Enable forbiddenapis server java9 (#33245)

Author: alpar-t

buildSrc/src/main/groovy/org/elasticsearch/gradle/BuildPlugin.groovy

@@ -38,7 +38,6 @@ import org.gradle.api.artifacts.ModuleDependency
 import org.gradle.api.artifacts.ModuleVersionIdentifier
 import org.gradle.api.artifacts.ProjectDependency
 import org.gradle.api.artifacts.ResolvedArtifact
-import org.gradle.api.artifacts.SelfResolvingDependency
 import org.gradle.api.artifacts.dsl.RepositoryHandler
 import org.gradle.api.execution.TaskExecutionGraph
 import org.gradle.api.plugins.JavaPlugin
@@ -212,6 +211,7 @@ class BuildPlugin implements Plugin<Project> {
             project.rootProject.ext.minimumRuntimeVersion = minimumRuntimeVersion
             project.rootProject.ext.inFipsJvm = inFipsJvm
             project.rootProject.ext.gradleJavaVersion = JavaVersion.toVersion(gradleJavaVersion)
+            project.rootProject.ext.java9Home = findJavaHome("9")
         }
 
         project.targetCompatibility = project.rootProject.ext.minimumRuntimeVersion
@@ -225,6 +225,7 @@ class BuildPlugin implements Plugin<Project> {
         project.ext.javaVersions = project.rootProject.ext.javaVersions
         project.ext.inFipsJvm = project.rootProject.ext.inFipsJvm
         project.ext.gradleJavaVersion = project.rootProject.ext.gradleJavaVersion
+        project.ext.java9Home = project.rootProject.ext.java9Home
     }
 
     private static String getPaddedMajorVersion(JavaVersion compilerJavaVersionEnum) {

buildSrc/src/main/groovy/org/elasticsearch/gradle/precommit/PrecommitTasks.groovy

@@ -100,7 +100,7 @@ class PrecommitTasks {
 
     private static Task configureForbiddenApisCli(Project project) {
         Task forbiddenApisCli = project.tasks.create('forbiddenApis')
-        project.sourceSets.forEach { sourceSet ->
+        project.sourceSets.all { sourceSet ->
             forbiddenApisCli.dependsOn(
                 project.tasks.create(sourceSet.getTaskName('forbiddenApis', null), ForbiddenApisCliTask) {
                     ExportElasticsearchBuildResourcesTask buildResources = project.tasks.getByName('buildResources')

libs/core/build.gradle

@@ -46,12 +46,13 @@ if (!isEclipse && !isIdea) {
         targetCompatibility = 9
     }
 
-    /* Enable this when forbiddenapis was updated to 2.6.
-     * See: https://github.com/elastic/elasticsearch/issues/29292
     forbiddenApisJava9 {
-        targetCompatibility = 9
+        if (project.runtimeJavaVersion < JavaVersion.VERSION_1_9) {
+            targetCompatibility = JavaVersion.VERSION_1_9
+            javaHome = project.java9Home
+        }
+        replaceSignatureFiles 'jdk-signatures'
     }
-     */
 
     jar {
         metaInf {

server/build.gradle

@@ -58,13 +58,13 @@ if (!isEclipse && !isIdea) {
     sourceCompatibility = 9
     targetCompatibility = 9
   }
-  
-  /* Enable this when forbiddenapis was updated to 2.6.
-   * See: https://github.com/elastic/elasticsearch/issues/29292
+
   forbiddenApisJava9 {
-    targetCompatibility = 9
+    if (project.runtimeJavaVersion < JavaVersion.VERSION_1_9) {
+      targetCompatibility = JavaVersion.VERSION_1_9
+      javaHome = project.java9Home
+    }
   }
-  */
 
   jar {
     metaInf {