Validate mrjar plugin versions (elastic#120823) (elastic#120942) (elastic#122608)

* Validate mrjar plugin versions (elastic#120823)

The mrjar plugin adds support for sourcesets named in the form mainNN,
which adds the appropriate compiler and other settings for that version
of Java, and produces a multi-release jar. Having multi-release jars
only makes sense for versions of java newer than the minimum compile
version. This commit adds validation that the version is not too old.

Note that the check is slightly relaxed; it allows mainNN where NN is
equal to the min java version. This is due to the desire to keep
code using incubating modules separate because warnings must be
disabled.

* Restore deleted files

* restore classifier fix

---------

Co-authored-by: Elastic Machine <[email protected]>

Author: rjernst

build-tools-internal/src/main/java/org/elasticsearch/gradle/internal/MrjarPlugin.java

@@ -72,12 +72,13 @@ public void apply(Project project) {
         var javaExtension = project.getExtensions().getByType(JavaPluginExtension.class);
         var isIdeaSync = System.getProperty("idea.sync.active", "false").equals("true");
         var ideaSourceSetsEnabled = project.hasProperty(MRJAR_IDEA_ENABLED) && project.property(MRJAR_IDEA_ENABLED).equals("true");
+        int minJavaVersion = Integer.parseInt(buildParams.getMinimumCompilerVersion().getMajorVersion());
 
         // Ignore version-specific source sets if we are importing into IntelliJ and have not explicitly enabled this.
         // Avoids an IntelliJ bug:
         // https://youtrack.jetbrains.com/issue/IDEA-285640/Compiler-Options-Settings-language-level-is-set-incorrectly-with-JDK-19ea
         if (isIdeaSync == false || ideaSourceSetsEnabled) {
-            List<Integer> mainVersions = findSourceVersions(project);
+            List<Integer> mainVersions = findSourceVersions(project, minJavaVersion);
             List<String> mainSourceSets = new ArrayList<>();
             mainSourceSets.add(SourceSet.MAIN_SOURCE_SET_NAME);
             List<String> testSourceSets = new ArrayList<>(mainSourceSets);
@@ -101,6 +102,7 @@ public void apply(Project project) {
     }
 
     private void configureMrjar(Project project) {
+
         var jarTask = project.getTasks().withType(Jar.class).named(JavaPlugin.JAR_TASK_NAME);
         jarTask.configure(task -> { task.manifest(manifest -> { manifest.attributes(Map.of("Multi-Release", "true")); }); });
 
@@ -216,7 +218,7 @@ private void createTestTask(
         project.getTasks().named("check").configure(checkTask -> checkTask.dependsOn(testTaskProvider));
     }
 
-    private static List<Integer> findSourceVersions(Project project) {
+    private static List<Integer> findSourceVersions(Project project, int minJavaVersion) {
         var srcDir = project.getProjectDir().toPath().resolve("src");
         List<Integer> versions = new ArrayList<>();
         try (var subdirStream = Files.list(srcDir)) {
@@ -225,7 +227,23 @@ private static List<Integer> findSourceVersions(Project project) {
                 String sourcesetName = sourceSetPath.getFileName().toString();
                 Matcher sourcesetMatcher = MRJAR_SOURCESET_PATTERN.matcher(sourcesetName);
                 if (sourcesetMatcher.matches()) {
-                    versions.add(Integer.parseInt(sourcesetMatcher.group(1)));
+                    int version = Integer.parseInt(sourcesetMatcher.group(1));
+                    if (version < minJavaVersion) {
+                        // NOTE: We allow mainNN for the min java version so that incubating modules can be used without warnings.
+                        // It is a workaround for https://bugs.openjdk.org/browse/JDK-8187591. Once min java is 22, we
+                        // can use the SuppressWarnings("preview") in the code using incubating modules and this check
+                        // can change to <=
+                        throw new IllegalArgumentException(
+                            "Found src dir '"
+                                + sourcesetName
+                                + "' for Java "
+                                + version
+                                + " but multi-release jar sourceset should have version "
+                                + minJavaVersion
+                                + " or greater"
+                        );
+                    }
+                    versions.add(version);
                 }
             }
         } catch (IOException e) {