Apply improvements from CoreJvm Compiler

buildSrc/src/main/kotlin/io/spine/dependency/local/Compiler.kt

@@ -27,11 +27,6 @@
 package io.spine.dependency.local
 
 import io.spine.dependency.Dependency
-import io.spine.dependency.local.Compiler.DF_VERSION_ENV
-import io.spine.dependency.local.Compiler.VERSION_ENV
-import io.spine.dependency.local.Compiler.dogfoodingVersion
-import io.spine.dependency.local.Compiler.pluginLib
-import io.spine.dependency.local.Compiler.version
 
 /**
  * Dependencies on the Spine Compiler modules.

buildSrc/src/main/kotlin/io/spine/dependency/local/CoreJvmCompiler.kt

@@ -61,33 +61,20 @@ object CoreJvmCompiler {
     /**
      * The library with the [dogfoodingVersion].
      */
-    val pluginLib = pluginLibNew(dogfoodingVersion)
+    val pluginLib = pluginLib(dogfoodingVersion)
 
     /**
-     * The library with the given [version].
-     *
-     * This is the notation before the version `2.0.0-SNAPSHOT.013`
+     * The name of the published fat JAR artifact.
      */
-    @Deprecated("Use `pluginLibNew()` instead.")
-    fun pluginLib(version: String): String = "$group:core-jvm-plugins:$version:all"
+    const val fatJarArtifact = "core-jvm-plugins"
 
     /**
      * The library with the given [version].
-     *
-     * @since 2.0.0-SNAPSHOT.013
-     */
-    fun pluginLibNew(version: String): String = "$group:core-jvm-plugins:$version"
-
-    /** The artifact reference for forcing in configurations. */
-    const val pluginsArtifact: String = "$group:core-jvm-plugins:$version"
-
-    /**
-     * The `core-jvm-base` artifact with the [version].
      */
-    val base = base(version)
+    fun pluginLib(version: String): String = "$group:core-jvm-plugins:$version"
 
     /**
-     * The `core-jvm-base` artifact with the given [version].
+     * The artifact reference for forcing in configurations.
      */
-    fun base(version: String): String = "$group:core-jvm-base:$version"
+    val pluginsArtifact: String = pluginLib(version)
 }

buildSrc/src/main/kotlin/io/spine/dependency/local/TestLib.kt

@@ -33,7 +33,7 @@ package io.spine.dependency.local
  */
 @Suppress("ConstPropertyName")
 object TestLib {
-    const val version = "2.0.0-SNAPSHOT.212"
+    const val version = "2.0.0-SNAPSHOT.213"
     const val group = Spine.toolsGroup
     const val artifact = "base-testlib"
     const val lib = "$group:$artifact:$version"

buildSrc/src/main/kotlin/io/spine/gradle/publish/SpinePublishing.kt

@@ -149,10 +149,8 @@ import org.gradle.kotlin.dsl.findByType
  */
 fun Project.spinePublishing(block: SpinePublishing.() -> Unit): SpinePublishing {
     apply<MavenPublishPlugin>()
-    val name = SpinePublishing::class.java.simpleName
-        .replaceFirstChar { it.lowercase(Locale.getDefault()) }
     val extension = with(extensions) {
-        findByType<SpinePublishing>() ?: create(name, project)
+        findByType<SpinePublishing>() ?: create(SpinePublishing.extensionName, project)
     }
     extension.run {
         block()
@@ -192,6 +190,12 @@ open class SpinePublishing(private val project: Project) {
          * to a tool module's artifact ID.
          */
         const val NONE_PREFIX = "NONE"
+
+        /**
+         * The name of the extension registered in a Gradle project.
+         */
+        public val extensionName: String = SpinePublishing::class.java.simpleName
+            .replaceFirstChar { it.lowercase(Locale.ROOT) }
     }
 
     private val testJar = TestJar()
@@ -346,13 +350,14 @@ open class SpinePublishing(private val project: Project) {
      *
      * @see modules
      */
-    private fun projectsToPublish(): Collection<Project> {
+    fun projectsToPublish(): Set<Project> {
         if (project.subprojects.isEmpty()) {
             return setOf(project)
         }
         return modules.union(modulesWithCustomPublishing)
             .map { name -> project.project(name) }
             .ifEmpty { setOf(project) }
+            .toSet()
     }
 
     /**

buildSrc/src/test/kotlin/io/spine/gradle/publish/SpinePublishingTest.kt

@@ -156,10 +156,9 @@ class SpinePublishingTest {
             // Let's use it instead of creating a second one with a different name.
             extension.modules = setOf("sub")
 
-            // Subproject's extension must be named 'SpinePublishing' 
-            // to be found by SpinePublishing::class.java.simpleName
-            val extensionName = SpinePublishing::class.java.simpleName
-            val subExtension = subproject.extensions.create<SpinePublishing>(extensionName, subproject)
+            val extensionName = SpinePublishing.extensionName
+            val subExtension =
+                subproject.extensions.create<SpinePublishing>(extensionName, subproject)
 
             val exception = shouldThrow<IllegalStateException> {
                 subExtension.configured()