feat: Improving LoggingPlugin

This CL refactors and improves the `LoggingPlugin` in the ADK core.

Here's a summary of the changes:

1.  **Consistent Agent Name Logging**: The plugin now consistently retrieves the agent name from `callbackContext.agentName()` in `beforeAgentCallback` and `afterAgentCallback`, instead of using `agent.name()`.

2.  **Enhanced LLM Response Logging**: The `formatContent` method has been significantly updated to provide more detailed logging for different types of `Content.parts()` within an LLM response. It now explicitly logs:
    *   Trimmed and potentially truncated text.
    *   The name of `functionCall` and `functionResponse`.
    *   Indicators for `codeExecutionResult` and other part types.
    The different parts are joined by " | ".

3.  **Improved Optional Field Logging**: Optional fields like `llmResponse.errorMessage()` and `toolContext.functionCallId()` are now always logged, displaying "None" when the optional is empty, rather than only logging when the value is present.

4.  **Simplified Argument Formatting**: The `formatArgs` method now uses `args.toString()` for formatting, simplifying the code while still handling truncation for long argument strings.

5.  **Removed Redundant Error Logging**: Duplicate `logger.error` calls within `onLlmError` and `onToolError` have been removed, as the preceding `log` calls already capture the necessary error information.

6.  **Test Updates**: `LoggingPluginTest.java` has been updated to mock `mockCallbackContext.invocationContext()` and remove an unnecessary mock for `mockCallbackContext.branch()`.

PiperOrigin-RevId: 859611274

Author: google-genai-bot

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

@@ -133,7 +133,7 @@ public Maybe<Content> beforeAgentCallback(BaseAgent agent, CallbackContext callb
     return Maybe.fromAction(
         () -> {
           log("🤖 AGENT STARTING");
-          log("   Agent Name: " + agent.name());
+          log("   Agent Name: " + callbackContext.agentName());
           log("   Invocation ID: " + callbackContext.invocationId());
           callbackContext.branch().ifPresent(branch -> log("   Branch: " + branch));
         });
@@ -144,7 +144,7 @@ public Maybe<Content> afterAgentCallback(BaseAgent agent, CallbackContext callba
     return Maybe.fromAction(
         () -> {
           log("🤖 AGENT COMPLETED");
-          log("   Agent Name: " + agent.name());
+          log("   Agent Name: " + callbackContext.agentName());
           log("   Invocation ID: " + callbackContext.invocationId());
         });
   }
@@ -188,7 +188,7 @@ public Maybe<LlmResponse> afterModelCallback(
 
           if (llmResponse.errorCode().isPresent()) {
             log("   ❌ ERROR - Code: " + llmResponse.errorCode().get());
-            llmResponse.errorMessage().ifPresent(msg -> log("   Error Message: " + msg));
+            log("   Error Message: " + llmResponse.errorMessage().orElse("None"));
           } else {
             log("   Content: " + formatContent(llmResponse.content()));
             llmResponse.partial().ifPresent(partial -> log("   Partial: " + partial));
@@ -230,7 +230,7 @@ public Maybe<Map<String, Object>> beforeToolCallback(
           log("🔧 TOOL STARTING");
           log("   Tool Name: " + tool.name());
           log("   Agent: " + toolContext.agentName());
-          toolContext.functionCallId().ifPresent(id -> log("   Function Call ID: " + id));
+          log("   Function Call ID: " + toolContext.functionCallId().orElse("None"));
           log("   Arguments: " + formatArgs(toolArgs));
         });
   }
@@ -246,7 +246,7 @@ public Maybe<Map<String, Object>> afterToolCallback(
           log("🔧 TOOL COMPLETED");
           log("   Tool Name: " + tool.name());
           log("   Agent: " + toolContext.agentName());
-          toolContext.functionCallId().ifPresent(id -> log("   Function Call ID: " + id));
+          log("   Function Call ID: " + toolContext.functionCallId().orElse("None"));
           log("   Result: " + formatArgs(result));
         });
   }
@@ -259,10 +259,9 @@ public Maybe<Map<String, Object>> onToolErrorCallback(
           log("🔧 TOOL ERROR");
           log("   Tool Name: " + tool.name());
           log("   Agent: " + toolContext.agentName());
-          toolContext.functionCallId().ifPresent(id -> log("   Function Call ID: " + id));
+          log("   Function Call ID: " + toolContext.functionCallId().orElse("None"));
           log("   Arguments: " + formatArgs(toolArgs));
           log("   Error: " + error.getMessage());
-          logger.error("[{}] Tool Error", name, error);
         });
   }
 
@@ -274,30 +273,36 @@ private String formatContent(Optional<Content> contentOptional) {
     if (content.parts().isEmpty() || content.parts().get().isEmpty()) {
       return "None";
     }
-
-    String combinedText =
-        content.parts().get().stream()
-            .map(part -> part.text().orElse(""))
-            .collect(joining("\n"))
-            .trim();
-
-    if (combinedText.length() > MAX_CONTENT_LENGTH) {
-      return combinedText.substring(0, MAX_CONTENT_LENGTH) + "...";
-    }
-    return combinedText;
+    return content.parts().get().stream()
+        .map(
+            part -> {
+              if (part.text().isPresent()) {
+                String text = part.text().get().trim();
+                if (text.length() > MAX_CONTENT_LENGTH) {
+                  text = text.substring(0, MAX_CONTENT_LENGTH) + "...";
+                }
+                return String.format("text: '%s'", text);
+              } else if (part.functionCall().isPresent()) {
+                return String.format("function_call: %s", part.functionCall().get().name());
+              } else if (part.functionResponse().isPresent()) {
+                return String.format("function_response: %s", part.functionResponse().get().name());
+              } else if (part.codeExecutionResult().isPresent()) {
+                return "code_execution_result";
+              } else {
+                return "other_part";
+              }
+            })
+        .collect(joining("\n"));
   }
 
   private String formatArgs(Map<String, Object> args) {
     if (args == null || args.isEmpty()) {
       return "{}";
     }
-    String argsStr =
-        args.entrySet().stream()
-            .map(entry -> entry.getKey() + "=" + entry.getValue())
-            .collect(joining(", "));
-    if (argsStr.length() > MAX_ARGS_LENGTH) {
-      return "{" + argsStr.substring(0, MAX_ARGS_LENGTH) + "...}";
+    String formatted = args.toString();
+    if (formatted.length() > MAX_ARGS_LENGTH) {
+      formatted = formatted.substring(0, MAX_ARGS_LENGTH) + "...}";
     }
-    return "{" + argsStr + "}";
+    return formatted;
   }
 }

core/src/test/java/com/google/adk/plugins/LoggingPluginTest.java

@@ -87,7 +87,7 @@ public void setUp() {
 
     when(mockCallbackContext.invocationId()).thenReturn("invocation_id");
     when(mockCallbackContext.agentName()).thenReturn("agent_name");
-    when(mockCallbackContext.branch()).thenReturn(Optional.empty());
+    when(mockCallbackContext.invocationContext()).thenReturn(mockInvocationContext);
 
     when(mockTool.name()).thenReturn("tool_name");
     when(mockToolContext.agentName()).thenReturn("agent_name");