Add project JDK convention (Kotlin#1984)

Author: turansky

build.gradle

@@ -3,6 +3,7 @@
  */
 import org.jetbrains.kotlin.konan.target.HostManager
 
+apply plugin: 'jdk-convention'
 apply from: rootProject.file("gradle/experimental.gradle")
 
 def rootModule = "kotlinx.coroutines"
@@ -69,7 +70,6 @@ buildscript {
         classpath "org.jetbrains.kotlinx:atomicfu-gradle-plugin:$atomicfu_version"
         classpath "org.jetbrains.kotlinx:kotlinx-knit:$knit_version"
         classpath "com.moowork.gradle:gradle-node-plugin:$gradle_node_version"
-        classpath "org.openjfx:javafx-plugin:$javafx_plugin_version"
         classpath "org.jetbrains.kotlinx:binary-compatibility-validator:$binary_compatibility_validator_version"
 
         // JMH plugins
@@ -264,22 +264,9 @@ configure(subprojects.findAll { !unpublished.contains(it.name) }) {
 // Report Kotlin compiler version when building project
 println("Using Kotlin compiler version: $org.jetbrains.kotlin.config.KotlinCompilerVersion.VERSION")
 
-// --------------- Publish only from under JDK11+ ---------------
-task checkJdkForPublish {
-    doFirst {
-        if (JavaVersionKt.javaVersionMajor < 11) {
-            throw new GradleException("Project can be build for publishing only under JDK 11+, but found ${JavaVersionKt.javaVersion}")
-        }
-    }
-}
-
 // --------------- Configure sub-projects that are published ---------------
 def publishTasks = getTasksByName("publish", true) + getTasksByName("publishNpm", true)
 
-publishTasks.each {
-    it.dependsOn checkJdkForPublish
-}
-
 task deploy(dependsOn: publishTasks)
 
 apply plugin: 'base'

buildSrc/src/main/kotlin/Idea.kt

@@ -0,0 +1,4 @@
+object Idea {
+    val active: Boolean
+        get() = System.getProperty("idea.active") == "true"
+}

buildSrc/src/main/kotlin/JavaVersion.kt

@@ -0,0 +1,10 @@
+import org.gradle.api.JavaVersion
+
+if (!JavaVersion.current().isJava11Compatible) {
+    val message = "Project required JDK 11+, but found ${JavaVersion.current()}"
+    if (Idea.active) {
+        logger.error(message)
+    } else {
+        throw GradleException(message)
+    }
+}

buildSrc/src/main/kotlin/jdk-convention.gradle.kts

@@ -4,6 +4,9 @@
 
 pluginManagement {
     plugins {
+        id "org.openjfx.javafxplugin" version javafx_plugin_version
+
+        // JMH
         id "net.ltgt.apt" version "0.21"
         id "me.champeau.gradle.jmh" version "0.5.0-rc-2"
     }

settings.gradle

@@ -2,15 +2,14 @@
  * Copyright 2016-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
  */
 
-// JDK11+ does not bundle JavaFx and the plugin for JavaFx support is compiled with class file version 55.0 (JDK 11)
-if (JavaVersionKt.javaVersionMajor >= 11) {
-    apply plugin: 'org.openjfx.javafxplugin'
+plugins {
+  id 'org.openjfx.javafxplugin'
+}
 
-    javafx {
-        version = javafx_version
-        modules = ['javafx.controls']
-        configuration = 'compile'
-    }
+javafx {
+    version = javafx_version
+    modules = ['javafx.controls']
+    configuration = 'compile'
 }
 
 task checkJdk8() {