Update Kotlin [1.8.20 -> 2.0.21], compatible with Gradle 8.7 #215

Update coroutines to match, dokka to latest available version.

Author: greenrobot-team

.gitignore

@@ -13,6 +13,9 @@ target/
 out/
 classes/
 
+# Kotlin
+.kotlin
+
 # Local build properties
 build.properties
 local.properties

CHANGELOG.md

@@ -4,6 +4,10 @@ Notable changes to the ObjectBox Java library.
 
 For more insights into what changed in the ObjectBox C++ core, [check the ObjectBox C changelog](https://github.com/objectbox/objectbox-c/blob/main/CHANGELOG.md).
 
+## 4.3.1 - in development
+
+- Requires at least Kotlin compiler and standard library 1.7.
+
 ## 4.3.0 - 2025-05-13
 
 - Basic support for boolean array properties (`boolean[]` in Java or `BooleanArray` in Kotlin).

build.gradle.kts

@@ -52,14 +52,17 @@ buildscript {
     val essentialsVersion by extra("3.1.0")
     val junitVersion by extra("4.13.2")
     val mockitoVersion by extra("3.8.0")
-    // The versions of Kotlin, Kotlin Coroutines and Dokka must work together.
-    // Check https://github.com/Kotlin/kotlinx.coroutines#readme
-    // and https://github.com/Kotlin/dokka/releases
-    // Note: when updating might also have to increase the minimum compiler version supported
+    // The versions of Gradle, Kotlin and Kotlin Coroutines must work together.
+    // Check
+    // - https://kotlinlang.org/docs/gradle-configure-project.html#apply-the-plugin
+    // - https://github.com/Kotlin/kotlinx.coroutines#readme
+    // Note: when updating to a new minor version also have to increase the minimum compiler version supported
     // by consuming projects, see objectbox-kotlin/ build script.
-    val kotlinVersion by extra("1.8.20")
-    val coroutinesVersion by extra("1.7.3")
-    val dokkaVersion by extra("1.8.20")
+    val kotlinVersion by extra("2.0.21")
+    val coroutinesVersion by extra("1.9.0")
+    // Dokka includes its own version of the Kotlin compiler, so it must not match the used Kotlin version.
+    // But it might not understand new language features.
+    val dokkaVersion by extra("1.9.20")
 
     repositories {
         mavenCentral()

objectbox-kotlin/build.gradle.kts

@@ -23,8 +23,8 @@ tasks.withType<KotlinCompile> {
         // Kotlin supports the development with at least three previous versions, so pick the oldest one possible.
         // https://kotlinlang.org/docs/kotlin-evolution.html#evolving-the-binary-format
         // https://kotlinlang.org/docs/compatibility-modes.html
-        apiVersion = "1.5"
-        languageVersion = "1.5"
+        apiVersion = "1.7"
+        languageVersion = "1.7"
     }
 }
 

objectbox-rxjava3/build.gradle.kts

@@ -1,5 +1,5 @@
 import org.jetbrains.dokka.gradle.DokkaTask
-import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+import org.jetbrains.kotlin.gradle.dsl.JvmTarget
 import java.net.URL
 
 plugins {
@@ -15,10 +15,10 @@ tasks.withType<JavaCompile> {
     options.release.set(8)
 }
 
-// Produce Java 8 byte code, would default to Java 6.
-tasks.withType<KotlinCompile> {
-    kotlinOptions {
-        jvmTarget = "1.8"
+kotlin {
+    compilerOptions {
+        // Produce Java 8 byte code, would default to Java 6
+        jvmTarget.set(JvmTarget.JVM_1_8)
     }
 }
 

tests/objectbox-java-test/build.gradle.kts

@@ -1,5 +1,6 @@
 import org.gradle.api.tasks.testing.logging.TestExceptionFormat
 import org.gradle.api.tasks.testing.logging.TestLogEvent
+import org.jetbrains.kotlin.gradle.dsl.JvmTarget
 
 plugins {
     id("java-library")
@@ -12,10 +13,10 @@ tasks.withType<JavaCompile> {
     options.release.set(8)
 }
 
-// Produce Java 8 byte code, would default to Java 6.
-tasks.withType<org.jetbrains.kotlin.gradle.tasks.KotlinCompile> {
-    kotlinOptions {
-        jvmTarget = "1.8"
+kotlin {
+    compilerOptions {
+        // Produce Java 8 byte code, would default to Java 6
+        jvmTarget.set(JvmTarget.JVM_1_8)
     }
 }