add tests to show nullable Json{Element,Primitive,Null} decoding works

Kotlin · Sep 29, 2023 · b709c0d · b709c0d
1 parent 99e3f91
commit b709c0d
Showing 1 changed file with 57 additions and 1 deletion.
diff --git a/formats/json-tests/commonTest/src/kotlinx/serialization/json/JsonElementDecodingTest.kt b/formats/json-tests/commonTest/src/kotlinx/serialization/json/JsonElementDecodingTest.kt
@@ -1,6 +1,8 @@
 package kotlinx.serialization.json
 
-import kotlinx.serialization.Serializable
+import kotlinx.serialization.*
+import kotlinx.serialization.descriptors.*
+import kotlinx.serialization.encoding.*
 import kotlin.test.*
 
 class JsonElementDecodingTest : JsonTestBase() {
@@ -51,4 +53,58 @@ class JsonElementDecodingTest : JsonTestBase() {
         json = json.replace("%", "0")
         Json.parseToJsonElement(json)
     }
+
+    private open class NullableSerializer<T : Any>(private val serializer: KSerializer<T>) : KSerializer<T?> {
+        final override val descriptor: SerialDescriptor = serializer.descriptor.nullable
+
+        final override fun serialize(encoder: Encoder, value: T?) {
+            if (value == null) {
+                encoder.encodeNull()
+            } else {
+                serializer.serialize(encoder, value)
+            }
+        }
+
+        final override fun deserialize(decoder: Decoder): T = serializer.deserialize(decoder)
+    }
+
+    private object NullableJsonElementSerializer : NullableSerializer<JsonElement>(JsonElement.serializer())
+    private object NullableJsonPrimitiveSerializer : NullableSerializer<JsonPrimitive>(JsonPrimitive.serializer())
+    private object NullableJsonNullSerializer : NullableSerializer<JsonNull>(JsonNull.serializer())
+
+    @Test
+    fun testNullableJsonElementDecoding() {
+        @Serializable
+        data class Wrapper(
+            @Serializable(NullableJsonElementSerializer::class)
+            val value: JsonElement? = null,
+        )
+
+        assertSerializedForm<Wrapper>(Wrapper(value = JsonNull), """{"value":null}""")
+        assertSerializedForm<Wrapper>(Wrapper(value = null), """{}""")
+    }
+
+    @Test
+    fun testNullableJsonPrimitiveDecoding() {
+        @Serializable
+        data class Wrapper(
+            @Serializable(NullableJsonPrimitiveSerializer::class)
+            val value: JsonPrimitive? = null,
+        )
+
+        assertSerializedForm<Wrapper>(Wrapper(value = JsonNull), """{"value":null}""")
+        assertSerializedForm<Wrapper>(Wrapper(value = null), """{}""")
+    }
+
+    @Test
+    fun testNullableJsonNullDecoding() {
+        @Serializable
+        data class Wrapper(
+            @Serializable(NullableJsonNullSerializer::class)
+            val value: JsonNull? = null,
+        )
+
+        assertSerializedForm<Wrapper>(Wrapper(value = JsonNull), """{"value":null}""")
+        assertSerializedForm<Wrapper>(Wrapper(value = null), """{}""")
+    }
 }