1 files changed, 96 insertions, 0 deletions
diff --git a/formats/json-tests/commonTest/src/kotlinx/serialization/json/JsonTreeAndMapperTest.kt b/formats/json-tests/commonTest/src/kotlinx/serialization/json/JsonTreeAndMapperTest.kt
new file mode 100644
index 00000000..336f630e
--- /dev/null
+++ b/formats/json-tests/commonTest/src/kotlinx/serialization/json/JsonTreeAndMapperTest.kt
@@ -0,0 +1,96 @@
+/*
+ * Copyright 2017-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ */
+
+package kotlinx.serialization.json
+
+import kotlinx.serialization.*
+import kotlinx.serialization.descriptors.*
+import kotlinx.serialization.encoding.*
+import kotlin.test.*
+
+class JsonTreeAndMapperTest {
+    private val decoderData = """{"id":0,"payload":{"from":42,"to":43,"msg":"Hello world"},"timestamp":1000}"""
+    private val decoderError = """{"id":1,"payload":{"error":"Connection timed out"},"timestamp":1001}"""
+
+    @Serializable
+    data class Payload(val from: Long, val to: Long, val msg: String)
+
+    sealed class Either {
+        data class Left(val errorMsg: String) : Either()
+        data class Right(val data: Payload) : Either()
+    }
+
+    object EitherSerializer : KSerializer<Either> {
+        override val descriptor: SerialDescriptor = buildSerialDescriptor("Either", PolymorphicKind.SEALED) {
+            val leftDescriptor = buildClassSerialDescriptor("Either.Left") {
+                element<String>("errorMsg")
+            }
+            val rightDescriptor = buildClassSerialDescriptor("Either.Right") {
+                element("data", Payload.serializer().descriptor)
+            }
+            element("left", leftDescriptor)
+            element("right", rightDescriptor)
+        }
+
+        override fun deserialize(decoder: Decoder): Either {
+            val input = decoder as? JsonDecoder ?: throw SerializationException("This class can be loaded only by Json")
+            val tree = input.decodeJsonElement() as? JsonObject
+                ?: throw SerializationException("Expected JsonObject")
+            if ("error" in tree) return Either.Left(tree.getValue("error").jsonPrimitive.content)
+
+            return Either.Right(input.json.decodeFromJsonElement(Payload.serializer(), tree))
+        }
+
+        override fun serialize(encoder: Encoder, value: Either) {
+            val output = encoder as? JsonEncoder ?: throw SerializationException("This class can be saved only by Json")
+            val tree = when (value) {
+                is Either.Left -> JsonObject(mapOf("error" to JsonPrimitive(value.errorMsg)))
+                is Either.Right -> output.json.encodeToJsonElement(Payload.serializer(), value.data)
+            }
+
+            output.encodeJsonElement(tree)
+        }
+    }
+
+    @Serializable
+    data class Event(
+        val id: Int,
+        @Serializable(with = EitherSerializer::class) val payload: Either,
+        val timestamp: Long
+    )
+
+    @Test
+    fun testParseData() {
+        val ev = Json.decodeFromString(Event.serializer(), decoderData)
+        with(ev) {
+            assertEquals(0, id)
+            assertEquals(Either.Right(Payload(42, 43, "Hello world")), payload)
+            assertEquals(1000, timestamp)
+        }
+    }
+
+    @Test
+    fun testParseError() {
+        val ev = Json.decodeFromString(Event.serializer(), decoderError)
+        with(ev) {
+            assertEquals(1, id)
+            assertEquals(Either.Left("Connection timed out"), payload)
+            assertEquals(1001, timestamp)
+        }
+    }
+
+    @Test
+    fun testWriteData() {
+        val encoderData = Event(0, Either.Right(Payload(42, 43, "Hello world")), 1000)
+        val ev = Json.encodeToString(Event.serializer(), encoderData)
+        assertEquals(decoderData, ev)
+    }
+
+    @Test
+    fun testWriteError() {
+        val encoderError = Event(1, Either.Left("Connection timed out"), 1001)
+        val ev = Json.encodeToString(Event.serializer(), encoderError)
+        assertEquals(decoderError, ev)
+    }
+}