Update Kotlin to 1.7.10 and turn on compatibility mode till Kotlin 1.4

This requires kotest to be updated to 5.4.0.
Add maven central version badge.

Author: nsk90

README.md

@@ -3,6 +3,7 @@
 ![Build and test with Gradle](https://github.com/nsk90/kstatemachine/workflows/Build%20and%20test%20with%20Gradle/badge.svg)
 [![Quality Gate Status](https://sonarcloud.io/api/project_badges/measure?project=nsk90_kstatemachine&metric=alert_status)](https://sonarcloud.io/dashboard?id=nsk90_kstatemachine)
 [![](https://jitpack.io/v/nsk90/kstatemachine.svg)](https://jitpack.io/#nsk90/kstatemachine)
+![Maven Central](https://img.shields.io/maven-central/v/io.github.nsk90/kstatemachine)
 ![Dependencies none](https://img.shields.io/badge/dependencies-none-green)
 [![codecov](https://codecov.io/gh/nsk90/kstatemachine/branch/master/graph/badge.svg?token=IR2JR43FOZ)](https://codecov.io/gh/nsk90/kstatemachine)
 [![Android Arsenal]( https://img.shields.io/badge/Android%20Arsenal-KStateMachine-green.svg?style=flat )]( https://android-arsenal.com/details/1/8276 )
@@ -17,6 +18,7 @@ Main features are:
 
 * Zero dependency. It is written in pure Kotlin, it does not depend on any other libraries or Android SDK
 * Kotlin DSL syntax for defining state machine structure. Using without DSL is also possible
+* Backward compatible till Kotlin 1.4
 * Event based - transitions are performed by processing incoming events
 * Listeners for machine, states and transitions, all callbacks are shipped with information about current transition
 * [Guarded](https://github.com/nsk90/kstatemachine/wiki#guarded-transitions)

buildSrc/build.gradle.kts

@@ -1,5 +1,3 @@
-import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
-
 plugins {
     `kotlin-dsl`
 }
@@ -8,10 +6,6 @@ repositories {
     mavenCentral()
 }
 
-tasks.withType<KotlinCompile> {
-    kotlinOptions.jvmTarget = "1.8"
-}
-
 java {
     sourceCompatibility = JavaVersion.VERSION_1_8
     targetCompatibility = JavaVersion.VERSION_1_8

buildSrc/src/main/kotlin/ru/nsk/Versions.kt

@@ -1,9 +1,15 @@
 object Versions {
-    const val kotlin = "1.6.10"
+    // tools
+    const val kotlin = "1.7.10"
     const val gradle = "7.1.0"
 
+    // compatibility
+    const val jvmTarget = "1.8"
+    const val languageVersion = "1.4"
+    const val apiVersion = "1.4"
+
     // dependencies
-    const val mockk = "1.12.2"
-    const val kotestAssertions = "5.1.0"
-    const val kotestRunner = "5.1.0"
+    const val mockk = "1.12.5"
+    const val kotestAssertions = "5.4.0"
+    const val kotestRunner = "5.4.0"
 }

kstatemachine/build.gradle.kts

@@ -13,6 +13,16 @@ tasks.test {
     useJUnitPlatform()
 }
 
+tasks {
+    compileKotlin {
+        kotlinOptions {
+            jvmTarget = Versions.jvmTarget
+            languageVersion = Versions.languageVersion
+            apiVersion = Versions.apiVersion
+        }
+    }
+}
+
 dependencies {
     testImplementation("io.kotest:kotest-assertions-core:${Versions.kotestAssertions}")
     testImplementation("io.kotest:kotest-runner-junit5:${Versions.kotestRunner}")

kstatemachine/src/main/kotlin/ru/nsk/kstatemachine/Utils.kt

@@ -0,0 +1,11 @@
+package ru.nsk.kstatemachine
+
+internal inline fun <T, R : Any> Iterable<T>.firstNotNullOfOrNull(transform: (T) -> R?): R? {
+    for (element in this) {
+        val result = transform(element)
+        if (result != null) {
+            return result
+        }
+    }
+    return null
+}