Downgrade Kotlin to 2.1.21

- Downgrade Kotlin 2.2.0->2.1.21 to make broader adoption possible. Update Kotlin compiler configuration
- Add [kotlinx-datetime](https://github.com/Kotlin/kotlinx-datetime) dependency. Switch from `kotlin.time.Instant` to `kotlinx.datetime.Instant`.
- Downgrade atomicfu 0.29.0->0.28.0
- Downgrade kotlinx-serialization 1.9.0->1.8.1

Author: kpavlov

CONTRIBUTING.md

@@ -73,6 +73,8 @@ See [How to Write a Git Commit Message](https://chris.beams.io/posts/git-commit/
 
 * To build MCP Kotlin SDK, JDK version 21 or higher is required. Make sure this is your default JDK (`JAVA_HOME` is set
   accordingly)
+* To build for MacOS/iOS targets, Xcode/Command Line Tools should be installed. See Apple Developer [documentation](https://developer.apple.com/documentation/xcode/downloading-and-installing-additional-xcode-components) for details.
+* To build JS/Wasm targets, [Node.js](https://nodejs.org/) must be installed.
 * The project can be opened in IntelliJ IDEA without additional prerequisites.
 
 ### Building MCP Kotlin SDK from source

README.md

@@ -1,7 +1,8 @@
 # MCP Kotlin SDK
 
+[![Kotlin](https://img.shields.io/badge/kotlin-2.1-blue.svg?logo=kotlin)](http://kotlinlang.org)
 [![Kotlin Multiplatform](https://img.shields.io/badge/Kotlin-Multiplatform-blueviolet?logo=kotlin)](https://kotlinlang.org/docs/multiplatform.html)
-[![Platforms](https://img.shields.io/badge/Platforms-JVM%20%7C%20Wasm%2FJS%20%7C%20Native%20(iOS%2FiOS%20Simulator)-blue)](https://kotlinlang.org/docs/multiplatform.html)
+[![Platforms](https://img.shields.io/badge/Platforms-JVM%20%7C%20Wasm%2FJS%20%7C%20Native-blue)](https://kotlinlang.org/docs/multiplatform.html)
 [![Maven Central](https://img.shields.io/maven-central/v/io.modelcontextprotocol/kotlin-sdk.svg?label=Maven%20Central)](https://search.maven.org/search?q=g:io.modelcontextprotocol%20a:kotlin-sdk)
 [![License](https://img.shields.io/badge/License-MIT-yellow.svg)](LICENSE)
 

buildSrc/src/main/kotlin/mcp.multiplatform.gradle.kts

@@ -3,6 +3,7 @@
 import org.jetbrains.kotlin.gradle.ExperimentalWasmDsl
 import org.jetbrains.kotlin.gradle.dsl.ExplicitApiMode
 import org.jetbrains.kotlin.gradle.dsl.JvmTarget
+import org.jetbrains.kotlin.gradle.dsl.KotlinVersion.KOTLIN_2_1
 
 plugins {
     kotlin("multiplatform")
@@ -24,18 +25,40 @@ val generateLibVersion by tasks.registering {
 
             public const val LIB_VERSION: String = "${project.version}"
             
-            """.trimIndent()
+            """.trimIndent(),
         )
     }
 }
 
 kotlin {
+
+    compilerOptions {
+        languageVersion = KOTLIN_2_1
+        apiVersion = KOTLIN_2_1
+        // TODO: allWarningsAsErrors = true
+        extraWarnings = true
+        freeCompilerArgs =
+            listOf(
+                "-Xwhen-guards",
+            )
+    }
+    coreLibrariesVersion = "2.1.21"
+
     jvm {
-        compilerOptions.jvmTarget = JvmTarget.JVM_1_8
+        compilerOptions {
+            jvmTarget = JvmTarget.JVM_1_8
+            javaParameters = true
+        }
     }
-    macosX64(); macosArm64()
-    linuxX64(); linuxArm64()
+
+    macosX64()
+    macosArm64()
+
+    linuxX64()
+    linuxArm64()
+
     mingwX64()
+
     js { nodejs() }
     wasmJs { nodejs() }
 

gradle.properties

@@ -7,5 +7,9 @@ org.jetbrains.dokka.experimental.gradle.pluginMode.noWarn=true
 # Kotlin
 kotlin.code.style=official
 kotlin.daemon.jvmargs=-Xmx4G
+kotlin.native.ignoreDisabledTargets=true
 # MPP
 kotlin.mpp.enableCInteropCommonization=true
+
+# Build JS targets using npm package manager https://kotlinlang.org/docs/js-project-setup.html#npm-dependencies
+kotlin.js.yarn=false

gradle/libs.versions.toml

@@ -1,21 +1,22 @@
 [versions]
 # plugins version
-kotlin = "2.2.0"
+kotlin = "2.1.21"
 dokka = "2.0.0"
-atomicfu = "0.29.0"
+atomicfu = "0.28.0"
 ktlint = "13.0.0"
 
 # libraries version
-serialization = "1.9.0"
+binaryCompatibilityValidatorPlugin = "0.18.1"
 collections-immutable = "0.4.0"
 coroutines = "1.10.2"
-kotlinx-io = "0.8.0"
+jreleaser = "1.19.0"
+kotest = "5.9.1"
+kotlinx-datetime = "0.6.2"
+kotlinx-io = "0.7.0"
 ktor = "3.2.3"
 logging = "7.0.7"
-jreleaser = "1.19.0"
-binaryCompatibilityValidatorPlugin = "0.18.1"
+serialization = "1.8.1"
 slf4j = "2.0.17"
-kotest = "5.9.1"
 
 # Samples
 mcp-kotlin = "0.6.0"
@@ -31,11 +32,13 @@ dokka-gradle = { module = "org.jetbrains.dokka:dokka-gradle-plugin", version.ref
 jreleaser-gradle = { module = "org.jreleaser:jreleaser-gradle-plugin", version.ref = "jreleaser" }
 
 # Kotlinx libraries
-kotlinx-serialization-json = { group = "org.jetbrains.kotlinx", name = "kotlinx-serialization-json", version.ref = "serialization" }
+kotlin-logging = { group = "io.github.oshai", name = "kotlin-logging", version.ref = "logging" }
+kotlinx-collections-immutable = { group = "org.jetbrains.kotlinx", name = "kotlinx-collections-immutable", version.ref = "collections-immutable" }
 kotlinx-coroutines-core = { group = "org.jetbrains.kotlinx", name = "kotlinx-coroutines-core", version.ref = "coroutines" }
+kotlinx-datetime = { module = "org.jetbrains.kotlinx:kotlinx-datetime", version.ref = "kotlinx-datetime" }
 kotlinx-io-core = { group = "org.jetbrains.kotlinx", name = "kotlinx-io-core", version.ref = "kotlinx-io" }
-kotlinx-collections-immutable = { group = "org.jetbrains.kotlinx", name = "kotlinx-collections-immutable", version.ref = "collections-immutable" }
-kotlin-logging = { group = "io.github.oshai", name = "kotlin-logging", version.ref = "logging" }
+kotlinx-serialization-json = { group = "org.jetbrains.kotlinx", name = "kotlinx-serialization-json", version.ref = "serialization" }
+
 
 # Ktor
 ktor-client-cio = { group = "io.ktor", name = "ktor-client-cio", version.ref = "ktor" }