1 files changed, 139 insertions, 0 deletions
diff --git a/formats/json-tests/commonTest/src/kotlinx/serialization/SerializerForNullableTypeTest.kt b/formats/json-tests/commonTest/src/kotlinx/serialization/SerializerForNullableTypeTest.kt
new file mode 100644
index 00000000..98f3f5e0
--- /dev/null
+++ b/formats/json-tests/commonTest/src/kotlinx/serialization/SerializerForNullableTypeTest.kt
@@ -0,0 +1,139 @@
+/*
+ * Copyright 2017-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ */
+
+package kotlinx.serialization
+
+import kotlinx.serialization.descriptors.*
+import kotlinx.serialization.encoding.*
+import kotlinx.serialization.json.*
+import kotlinx.serialization.test.*
+import kotlin.test.*
+
+public class SerializerForNullableTypeTest : JsonTestBase() {
+
+    // Nullable boxes
+    @Serializable(with = StringHolderSerializer::class)
+    data class StringHolder(val s: String)
+
+    object StringHolderSerializer : KSerializer<StringHolder?> {
+        override val descriptor: SerialDescriptor = PrimitiveSerialDescriptor("SHS", PrimitiveKind.STRING).nullable
+
+        override fun serialize(encoder: Encoder, value: StringHolder?) {
+            if (value == null) encoder.encodeString("nullable")
+            else encoder.encodeString("non-nullable")
+        }
+
+        override fun deserialize(decoder: Decoder): StringHolder? {
+            if (decoder.decodeNotNullMark()) {
+                return StringHolder("non-null: " + decoder.decodeString())
+            }
+            decoder.decodeNull()
+            return StringHolder("nullable")
+        }
+    }
+
+    @Serializable
+    data class Box(val s: StringHolder?)
+
+    @Test
+    fun testNullableBoxWithNotNull() {
+        val b = Box(StringHolder("box"))
+        val string = Json.encodeToString(b)
+        assertEquals("""{"s":"non-nullable"}""", string)
+        val deserialized = Json.decodeFromString<Box>(string)
+        assertEquals(Box(StringHolder("non-null: non-nullable")), deserialized)
+    }
+
+    @Test
+    fun testNullableBoxWithNull() {
+        val b = Box(null)
+        val string = Json.encodeToString(b)
+        assertEquals("""{"s":"nullable"}""", string)
+        val deserialized = Json.decodeFromString<Box>(string)
+        assertEquals(Box(StringHolder("non-null: nullable")), deserialized)
+    }
+
+    @Test
+    fun testNullableBoxDeserializeNull() {
+        val deserialized = Json.decodeFromString<Box>("""{"s":null}""")
+        assertEquals(Box(StringHolder("nullable")), deserialized)
+    }
+
+    // Nullable primitives
+    object NullableLongSerializer : KSerializer<Long?> {
+
+        @Serializable
+        data class OptionalLong(val initialized: Boolean, val value: Long? = 0)
+
+        override val descriptor: SerialDescriptor = buildClassSerialDescriptor("NLS") {
+            element<Boolean>("initialized")
+            element<Long?>("value")
+        }.nullable
+
+        override fun serialize(encoder: Encoder, value: Long?) {
+            val opt = OptionalLong(value != null, value)
+            encoder.encodeSerializableValue(OptionalLong.serializer(), opt)
+        }
+
+        override fun deserialize(decoder: Decoder): Long? {
+            val value = decoder.decodeSerializableValue(OptionalLong.serializer())
+            return if (value.initialized) value.value else null
+        }
+    }
+
+    @Serializable
+    data class NullablePrimitive(
+        @Serializable(with = NullableLongSerializer::class) val value: Long?
+    )
+
+    @Test
+    fun testNullableLongWithNotNull() {
+        val data = NullablePrimitive(42)
+        val json = Json.encodeToString(data)
+        assertEquals("""{"value":{"initialized":true,"value":42}}""", Json.encodeToString(data))
+        assertEquals(data, Json.decodeFromString(json))
+    }
+
+    @Test
+    fun testNullableLongWithNull() {
+        val data = NullablePrimitive(null)
+        val json = Json.encodeToString(data)
+        assertEquals("""{"value":{"initialized":false,"value":null}}""", Json.encodeToString(data))
+        assertEquals(data, Json.decodeFromString(json))
+    }
+
+    // Now generics
+    @Serializable
+    data class GenericNullableBox<T: Any>(val value: T?)
+
+    @Serializable
+    data class GenericBox<T>(val value: T?)
+
+    @Test
+    fun testGenericBoxNullable() {
+        val data = GenericBox<StringHolder?>(null)
+        val json = Json.encodeToString(data)
+        assertEquals("""{"value":"nullable"}""", Json.encodeToString(data))
+        assertEquals(GenericBox(StringHolder("non-null: nullable")), Json.decodeFromString(json))
+    }
+
+    @Test
+    fun testGenericNullableBoxFromNull() {
+        assertEquals(GenericBox(StringHolder("nullable")), Json.decodeFromString("""{"value":null}"""))
+    }
+
+    @Test
+    fun testGenericNullableBoxNullable() {
+        val data = GenericNullableBox<StringHolder>(null)
+        val json = Json.encodeToString(data)
+        assertEquals("""{"value":"nullable"}""", Json.encodeToString(data))
+        assertEquals(GenericNullableBox(StringHolder("non-null: nullable")), Json.decodeFromString(json))
+    }
+
+    @Test
+    fun testGenericBoxNullableFromNull() {
+        assertEquals(GenericNullableBox(StringHolder("nullable")), Json.decodeFromString("""{"value":null}"""))
+    }
+
+}