDeserializer.scala

@@ -28,4 +28,11 @@ object ImmutableBitSetDeserializer extends StdDeserializer[immutable.BitSet](cla
     val elements = arrayNode.values().asScala.toSeq.map(_.asInt())
     immutable.BitSet(elements: _*)
   }
+
+  override def getEmptyValue(ctxt: DeserializationContext): immutable.BitSet =
+    immutable.BitSet.empty
+
+  override def getNullValue(ctxt: DeserializationContext): immutable.BitSet = {
+    getEmptyValue(ctxt)
+  }
 }

src/main/scala/tools/jackson/module/scala/deser/IntMapDeserializerResolver.scala

@@ -69,6 +69,8 @@ private[deser] object IntMapDeserializerResolver extends Deserializers.Base {
     }
 
     override def getEmptyValue(ctxt: DeserializationContext): Object = IntMap.empty[V]
+
+    override def getNullValue(ctxt: DeserializationContext): Object = getEmptyValue(ctxt)
   }
 
   private class IntMapInstantiator(config: DeserializationConfig, mapType: MapLikeType) extends StdValueInstantiator(config, mapType) {

src/main/scala/tools/jackson/module/scala/deser/LongMapDeserializerResolver.scala

@@ -75,6 +75,8 @@ private[deser] object LongMapDeserializerResolver extends Deserializers.Base {
     }
 
     override def getEmptyValue(ctxt: DeserializationContext): Object = immutable.LongMap.empty[V]
+
+    override def getNullValue(ctxt: DeserializationContext): Object = getEmptyValue(ctxt)
   }
 
   private class MutableLongMapDeserializer[V](mapType: MapLikeType, containerDeserializer: MapDeserializer)
@@ -105,6 +107,8 @@ private[deser] object LongMapDeserializerResolver extends Deserializers.Base {
     }
 
     override def getEmptyValue(ctxt: DeserializationContext): Object = mutable.LongMap.empty[V]
+
+    override def getNullValue(ctxt: DeserializationContext): Object = getEmptyValue(ctxt)
   }
 
   private class ImmutableLongMapInstantiator(config: DeserializationConfig, mapType: MapLikeType) extends StdValueInstantiator(config, mapType) {

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

@@ -72,6 +72,9 @@ object CaseClassDeserializerTest {
 
   case class ListHolder[T](list: List[T])
   case class AnnotatedListHolder[T](@JsonSetter(nulls = Nulls.AS_EMPTY)list: List[T])
+
+  case class MapHolder[K, V](map: Map[K, V])
+  case class AnnotatedMapHolder[K, V](@JsonSetter(nulls = Nulls.AS_EMPTY)map: Map[K, V])
 }
 
 class CaseClassDeserializerTest extends DeserializerTest {
@@ -211,4 +214,17 @@ class CaseClassDeserializerTest extends DeserializerTest {
     val result = deserialize(input, classOf[AnnotatedListHolder[String]])
     result.list shouldBe List.empty
   }
+
+  it should "support deserializing null input for map as empty map" in {
+    val input = """{}"""
+    val result = deserialize(input, classOf[MapHolder[Int, String]])
+    // this result has only happened since 3.0.0 - befpre result.map was null
+    result.map shouldBe Map.empty
+  }
+
+  it should "support deserializing null input for map as empty list (JsonSetter annotation)" in {
+    val input = """{}"""
+    val result = deserialize(input, classOf[AnnotatedMapHolder[Int, String]])
+    result.map shouldBe Map.empty
+  }
 }