Move Kotlin Gradle build config to convention

This commit moves the Kotlin build configuration from the Gradle DSL
to a dedicated convention in buildSrc.

Author: bclozel

build.gradle

@@ -1,8 +1,8 @@
 plugins {
 	id 'io.spring.nohttp' version '0.0.10'
 	id 'io.freefair.aspectj' version '6.5.0.3' apply false
-	id 'org.jetbrains.kotlin.jvm' version '1.7.20' apply false
-	id 'org.jetbrains.kotlin.plugin.serialization' version '1.7.20' apply false
+	// kotlinVersion is managed in gradle.properties
+	id 'org.jetbrains.kotlin.plugin.serialization' version "${kotlinVersion}" apply false
 	id 'org.jetbrains.dokka' version '1.7.20'
 	id 'org.asciidoctor.jvm.convert' version '3.3.2' apply false
 	id 'org.asciidoctor.jvm.pdf' version '3.3.2'  apply false
@@ -16,9 +16,6 @@ plugins {
 ext {
 	moduleProjects = subprojects.findAll { it.name.startsWith("spring-") }
 	javaProjects = subprojects - project(":framework-bom") - project(":framework-platform")
-	withoutJclOverSlf4j = {
-		exclude group: "org.slf4j", name: "jcl-over-slf4j"
-	}
 }
 
 configure(allprojects) { project ->
@@ -59,23 +56,6 @@ configure([rootProject] + javaProjects) { project ->
 		matching { it.name.endsWith("Classpath") }.all { it.extendsFrom(dependencyManagement) }
 	}
 
-	pluginManager.withPlugin("kotlin") {
-
-		compileKotlin {
-			kotlinOptions {
-				languageVersion = "1.7"
-				apiVersion = "1.7"
-				freeCompilerArgs = ["-Xjsr305=strict", "-Xsuppress-version-warnings", "-opt-in=kotlin.RequiresOptIn"]
-				allWarningsAsErrors = true
-			}
-		}
-		compileTestKotlin {
-			kotlinOptions {
-				freeCompilerArgs = ["-Xjsr305=strict", "-opt-in=kotlin.RequiresOptIn"]
-			}
-		}
-	}
-
 	test {
 		useJUnitPlatform()
 		include(["**/*Tests.class", "**/*Test.class"])
@@ -165,7 +145,6 @@ configure(moduleProjects) { project ->
 configure(rootProject) {
 	description = "Spring Framework"
 
-	apply plugin: "kotlin"
 	apply plugin: "io.spring.nohttp"
 	apply plugin: 'org.springframework.build.api-diff'
 
@@ -188,4 +167,4 @@ configure(rootProject) {
 		maxHeapSize = "1g"
 	}
 
-}
+}                                         

buildSrc/README.md

@@ -7,7 +7,8 @@ They are declared in the `build.gradle` file in this folder.
 
 The `org.springframework.build.conventions` plugin applies all conventions to the Framework build:
 
-* Configuring the Java compiler, see `CompilerConventions`
+* Configuring the Java compiler, see `JavaConventions`
+* Configuring the Kotlin compiler, see `KotlinConventions`
 * Configuring testing in the build with `TestConventions` 
 
 

buildSrc/build.gradle

@@ -7,7 +7,18 @@ repositories {
 	gradlePluginPortal()
 }
 
+ext {
+	def propertiesFile = new File(new File("$projectDir").parentFile, "gradle.properties")
+	propertiesFile.withInputStream {
+		def properties = new Properties()
+		properties.load(it)
+		set("kotlinVersion", properties["kotlinVersion"])
+	}
+}
+
 dependencies {
+	implementation("org.jetbrains.kotlin:kotlin-gradle-plugin:${kotlinVersion}")
+	implementation("org.jetbrains.kotlin:kotlin-compiler-embeddable:${kotlinVersion}")
 	implementation "me.champeau.gradle:japicmp-gradle-plugin:0.3.0"
 	implementation "org.gradle:test-retry-gradle-plugin:1.4.1"
 }

buildSrc/src/main/java/org/springframework/build/ConventionsPlugin.java

@@ -19,14 +19,17 @@
 import org.gradle.api.Plugin;
 import org.gradle.api.Project;
 import org.gradle.api.plugins.JavaBasePlugin;
+import org.jetbrains.kotlin.gradle.plugin.KotlinBasePlugin;
 
 /**
  * Plugin to apply conventions to projects that are part of Spring Framework's build.
  * Conventions are applied in response to various plugins being applied.
  *
  * When the {@link JavaBasePlugin} is applied, the conventions in {@link TestConventions}
  * are applied.
- * When the {@link JavaBasePlugin} is applied, the conventions in {@link CompilerConventions}
+ * When the {@link JavaBasePlugin} is applied, the conventions in {@link JavaConventions}
+ * are applied.
+ * When the {@link KotlinBasePlugin} is applied, the conventions in {@link KotlinConventions}
  * are applied.
  *
  * @author Brian Clozel
@@ -35,7 +38,8 @@ public class ConventionsPlugin implements Plugin<Project> {
 
 	@Override
 	public void apply(Project project) {
+		new JavaConventions().apply(project);
+		new KotlinConventions().apply(project);
 		new TestConventions().apply(project);
-		new CompilerConventions().apply(project);
 	}
 }

buildSrc/src/main/java/org/springframework/build/CompilerConventions.java renamed to buildSrc/src/main/java/org/springframework/build/JavaConventions.java

@@ -33,7 +33,7 @@
  * @author Sam Brannen
  * @author Sebastien Deleuze
  */
-public class CompilerConventions {
+public class JavaConventions {
 
 	private static final List<String> COMPILER_ARGS;
 

buildSrc/src/main/java/org/springframework/build/KotlinConventions.java

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2002-2022 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.build;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.gradle.api.Project;
+import org.jetbrains.kotlin.gradle.dsl.KotlinJvmOptions;
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile;
+
+/**
+ * @author Brian Clozel
+ */
+public class KotlinConventions {
+
+	void apply(Project project) {
+		project.getPlugins().withId("org.jetbrains.kotlin.jvm",
+				(plugin) -> project.getTasks().withType(KotlinCompile.class, this::configure));
+	}
+
+	private void configure(KotlinCompile compile) {
+		KotlinJvmOptions kotlinOptions = compile.getKotlinOptions();
+		kotlinOptions.setApiVersion("1.7");
+		kotlinOptions.setLanguageVersion("1.7");
+		kotlinOptions.setJvmTarget("17");
+		kotlinOptions.setAllWarningsAsErrors(true);
+		List<String> freeCompilerArgs = new ArrayList<>(compile.getKotlinOptions().getFreeCompilerArgs());
+		freeCompilerArgs.addAll(List.of("-Xsuppress-version-warnings", "-Xjsr305=strict", "-opt-in=kotlin.RequiresOptIn"));
+		compile.getKotlinOptions().setFreeCompilerArgs(freeCompilerArgs);
+	}
+
+}

gradle.properties

@@ -1,5 +1,9 @@
 version=6.0.0-SNAPSHOT
-org.gradle.jvmargs=-Xmx2048m
+
 org.gradle.caching=true
+org.gradle.jvmargs=-Xmx2048m
 org.gradle.parallel=true
+
+kotlinVersion=1.7.20
+
 kotlin.stdlib.default.dependency=false