1 files changed, 72 insertions, 0 deletions
diff --git a/formats/json-tests/commonTest/src/kotlinx/serialization/features/MetaSerializableJsonTest.kt b/formats/json-tests/commonTest/src/kotlinx/serialization/features/MetaSerializableJsonTest.kt
new file mode 100644
index 00000000..af9ef6c2
--- /dev/null
+++ b/formats/json-tests/commonTest/src/kotlinx/serialization/features/MetaSerializableJsonTest.kt
@@ -0,0 +1,72 @@
+package kotlinx.serialization.features
+
+import kotlinx.serialization.*
+import kotlinx.serialization.json.*
+import kotlin.test.*
+
+@MetaSerializable
+@Target(AnnotationTarget.PROPERTY, AnnotationTarget.CLASS)
+annotation class JsonComment(val comment: String)
+
+@JsonComment("class_comment")
+data class IntDataCommented(val i: Int)
+
+class MetaSerializableJsonTest : JsonTestBase() {
+
+    @Serializable
+    data class Carrier(
+        val plain: String,
+        @JsonComment("string_comment") val commented: StringData,
+        val intData: IntDataCommented
+    )
+
+    class CarrierSerializer : JsonTransformingSerializer<Carrier>(serializer()) {
+
+        private val desc = Carrier.serializer().descriptor
+        private fun List<Annotation>.comment(): String? = filterIsInstance<JsonComment>().firstOrNull()?.comment
+
+        private val commentMap = (0 until desc.elementsCount).associateBy({ desc.getElementName(it) },
+            { desc.getElementAnnotations(it).comment() ?: desc.getElementDescriptor(it).annotations.comment() })
+
+        // NB: we may want to add this to public API
+        private fun JsonElement.editObject(action: (MutableMap<String, JsonElement>) -> Unit): JsonElement {
+            val mutable = this.jsonObject.toMutableMap()
+            action(mutable)
+            return JsonObject(mutable)
+        }
+
+        override fun transformDeserialize(element: JsonElement): JsonElement {
+            return element.editObject { result ->
+                for ((key, value) in result) {
+                    commentMap[key]?.let {
+                        result[key] = value.editObject {
+                            it.remove("comment")
+                        }
+                    }
+                }
+            }
+        }
+
+        override fun transformSerialize(element: JsonElement): JsonElement {
+            return element.editObject { result ->
+                for ((key, value) in result) {
+                    commentMap[key]?.let { comment ->
+                        result[key] = value.editObject {
+                            it["comment"] = JsonPrimitive(comment)
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    @Test
+    fun testMyJsonComment()  {
+        assertJsonFormAndRestored(
+            CarrierSerializer(),
+            Carrier("plain", StringData("string1"), IntDataCommented(42)),
+            """{"plain":"plain","commented":{"data":"string1","comment":"string_comment"},"intData":{"i":42,"comment":"class_comment"}}"""
+        )
+    }
+
+}