Remove Kotlin extensions (reactor#2949)

This commit removes Kotlin extensions from core repo, since they have
been replaced with those in reactor-kotlin-extensions repository.

This also removes dependencies to Kotlin stdlib, language, plugins...
as well as kotlin entries in the generated OSGI manifests.

Finally, a japicmp exception is added for the removed classes.

Fixes reactor#2912.

.github/renovate.json

@@ -61,11 +61,6 @@
       "groupName": "Micrometer 1.3.0",
       "groupSlug": "micrometer",
       "allowedVersions": "=1.3.0"
-    },
-    {
-      "matchPackagePrefixes": ["org.jetbrains.kotlin"],
-      "groupName": "Kotlin",
-      "allowedVersions": "<1.6.0"
     }
   ]
 }

build.gradle

@@ -26,7 +26,6 @@ buildscript {
 
 
 plugins {
-	alias(libs.plugins.kotlin)
 	alias(libs.plugins.artifactory)
 	alias(libs.plugins.shadow)
 	alias(libs.plugins.asciidoctor.convert) apply false
@@ -215,27 +214,4 @@ configure(subprojects) { p ->
 	// these apply once the above configure is done, but before project-specific build.gradle have applied
 	apply plugin: "io.reactor.gradle.java-conventions"
 	apply from: "${rootDir}/gradle/javadoc.gradle"
-
-	// these apply AFTER project-specific build.gradle have applied
-	afterEvaluate {
-		if (p.plugins.hasPlugin("kotlin")) {
-			println "Applying Kotlin conventions to ${p.name}"
-			compileKotlin {
-				kotlinOptions {
-					jvmTarget = "1.8"
-					freeCompilerArgs = ["-Xjsr305=strict"]
-					languageVersion = "1.3" //TODO kotlin languageVersion 1.3 is now deprecated
-					apiVersion = "1.3"
-				}
-			}
-			compileTestKotlin {
-				kotlinOptions {
-					jvmTarget = "1.8"
-					freeCompilerArgs = ["-Xjsr305=strict"]
-					languageVersion = "1.3" //TODO kotlin languageVersion 1.3 is now deprecated
-					apiVersion = "1.3"
-				}
-			}
-		}
-	}
 }

gradle/libs.versions.toml

@@ -9,7 +9,6 @@ asciidoctor = "3.3.2"
 bytebuddy = "1.12.8"
 jmh = "1.34"
 junit = "5.8.2"
-kotlin = "1.5.32"
 reactiveStreams = "1.0.3"
 
 [libraries]
@@ -26,7 +25,6 @@ jmh-core = { module = "org.openjdk.jmh:jmh-core", version.ref = "jmh" }
 jsr166backport = "io.projectreactor:jsr166:1.0.0.RELEASE"
 jsr305 = "com.google.code.findbugs:jsr305:3.0.1"
 junit-bom = { module = "org.junit:junit-bom", version.ref = "junit" }
-kotlin-stdlib = { module = "org.jetbrains.kotlin:kotlin-stdlib", version.ref = "kotlin" }
 logback = "ch.qos.logback:logback-classic:1.2.11"
 micrometer = "io.micrometer:micrometer-core:1.3.0"
 mockito = "org.mockito:mockito-core:4.3.1"
@@ -46,7 +44,6 @@ bnd = { id = "biz.aQute.bnd.builder", version = "6.2.0" }
 download = { id = "de.undercouch.download", version = "5.0.1" }
 japicmp = { id = "me.champeau.gradle.japicmp", version = "0.3.1" }
 jcstress = { id = "io.github.reyerizo.gradle.jcstress", version = "0.8.13" }
-kotlin = { id = "org.jetbrains.kotlin.jvm", version.ref = "kotlin" }
 nohttp = { id = "io.spring.nohttp", version = "0.0.10" }
 shadow = { id = "com.github.johnrengelman.shadow", version = "7.1.2" }
 spotless = { id = "com.diffplug.spotless", version = "6.3.0" }

reactor-core/build.gradle

@@ -19,8 +19,8 @@ import me.champeau.gradle.japicmp.JapicmpTask
 apply plugin: 'idea' // needed to avoid IDEA seeing the jmh folder as source
 apply plugin: 'biz.aQute.bnd.builder'
 apply plugin: 'org.unbroken-dome.test-sets'
-apply plugin: 'kotlin'
 apply plugin: 'jcstress'
+apply plugin: 'java-library'
 
 ext {
 	bndOptions = [
@@ -33,7 +33,6 @@ ext {
 			"!javax.annotation",
 			"!javax.annotation.meta",
 			'org.slf4j;resolution:=optional;version="[1.5.4,2)"',
-			"kotlin.*;resolution:=optional",
 			"reactor.blockhound.*;resolution:=optional",
 			"io.micrometer.*;resolution:=optional",
 			"*"
@@ -86,10 +85,6 @@ dependencies {
 	// Optional Metrics
 	compileOnly libs.micrometer
 
-	// Not putting kotlin-stdlib as implementation to not force it as a transitive lib
-	compileOnly libs.kotlin.stdlib
-	testImplementation libs.kotlin.stdlib
-
 	// Optional BlockHound support
 	compileOnly libs.blockhound
 	// Also make BlockHound visible in the CP of dedicated testset
@@ -161,7 +156,12 @@ task japicmp(type: JapicmpTask) {
 
 	// TODO after a .0 release, bump the gradle.properties baseline
 	// TODO after a .0 release, remove the reactor-core exclusions below if any
-	classExcludes = [ ]
+	classExcludes = [
+		"reactor.core.publisher.FluxExtensionsKt",
+		"reactor.core.publisher.MonoExtensionsKt",
+		"reactor.core.publisher.MonoWhenFunctionsKt",
+		"reactor.util.function.TupleExtensionsKt"
+	]
 	methodExcludes = [ 'reactor.core.publisher.Sinks$EmitFailureHandler#busyLooping(java.time.Duration)' ]
 }