refactor the LG check into its own task, minor rewrite for kotlin convention

Author: David Motsonashvili

buildSrc/src/main/java/com/google/firebase/gradle/plugins/PublishingPlugin.kt

@@ -81,6 +81,8 @@ abstract class PublishingPlugin : Plugin<Project> {
         registerCheckHeadDependenciesTask(project, releasingFirebaseLibraries)
       val validateProjectsToPublish =
         registerValidateProjectsToPublishTask(project, releasingFirebaseLibraries)
+      val validateLibraryGroupsToPublish =
+        registerValidateLibraryGroupsToPublishTask(project, releasingFirebaseLibraries)
       val publishReleasingLibrariesToBuildDir =
         registerPublishReleasingLibrariesToBuildDirTask(project, releasingProjects)
       val generateKotlindocsForRelease =
@@ -128,6 +130,7 @@ abstract class PublishingPlugin : Plugin<Project> {
       project.tasks.register(FIREBASE_PUBLISH_TASK) {
         dependsOn(
           validateProjectsToPublish,
+          validateLibraryGroupsToPublish,
           checkHeadDependencies,
           // validatePomForRelease, TODO(b/279466888) - Make GmavenHelper testable
           buildMavenZip,
@@ -299,6 +302,29 @@ abstract class PublishingPlugin : Plugin<Project> {
       }
     }
 
+  /**
+   * Registers the [VALIDATE_LIBRARY_GROUPS_TO_PUBLISH_TASK] task.
+   *
+   * Validates that all library groups of all publishing projects are included in the release config
+   *
+   * @throws GradleException if a library is releasing without it's library group.
+   */
+  private fun registerValidateLibraryGroupsToPublishTask(
+    project: Project,
+    releasinglibraries: List<FirebaseLibraryExtension>
+  ) =
+    project.tasks.register(VALIDATE_LIBRARY_GROUPS_TO_PUBLISH_TASK) {
+      doLast {
+        val libraryGroupProjects = releasinglibraries.flatMap { it.librariesToRelease }
+        val missingProjects = libraryGroupProjects - releasinglibraries
+        if (missingProjects.isNotEmpty()) {
+          throw GradleException(
+            "Some libraries in library groups are not in the release: ${missingProjects.map { it.mavenName }}"
+          )
+        }
+      }
+    }
+
   /**
    * Registers the [PUBLISH_RELEASING_LIBS_TO_BUILD_TASK] task.
    *
@@ -475,6 +501,7 @@ abstract class PublishingPlugin : Plugin<Project> {
 
     const val GENERATE_BOM_TASK = "generateBom"
     const val VALIDATE_PROJECTS_TO_PUBLISH_TASK = "validateProjectsToPublish"
+    const val VALIDATE_LIBRARY_GROUPS_TO_PUBLISH_TASK = "validateLGsToPublish"
     const val SEMVER_CHECK_TASK = "semverCheckForRelease"
     const val RELEASE_GENEATOR_TASK = "generateReleaseConfig"
     const val VALIDATE_POM_TASK = "validatePomForRelease"