Rename root MPP module and publish the JVM JAR within

* Rename the JVM module: empty suffix -> '-jvm';
* Rename the root MPP module: '-native' -> empty suffix;
* Publish the JVM JAR and POM in the root MPP module, so
  that consumers who can't read Gradle module metadata, such
  as Maven or old Gradle versions, get the JVM resolution
  result from the root MPP module.

Author: h0tk3y

gradle/publish-bintray.gradle

@@ -64,22 +64,24 @@ publishing {
     publications.all {
         MavenCentralKt.configureMavenCentralMetadata(pom, project)
 
-        // add empty javadocs (no need for MPP root publication which publishes only pom file)
-        if (it.name != 'kotlinMultiplatform' && !isBom) {
+        // add empty javadocs
+        if (!isBom && it.name != "kotlinMultiplatform") {
             it.artifact(javadocJar)
         }
 
         // Rename MPP artifacts for backward compatibility
         def type = it.name
         switch (type) {
             case 'kotlinMultiplatform':
-                it.artifactId = "$project.name-native"
+                it.artifactId = "$project.name"
+                apply from: "$rootDir/gradle/publish-mpp-root-module-in-platform.gradle"
+                publishPlatformArtifactsInRootModule(publications["jvm"])
                 break
             case 'metadata':
                 it.artifactId = "$project.name-common"
                 break
             case 'jvm':
-                it.artifactId = "$project.name"
+                it.artifactId = "$project.name-jvm"
                 break
             case 'js':
             case 'native':

gradle/publish-mpp-root-module-in-platform.gradle

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2014-2020 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
+ */
+
+
+/** Publish the platform JAR and POM so that consumers who depend on this module and can't read Gradle module
+   metadata can still get the platform artifact and transitive dependencies from the POM: */
+project.ext.publishPlatformArtifactsInRootModule = { platformPublication ->
+    def platformPomBuilder = null
+
+    platformPublication.pom.withXml { platformPomBuilder = asString() }
+
+    publishing.publications.kotlinMultiplatform {
+        platformPublication.artifacts.forEach {
+            artifact(it)
+        }
+
+        pom.withXml {
+            def pomStringBuilder = asString()
+            pomStringBuilder.setLength(0)
+            // The platform POM needs its artifact ID replaced with the artifact ID of the root module:
+            def platformPomString = platformPomBuilder.toString()
+            platformPomString.eachLine { line ->
+                if (!line.contains("<!--")) { // Remove the Gradle module metadata marker as it will be added anew
+                    pomStringBuilder.append(line.replace(platformPublication.artifactId, artifactId))
+                    pomStringBuilder.append("\n")
+                }
+            }
+        }
+    }
+
+    tasks.matching { it.name == "generatePomFileForKotlinMultiplatformPublication"}.configureEach {
+        dependsOn(tasks["generatePomFileFor${platformPublication.name.capitalize()}Publication"])
+    }
+}