refactor: Runner and App now use ? extends Plugin

core/src/main/java/com/google/adk/apps/App.java

@@ -17,7 +17,7 @@
 package com.google.adk.apps;
 
 import com.google.adk.agents.BaseAgent;
-import com.google.adk.plugins.BasePlugin;
+import com.google.adk.plugins.Plugin;
 import com.google.adk.summarizer.EventsCompactionConfig;
 import com.google.common.collect.ImmutableList;
 import com.google.errorprone.annotations.CanIgnoreReturnValue;
@@ -38,14 +38,14 @@ public class App {
 
   private final String name;
   private final BaseAgent rootAgent;
-  private final ImmutableList<BasePlugin> plugins;
+  private final ImmutableList<? extends Plugin> plugins;
   @Nullable private final EventsCompactionConfig eventsCompactionConfig;
   @Nullable private final ResumabilityConfig resumabilityConfig;
 
   private App(
       String name,
       BaseAgent rootAgent,
-      List<BasePlugin> plugins,
+      List<? extends Plugin> plugins,
       @Nullable EventsCompactionConfig eventsCompactionConfig,
       @Nullable ResumabilityConfig resumabilityConfig) {
     this.name = name;
@@ -63,7 +63,7 @@ public BaseAgent rootAgent() {
     return rootAgent;
   }
 
-  public ImmutableList<BasePlugin> plugins() {
+  public ImmutableList<? extends Plugin> plugins() {
     return plugins;
   }
 
@@ -81,7 +81,7 @@ public ResumabilityConfig resumabilityConfig() {
   public static class Builder {
     private String name;
     private BaseAgent rootAgent;
-    private List<BasePlugin> plugins = ImmutableList.of();
+    private List<? extends Plugin> plugins = ImmutableList.of();
     @Nullable private EventsCompactionConfig eventsCompactionConfig;
     @Nullable private ResumabilityConfig resumabilityConfig;
 
@@ -98,7 +98,7 @@ public Builder rootAgent(BaseAgent rootAgent) {
     }
 
     @CanIgnoreReturnValue
-    public Builder plugins(List<BasePlugin> plugins) {
+    public Builder plugins(List<? extends Plugin> plugins) {
       this.plugins = plugins;
       return this;
     }

core/src/main/java/com/google/adk/plugins/PluginManager.java

@@ -41,28 +41,21 @@
  * <p>The PluginManager is an internal class that orchestrates the invocation of plugin callbacks at
  * key points in the SDK's execution lifecycle.
  */
-public class PluginManager implements Plugin {
+public class PluginManager extends BasePlugin {
   private static final Logger logger = LoggerFactory.getLogger(PluginManager.class);
-  private final List<Plugin> plugins;
+  private final List<Plugin> plugins = new ArrayList<>();
 
   public PluginManager(List<? extends Plugin> plugins) {
-    this.plugins = new ArrayList<>();
+    super("PluginManager");
     if (plugins != null) {
-      for (var plugin : plugins) {
-        this.registerPlugin(plugin);
-      }
+      plugins.forEach(this::registerPlugin);
     }
   }
 
   public PluginManager() {
     this(null);
   }
 
-  @Override
-  public String getName() {
-    return "PluginManager";
-  }
-
   /**
    * Registers a new plugin.
    *

core/src/main/java/com/google/adk/runner/InMemoryRunner.java

@@ -19,7 +19,7 @@
 import com.google.adk.agents.BaseAgent;
 import com.google.adk.artifacts.InMemoryArtifactService;
 import com.google.adk.memory.InMemoryMemoryService;
-import com.google.adk.plugins.BasePlugin;
+import com.google.adk.plugins.Plugin;
 import com.google.adk.sessions.InMemorySessionService;
 import com.google.common.collect.ImmutableList;
 import java.util.List;
@@ -37,7 +37,7 @@ public InMemoryRunner(BaseAgent agent, String appName) {
     this(agent, appName, ImmutableList.of());
   }
 
-  public InMemoryRunner(BaseAgent agent, String appName, List<BasePlugin> plugins) {
+  public InMemoryRunner(BaseAgent agent, String appName, List<? extends Plugin> plugins) {
     super(
         agent,
         appName,

core/src/main/java/com/google/adk/runner/Runner.java

@@ -30,7 +30,7 @@
 import com.google.adk.events.EventActions;
 import com.google.adk.memory.BaseMemoryService;
 import com.google.adk.models.Model;
-import com.google.adk.plugins.BasePlugin;
+import com.google.adk.plugins.Plugin;
 import com.google.adk.plugins.PluginManager;
 import com.google.adk.sessions.BaseSessionService;
 import com.google.adk.sessions.InMemorySessionService;
@@ -84,7 +84,7 @@ public static class Builder {
     private BaseArtifactService artifactService = new InMemoryArtifactService();
     private BaseSessionService sessionService = new InMemorySessionService();
     @Nullable private BaseMemoryService memoryService = null;
-    private List<BasePlugin> plugins = ImmutableList.of();
+    private List<? extends Plugin> plugins = ImmutableList.of();
 
     @CanIgnoreReturnValue
     public Builder app(App app) {
@@ -126,7 +126,7 @@ public Builder memoryService(BaseMemoryService memoryService) {
     }
 
     @CanIgnoreReturnValue
-    public Builder plugins(List<BasePlugin> plugins) {
+    public Builder plugins(List<? extends Plugin> plugins) {
       Preconditions.checkState(this.app == null, "plugins() cannot be called when app is set.");
       this.plugins = plugins;
       return this;
@@ -135,7 +135,7 @@ public Builder plugins(List<BasePlugin> plugins) {
     public Runner build() {
       BaseAgent buildAgent;
       String buildAppName;
-      List<BasePlugin> buildPlugins;
+      List<? extends Plugin> buildPlugins;
       ResumabilityConfig buildResumabilityConfig;
       EventsCompactionConfig buildEventsCompactionConfig;
 
@@ -224,7 +224,7 @@ public Runner(
       BaseArtifactService artifactService,
       BaseSessionService sessionService,
       @Nullable BaseMemoryService memoryService,
-      List<BasePlugin> plugins) {
+      List<? extends Plugin> plugins) {
     this(
         agent,
         appName,
@@ -247,7 +247,7 @@ public Runner(
       BaseArtifactService artifactService,
       BaseSessionService sessionService,
       @Nullable BaseMemoryService memoryService,
-      List<BasePlugin> plugins,
+      List<? extends Plugin> plugins,
       ResumabilityConfig resumabilityConfig) {
     this(
         agent,
@@ -272,7 +272,7 @@ protected Runner(
       BaseArtifactService artifactService,
       BaseSessionService sessionService,
       @Nullable BaseMemoryService memoryService,
-      List<BasePlugin> plugins,
+      List<? extends Plugin> plugins,
       ResumabilityConfig resumabilityConfig,
       @Nullable EventsCompactionConfig eventsCompactionConfig) {
     this.agent = agent;