Implementation in Converter, replacing Serializer

Related to FasterXML#671, FasterXML#674.

Author: k163377

src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt

@@ -1,9 +1,21 @@
 package com.fasterxml.jackson.module.kotlin
 
+import com.fasterxml.jackson.databind.JavaType
 import com.fasterxml.jackson.databind.ser.std.StdDelegatingSerializer
+import com.fasterxml.jackson.databind.type.TypeFactory
 import com.fasterxml.jackson.databind.util.StdConverter
 import kotlin.reflect.KClass
 
+internal class SequenceToIteratorConverter(private val input: JavaType) : StdConverter<Sequence<*>, Iterator<*>>() {
+    override fun convert(value: Sequence<*>): Iterator<*> = value.iterator()
+
+    override fun getInputType(typeFactory: TypeFactory): JavaType = input
+    // element-type may not be obtained, so a null check is required
+    override fun getOutputType(typeFactory: TypeFactory): JavaType = input.containedType(0)
+        ?.let { typeFactory.constructCollectionLikeType(Iterator::class.java, it) }
+        ?: typeFactory.constructType(Iterator::class.java)
+}
+
 // S is nullable because value corresponds to a nullable value class
 // @see KotlinNamesAnnotationIntrospector.findNullSerializer
 internal class ValueClassBoxConverter<S : Any?, D : Any>(

src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinAnnotationIntrospector.kt

@@ -64,9 +64,17 @@ internal class KotlinAnnotationIntrospector(private val context: Module.SetupCon
         return super.findCreatorAnnotation(config, a)
     }
 
-    // Find a converter to handle the case where the getter returns an unboxed value from the value class.
-    override fun findSerializationConverter(a: Annotated): Converter<*, *>? = (a as? AnnotatedMethod)?.let { _ ->
-        cache.findValueClassReturnType(a)?.let { cache.getValueClassBoxConverter(a.rawReturnType, it) }
+    override fun findSerializationConverter(a: Annotated): Converter<*, *>? = when (a) {
+        // Find a converter to handle the case where the getter returns an unboxed value from the value class.
+        is AnnotatedMethod -> cache.findValueClassReturnType(a)
+            ?.let { cache.getValueClassBoxConverter(a.rawReturnType, it) }
+            ?: a.takeIf { Sequence::class.java.isAssignableFrom(it.rawType) }
+                ?.let { SequenceToIteratorConverter(it.type) }
+
+        is AnnotatedClass -> a
+            .takeIf { Sequence::class.java.isAssignableFrom(it.rawType) }
+            ?.let { SequenceToIteratorConverter(it.type) }
+        else -> null
     }
 
     // Determine if the unbox result of value class is nullAable

src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinSerializers.kt

@@ -13,12 +13,6 @@ import java.lang.reflect.Method
 import java.lang.reflect.Modifier
 import java.math.BigInteger
 
-object SequenceSerializer : StdSerializer<Sequence<*>>(Sequence::class.java) {
-    override fun serialize(value: Sequence<*>, gen: JsonGenerator, provider: SerializerProvider) {
-        provider.defaultSerializeValue(value.iterator(), gen)
-    }
-}
-
 object UByteSerializer : StdSerializer<UByte>(UByte::class.java) {
     override fun serialize(value: UByte, gen: JsonGenerator, provider: SerializerProvider) =
         gen.writeNumber(value.toShort())
@@ -98,7 +92,6 @@ internal class KotlinSerializers : Serializers.Base() {
         val rawClass = type.rawClass
 
         return when {
-            Sequence::class.java.isAssignableFrom(rawClass) -> SequenceSerializer
             UByte::class.java.isAssignableFrom(rawClass) -> UByteSerializer
             UShort::class.java.isAssignableFrom(rawClass) -> UShortSerializer
             UInt::class.java.isAssignableFrom(rawClass) -> UIntSerializer