1 files changed, 49 insertions, 0 deletions
diff --git a/formats/json-tests/commonTest/src/kotlinx/serialization/features/DerivedContextualSerializerTest.kt b/formats/json-tests/commonTest/src/kotlinx/serialization/features/DerivedContextualSerializerTest.kt
new file mode 100644
index 00000000..7da16fb8
--- /dev/null
+++ b/formats/json-tests/commonTest/src/kotlinx/serialization/features/DerivedContextualSerializerTest.kt
@@ -0,0 +1,49 @@
+package kotlinx.serialization.features
+
+import kotlin.test.*
+import kotlinx.serialization.*
+import kotlinx.serialization.descriptors.*
+import kotlinx.serialization.encoding.*
+import kotlinx.serialization.json.*
+import kotlinx.serialization.modules.*
+
+class DerivedContextualSerializerTest {
+
+    @Serializable
+    abstract class Message
+
+    @Serializable
+    class SimpleMessage(val body: String) : Message()
+
+    @Serializable
+    class Holder(@Contextual val message: Message)
+
+    object MessageAsStringSerializer : KSerializer<Message> {
+        override val descriptor: SerialDescriptor =
+            PrimitiveSerialDescriptor("kotlinx.serialization.MessageAsStringSerializer", PrimitiveKind.STRING)
+
+        override fun serialize(encoder: Encoder, value: Message) {
+            // dummy serializer that assumes Message is always SimpleMessage
+            check(value is SimpleMessage)
+            encoder.encodeString(value.body)
+        }
+
+        override fun deserialize(decoder: Decoder): Message {
+            return SimpleMessage(decoder.decodeString())
+        }
+    }
+
+    @Test
+    fun testDerivedContextualSerializer() {
+        val module = SerializersModule {
+            contextual(MessageAsStringSerializer)
+        }
+        val format = Json { serializersModule = module }
+        val data = Holder(SimpleMessage("hello"))
+        val serialized = format.encodeToString(data)
+        assertEquals("""{"message":"hello"}""", serialized)
+        val deserialized = format.decodeFromString<Holder>(serialized)
+        assertTrue(deserialized.message is SimpleMessage)
+        assertEquals("hello", deserialized.message.body)
+    }
+}