Fix Kotlin Serialization native support

extensions/resteasy-reactive/quarkus-resteasy-reactive-kotlin-serialization/deployment/src/main/java/io/quarkus/kotlin/serialization/deployment/KotlinSerializationProcessor.java

@@ -3,23 +3,55 @@
 import static io.quarkus.deployment.Feature.RESTEASY_REACTIVE_KOTLIN_SERIALIZATION;
 import static io.quarkus.resteasy.reactive.common.deployment.ServerDefaultProducesHandlerBuildItem.json;
 
+import java.util.ArrayList;
 import java.util.List;
 
 import javax.ws.rs.Priorities;
 import javax.ws.rs.RuntimeType;
 import javax.ws.rs.core.MediaType;
 
+import org.jboss.jandex.AnnotationInstance;
+import org.jboss.jandex.AnnotationTarget;
+import org.jboss.jandex.DotName;
+
 import io.quarkus.arc.deployment.AdditionalBeanBuildItem;
 import io.quarkus.deployment.annotations.BuildProducer;
 import io.quarkus.deployment.annotations.BuildStep;
+import io.quarkus.deployment.builditem.CombinedIndexBuildItem;
 import io.quarkus.deployment.builditem.FeatureBuildItem;
+import io.quarkus.deployment.builditem.nativeimage.ReflectiveClassBuildItem;
 import io.quarkus.kotlin.serialization.KotlinSerializationMessageBodyReader;
 import io.quarkus.kotlin.serialization.KotlinSerializationMessageBodyWriter;
 import io.quarkus.resteasy.reactive.common.deployment.ServerDefaultProducesHandlerBuildItem;
 import io.quarkus.resteasy.reactive.spi.MessageBodyReaderBuildItem;
 import io.quarkus.resteasy.reactive.spi.MessageBodyWriterBuildItem;
 
 public class KotlinSerializationProcessor {
+
+    private static final DotName SERIALIZABLE = DotName.createSimple("kotlinx.serialization.Serializable");
+    private static final String COMPANION_CLASS_SUFFIX = "$Companion";
+
+    // Kotlin Serialization generates classes at compile time which need to be available via reflection
+    // for serialization to work properly
+    @BuildStep
+    public void registerReflection(CombinedIndexBuildItem index, BuildProducer<ReflectiveClassBuildItem> reflectiveClass) {
+        var serializableInstances = index.getIndex().getAnnotations(SERIALIZABLE);
+        if (serializableInstances.isEmpty()) {
+            return;
+        }
+
+        List<String> supportClassNames = new ArrayList<>(2 * serializableInstances.size());
+        for (AnnotationInstance instance : serializableInstances) {
+            if (instance.target().kind() != AnnotationTarget.Kind.CLASS) {
+                continue;
+            }
+            var targetClass = instance.target().asClass().name();
+            String companionClassName = targetClass.toString() + COMPANION_CLASS_SUFFIX;
+            supportClassNames.add(companionClassName);
+        }
+        reflectiveClass.produce(new ReflectiveClassBuildItem(true, true, false, supportClassNames.toArray(new String[0])));
+    }
+
     @BuildStep
     public void additionalProviders(
             BuildProducer<AdditionalBeanBuildItem> additionalBean,

integration-tests/kotlin-serialization/pom.xml

@@ -119,12 +119,6 @@
                     </pluginOptions>
                 </configuration>
             </plugin>
-            <plugin>
-                <artifactId>maven-failsafe-plugin</artifactId>
-                <configuration>
-                    <skip>true</skip>
-                </configuration>
-            </plugin>
             <plugin>
                 <groupId>io.quarkus</groupId>
                 <artifactId>quarkus-maven-plugin</artifactId>

integration-tests/kotlin-serialization/src/main/kotlin/io/quarkus/it/kotser/model/Person.kt

@@ -1,10 +1,12 @@
 package io.quarkus.it.kotser.model
 
+import io.quarkus.runtime.annotations.RegisterForReflection
 import kotlinx.serialization.Serializable
 
 @Serializable
+@RegisterForReflection
 data class Person(var name: String, var defaulted: String = "hi there!") {
     override fun toString(): String {
         TODO("this shouldn't get called. a proper serialization should be invoked.")
     }
-}
+}

integration-tests/kotlin-serialization/src/test/kotlin/io/quarkus/it/kotser/ResourceIT.kt

@@ -0,0 +1,7 @@
+package io.quarkus.it.kotser
+
+import io.quarkus.test.junit.QuarkusIntegrationTest
+
+@QuarkusIntegrationTest
+class ResourceIT : ResourceTest() {
+}

integration-tests/kotlin-serialization/src/test/kotlin/io/quarkus/it/kotser/ResourceTest.kt

@@ -7,7 +7,7 @@ import org.hamcrest.CoreMatchers.`is`
 import org.junit.jupiter.api.Test
 
 @QuarkusTest
-class ResourceTest {
+open class ResourceTest {
     @Test
     fun testGet() {
         given()
@@ -37,4 +37,4 @@ class ResourceTest {
                   "defaulted": "hi there!"
                 }""".trimIndent()))
     }
-}
+}