[Backport] [2.x] Allow @InternalApi annotation on classes not meant to be constructed outside of the OpenSearch core (#14575)

CHANGELOG.md

@@ -29,6 +29,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - unsignedLongRangeQuery now returns MatchNoDocsQuery if the lower bounds are greater than the upper bounds ([#14416](https://github.com/opensearch-project/OpenSearch/pull/14416))
 - Make the class CommunityIdProcessor final ([#14448](https://github.com/opensearch-project/OpenSearch/pull/14448))
 - Updated the `indices.query.bool.max_clause_count` setting from being static to dynamically updateable ([#13568](https://github.com/opensearch-project/OpenSearch/pull/13568))
+- Allow @InternalApi annotation on classes not meant to be constructed outside of the OpenSearch core ([#14575](https://github.com/opensearch-project/OpenSearch/pull/14575))
 
 ### Deprecated
 

libs/common/src/test/java/org/opensearch/common/annotation/processor/ApiAnnotationProcessorTests.java

@@ -473,4 +473,17 @@ public void testPublicApiWithProtectedInterface() {
 
         assertThat(failure.diagnotics(), not(hasItem(matching(Diagnostic.Kind.ERROR))));
     }
+
+    /**
+     * The constructor arguments have relaxed semantics at the moment: those could be not annotated or be annotated as {@link InternalApi}
+     */
+    public void testPublicApiConstructorAnnotatedInternalApi() {
+        final CompilerResult result = compile("PublicApiConstructorAnnotatedInternalApi.java", "NotAnnotated.java");
+        assertThat(result, instanceOf(Failure.class));
+
+        final Failure failure = (Failure) result;
+        assertThat(failure.diagnotics(), hasSize(2));
+
+        assertThat(failure.diagnotics(), not(hasItem(matching(Diagnostic.Kind.ERROR))));
+    }
 }

libs/common/src/test/resources/org/opensearch/common/annotation/processor/InternalApiAnnotated.java

@@ -8,9 +8,9 @@
 
 package org.opensearch.common.annotation.processor;
 
-import org.opensearch.common.annotation.PublicApi;
+import org.opensearch.common.annotation.InternalApi;
 
-@PublicApi(since = "1.0.0")
+@InternalApi
 public class InternalApiAnnotated {
 
 }

libs/common/src/test/resources/org/opensearch/common/annotation/processor/PublicApiConstructorAnnotatedInternalApi.java

@@ -0,0 +1,21 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.common.annotation.processor;
+
+import org.opensearch.common.annotation.InternalApi;
+import org.opensearch.common.annotation.PublicApi;
+
+@PublicApi(since = "1.0.0")
+public class PublicApiConstructorAnnotatedInternalApi {
+    /**
+     * The constructors have relaxed semantics at the moment: those could be not annotated or be annotated as {@link InternalApi}
+     */
+    @InternalApi
+    public PublicApiConstructorAnnotatedInternalApi(NotAnnotated arg) {}
+}