Allow removing plugin that's optionally extended

CHANGELOG.md

@@ -31,6 +31,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Fix SearchPhaseExecutionException to properly initCause ([#20320](https://github.com/opensearch-project/OpenSearch/pull/20320))
 - Fix `cluster.remote.<cluster_alias>.server_name` setting no populating SNI ([#20321](https://github.com/opensearch-project/OpenSearch/pull/20321))
 - Fix X-Opaque-Id header propagation (along with other response headers) for streaming Reactor Netty 4 transport ([#20371](https://github.com/opensearch-project/OpenSearch/pull/20371))
+- Allow removing plugin that's optionally extended ([#20417](https://github.com/opensearch-project/OpenSearch/pull/20417))
 - Fix indexing regression and bug fixes for grouping criteria. ([20145](https://github.com/opensearch-project/OpenSearch/pull/20145))
 
 ### Dependencies

distribution/tools/plugin-cli/src/main/java/org/opensearch/tools/cli/plugin/RemovePluginCommand.java

@@ -38,6 +38,7 @@
 import org.opensearch.cli.Terminal;
 import org.opensearch.cli.UserException;
 import org.opensearch.common.cli.EnvironmentAwareCommand;
+import org.opensearch.common.collect.Tuple;
 import org.opensearch.common.util.io.IOUtils;
 import org.opensearch.env.Environment;
 import org.opensearch.plugins.PluginsService;
@@ -98,13 +99,20 @@ void execute(Terminal terminal, Environment env, String pluginName, boolean purg
         }
 
         // first make sure nothing extends this plugin
-        List<String> usedBy = PluginsService.findPluginsByDependency(env.pluginsDir(), pluginName);
+        Tuple<List<String>, List<String>> dependents = PluginsService.findPluginsByDependency(env.pluginsDir(), pluginName);
+        List<String> usedBy = dependents.v1();
+        List<String> optionallyExtendedBy = dependents.v2();
         if (usedBy.isEmpty() == false) {
             throw new UserException(
                 PLUGIN_STILL_USED,
                 "plugin [" + pluginName + "] cannot be removed" + " because it is extended by other plugins: " + usedBy
             );
         }
+        if (optionallyExtendedBy.isEmpty() == false) {
+            terminal.println(
+                "WARNING: Some features of " + optionallyExtendedBy + " may not function without the dependency [" + pluginName + "]."
+            );
+        }
 
         Path pluginDir = env.pluginsDir().resolve(pluginName);
         Path pluginConfigDir = env.configDir().resolve(pluginName);

server/src/main/java/org/opensearch/plugins/PluginsService.java

@@ -405,17 +405,30 @@ public static void checkJarHellForPlugin(
         }
     }
 
-    public static List<String> findPluginsByDependency(Path pluginsDir, String pluginName) throws IOException {
-        List<String> usedBy = new ArrayList<>();
+    /**
+     * Finds plugins that depend on the given plugin.
+     *
+     * @param pluginsDir the plugins directory
+     * @param pluginName the plugin name to find dependents for
+     * @return a Tuple where v1() is the list of plugins with required dependencies,
+     *         and v2() is the list of plugins with optional dependencies
+     */
+    public static Tuple<List<String>, List<String>> findPluginsByDependency(Path pluginsDir, String pluginName) throws IOException {
+        List<String> requiredBy = new ArrayList<>();
+        List<String> optionallyExtendedBy = new ArrayList<>();
         Set<Bundle> bundles = getPluginBundles(pluginsDir);
         for (Bundle bundle : bundles) {
             for (String extendedPlugin : bundle.plugin.getExtendedPlugins()) {
                 if (extendedPlugin.equals(pluginName)) {
-                    usedBy.add(bundle.plugin.getName());
+                    if (bundle.plugin.isExtendedPluginOptional(extendedPlugin)) {
+                        optionallyExtendedBy.add(bundle.plugin.getName());
+                    } else {
+                        requiredBy.add(bundle.plugin.getName());
+                    }
                 }
             }
         }
-        return usedBy;
+        return new Tuple<>(requiredBy, optionallyExtendedBy);
     }
 
     /**

server/src/test/java/org/opensearch/plugins/PluginsServiceTests.java

@@ -1184,14 +1184,17 @@ public void testFindPluginsByDependency() throws Exception {
             "other-plugin"
         );
 
-        List<String> basePluginDependents = PluginsService.findPluginsByDependency(pluginsDir, "base-plugin");
-        assertThat(basePluginDependents, containsInAnyOrder("plugin1", "plugin2"));
+        Tuple<List<String>, List<String>> basePluginDependents = PluginsService.findPluginsByDependency(pluginsDir, "base-plugin");
+        assertThat(basePluginDependents.v1(), containsInAnyOrder("plugin1", "plugin2"));
+        assertTrue(basePluginDependents.v2().isEmpty());
 
-        List<String> otherPluginDependents = PluginsService.findPluginsByDependency(pluginsDir, "other-plugin");
-        assertThat(otherPluginDependents, containsInAnyOrder("plugin2", "plugin3"));
+        Tuple<List<String>, List<String>> otherPluginDependents = PluginsService.findPluginsByDependency(pluginsDir, "other-plugin");
+        assertThat(otherPluginDependents.v1(), containsInAnyOrder("plugin2", "plugin3"));
+        assertTrue(otherPluginDependents.v2().isEmpty());
 
-        List<String> nonExistentDependents = PluginsService.findPluginsByDependency(pluginsDir, "non-existent");
-        assertTrue(nonExistentDependents.isEmpty());
+        Tuple<List<String>, List<String>> nonExistentDependents = PluginsService.findPluginsByDependency(pluginsDir, "non-existent");
+        assertTrue(nonExistentDependents.v1().isEmpty());
+        assertTrue(nonExistentDependents.v2().isEmpty());
     }
 
     private PluginInfo getPluginInfoWithWithSemverRange(String semverRange) {