FIX: KotlinDataClassComponent.getType() returned invalid raw type

databind/src/main/java/tech/ydb/yoj/databind/schema/reflect/KotlinDataClassComponent.java

@@ -1,7 +1,9 @@
 package tech.ydb.yoj.databind.schema.reflect;
 
+import com.google.common.reflect.TypeToken;
 import kotlin.jvm.JvmClassMappingKt;
 import kotlin.reflect.KCallable;
+import kotlin.reflect.KClass;
 import kotlin.reflect.jvm.KCallablesJvm;
 import kotlin.reflect.jvm.ReflectJvmMapping;
 import tech.ydb.yoj.databind.FieldValueType;
@@ -22,7 +24,7 @@ public final class KotlinDataClassComponent implements ReflectField {
     private final Class<?> type;
     private final FieldValueType valueType;
     private final Column column;
-    
+
     private final ReflectType<?> reflectType;
 
     public KotlinDataClassComponent(Reflector reflector, String name, KCallable<?> callable) {
@@ -33,7 +35,15 @@ public KotlinDataClassComponent(Reflector reflector, String name, KCallable<?> c
 
         var kReturnType = callable.getReturnType();
         this.genericType = ReflectJvmMapping.getJavaType(kReturnType);
-        this.type = JvmClassMappingKt.getJavaClass(kReturnType);
+
+        var kClassifier = kReturnType.getClassifier();
+        if (kClassifier instanceof KClass<?> kClass) {
+            this.type = JvmClassMappingKt.getJavaClass(kClass);
+        } else {
+            // fallback to Guava's TypeToken if kotlin-reflect returns unpredictable results ;-)
+            this.type = TypeToken.of(genericType).getRawType();
+        }
+
         this.column = type.getAnnotation(Column.class);
         this.valueType = FieldValueType.forJavaType(genericType, column);
         this.reflectType = reflector.reflectFieldType(genericType, valueType);

repository/pom.xml

@@ -39,6 +39,18 @@
             <artifactId>simpleclient</artifactId>
         </dependency>
 
+        <!-- Optional (Kotlin support) -->
+        <dependency>
+            <groupId>org.jetbrains.kotlin</groupId>
+            <artifactId>kotlin-reflect</artifactId>
+            <optional>true</optional>
+        </dependency>
+        <dependency>
+            <groupId>org.jetbrains.kotlin</groupId>
+            <artifactId>kotlin-stdlib</artifactId>
+            <optional>true</optional>
+        </dependency>
+
         <dependency>
             <groupId>org.eclipse.collections</groupId>
             <artifactId>eclipse-collections</artifactId>
@@ -70,4 +82,31 @@
             <scope>test</scope>
         </dependency>
     </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.jetbrains.kotlin</groupId>
+                <artifactId>kotlin-maven-plugin</artifactId>
+                <executions>
+                    <execution>
+                        <id>compileTests</id>
+                        <phase>process-test-sources</phase>
+                        <goals>
+                            <goal>test-compile</goal>
+                        </goals>
+                        <configuration>
+                            <sourceDirs>
+                                <source>src/test/java</source>
+                                <source>src/test/resources</source>
+                                <source>src/test/kotlin</source>
+                                <source>target/generated-sources/annotations</source>
+                            </sourceDirs>
+                            <jvmTarget>17</jvmTarget>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
 </project>

repository/src/test/java/tech/ydb/yoj/repository/hybrid/ChangeMetadata.java

@@ -0,0 +1,15 @@
+package tech.ydb.yoj.repository.hybrid;
+
+import java.time.Instant;
+
+public record ChangeMetadata(
+        ChangeKind kind,
+        Instant time,
+        long version
+) {
+    enum ChangeKind {
+        CREATE,
+        UPDATE,
+        DELETE,
+    }
+}

repository/src/test/java/tech/ydb/yoj/repository/hybrid/Chronology.java

@@ -0,0 +1,9 @@
+package tech.ydb.yoj.repository.hybrid;
+
+import java.time.Instant;
+
+public record Chronology(
+        Instant createdAt,
+        Instant updatedAt
+) {
+}

repository/src/test/kotlin/tech/ydb/yoj/repository/hybrid/Account.kt

@@ -0,0 +1,28 @@
+package tech.ydb.yoj.repository.hybrid
+
+import tech.ydb.yoj.repository.db.Entity
+
+data class Account(
+    private val id: Id,
+    private val version: Long,
+    private val chronology: Chronology,
+    val login: String,
+    val description: String? = null,
+) : Entity<Account> {
+    override fun getId() = id
+
+    data class Id(val value: String) : Entity.Id<Account>
+
+    data class Snapshot(
+        private val id: Id,
+        private val entity: Account?,
+        val meta: ChangeMetadata,
+    ) : Entity<Snapshot> {
+        override fun getId() = id
+
+        data class Id(
+            private val id: Account.Id,
+            private val version: Long
+        ) : Entity.Id<Snapshot>
+    }
+}

repository/src/test/kotlin/tech/ydb/yoj/repository/hybrid/HybridSchemaTest.kt

@@ -0,0 +1,45 @@
+package tech.ydb.yoj.repository.hybrid
+
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.Test
+import tech.ydb.yoj.repository.db.EntitySchema
+import java.time.Instant
+
+/**
+ * Test for Schema using both Kotlin data classes and JVM records.
+ */
+class HybridSchemaTest {
+    @Test
+    fun testIdFlattening() {
+        val now = Instant.now()
+        val account = Account(
+            id = Account.Id("hahaha"),
+            version = 1L,
+            chronology = Chronology(now, now),
+            login = "logIn",
+            description = null
+        )
+        val accountSnapshot = Account.Snapshot(
+            id = Account.Snapshot.Id(account.id, 1L),
+            entity = account,
+            meta = ChangeMetadata(ChangeMetadata.ChangeKind.CREATE, now, 1L)
+        )
+
+        val schema = EntitySchema.of(Account.Snapshot::class.java)
+
+        val flattened = schema.flatten(accountSnapshot)
+        assertThat(flattened).isEqualTo(mapOf(
+            "id_id" to "hahaha",
+            "id_version" to 1L,
+            "entity_id" to "hahaha",
+            "entity_version" to 1L,
+            "entity_chronology_createdAt" to now,
+            "entity_chronology_updatedAt" to now,
+            "entity_login" to "logIn",
+            "meta_kind" to ChangeMetadata.ChangeKind.CREATE,
+            "meta_time" to now,
+            "meta_version" to 1L
+        ))
+        assertThat(schema.newInstance(flattened)).isEqualTo(accountSnapshot)
+    }
+}