Migrate console to coreEvents.emitFeedback or debugLogger (#15219)

Author: Adib234

GEMINI.md

@@ -391,6 +391,15 @@ When working in the `/docs` directory, follow the guidelines in this section:
 Only write high-value comments if at all. Avoid talking to the user through
 comments.
 
+## Logging and Error Handling
+
+- **Avoid Console Statements:** Do not use `console.log`, `console.error`, or
+  similar methods directly.
+- **Non-User-Facing Logs:** For developer-facing debug messages, use
+  `debugLogger` (from `@google/gemini-cli-core`).
+- **User-Facing Feedback:** To surface errors or warnings to the user, use
+  `coreEvents.emitFeedback` (from `@google/gemini-cli-core`).
+
 ## General requirements
 
 - If there is something you do not understand or is ambiguous, seek confirmation

eslint.config.js

@@ -164,6 +164,7 @@ export default tseslint.config(
       'prefer-arrow-callback': 'error',
       'prefer-const': ['error', { destructuring: 'all' }],
       radix: 'error',
+      'no-console': 'error',
       'default-case': 'error',
       '@typescript-eslint/await-thenable': ['error'],
       '@typescript-eslint/no-floating-promises': ['error'],

packages/a2a-server/src/commands/command-registry.ts

@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
+import { debugLogger } from '@google/gemini-cli-core';
 import { ExtensionsCommand } from './extensions.js';
 import { InitCommand } from './init.js';
 import { RestoreCommand } from './restore.js';
@@ -20,7 +21,7 @@ class CommandRegistry {
 
   register(command: Command) {
     if (this.commands.has(command.name)) {
-      console.warn(`Command ${command.name} already registered. Skipping.`);
+      debugLogger.warn(`Command ${command.name} already registered. Skipping.`);
       return;
     }
 

packages/a2a-server/src/config/settings.test.ts

@@ -9,6 +9,7 @@ import * as fs from 'node:fs';
 import * as path from 'node:path';
 import * as os from 'node:os';
 import { loadSettings, USER_SETTINGS_PATH } from './settings.js';
+import { debugLogger } from '@google/gemini-cli-core';
 
 const mocks = vi.hoisted(() => {
   const suffix = Math.random().toString(36).slice(2);
@@ -75,7 +76,7 @@ describe('loadSettings', () => {
         fs.rmSync(mockWorkspaceDir, { recursive: true, force: true });
       }
     } catch (e) {
-      console.error('Failed to cleanup temp dirs', e);
+      debugLogger.error('Failed to cleanup temp dirs', e);
     }
     vi.restoreAllMocks();
   });

packages/a2a-server/src/http/app.ts

@@ -25,7 +25,7 @@ import { loadConfig, loadEnvironment, setTargetDir } from '../config/config.js';
 import { loadSettings } from '../config/settings.js';
 import { loadExtensions } from '../config/extension.js';
 import { commandRegistry } from '../commands/command-registry.js';
-import { SimpleExtensionLoader } from '@google/gemini-cli-core';
+import { debugLogger, SimpleExtensionLoader } from '@google/gemini-cli-core';
 import type { Command, CommandArgument } from '../commands/types.js';
 import { GitService } from '@google/gemini-cli-core';
 
@@ -239,7 +239,7 @@ export async function createApp() {
         ): CommandResponse | undefined => {
           const commandName = command.name;
           if (visited.includes(commandName)) {
-            console.warn(
+            debugLogger.warn(
               `Command ${commandName} already inserted in the response, skipping`,
             );
             return undefined;

packages/cli/src/gemini.test.tsx

@@ -29,6 +29,7 @@ import {
   type Config,
   type ResumedSessionData,
   debugLogger,
+  coreEvents,
 } from '@google/gemini-cli-core';
 import { act } from 'react';
 import { type InitializationResult } from './core/initializer.js';
@@ -819,9 +820,7 @@ describe('gemini.tsx main function kitty protocol', () => {
       .mockImplementation((code) => {
         throw new MockProcessExitError(code);
       });
-    const consoleErrorSpy = vi
-      .spyOn(console, 'error')
-      .mockImplementation(() => {});
+    const emitFeedbackSpy = vi.spyOn(coreEvents, 'emitFeedback');
 
     vi.mocked(loadSettings).mockReturnValue({
       merged: { advanced: {}, security: { auth: {} }, ui: { theme: 'test' } },
@@ -875,12 +874,13 @@ describe('gemini.tsx main function kitty protocol', () => {
       if (!(e instanceof MockProcessExitError)) throw e;
     }
 
-    expect(consoleErrorSpy).toHaveBeenCalledWith(
+    expect(emitFeedbackSpy).toHaveBeenCalledWith(
+      'error',
       expect.stringContaining('Error resuming session: Session not found'),
     );
     expect(processExitSpy).toHaveBeenCalledWith(42);
     processExitSpy.mockRestore();
-    consoleErrorSpy.mockRestore();
+    emitFeedbackSpy.mockRestore();
   });
 
   it.skip('should log error when cleanupExpiredSessions fails', async () => {

packages/cli/src/gemini.tsx

@@ -41,6 +41,7 @@ import {
   type ResumedSessionData,
   type OutputPayload,
   type ConsoleLogPayload,
+  type UserFeedbackPayload,
   sessionId,
   logUserPrompt,
   AuthType,
@@ -597,7 +598,8 @@ export async function main() {
         // Use the existing session ID to continue recording to the same session
         config.setSessionId(resumedSessionData.conversation.sessionId);
       } catch (error) {
-        console.error(
+        coreEvents.emitFeedback(
+          'error',
           `Error resuming session: ${error instanceof Error ? error.message : 'Unknown error'}`,
         );
         await runExitCleanup();
@@ -719,13 +721,25 @@ export function initializeOutputListenersAndFlush() {
       }
     });
 
-    coreEvents.on(CoreEvent.ConsoleLog, (payload: ConsoleLogPayload) => {
-      if (payload.type === 'error' || payload.type === 'warn') {
-        writeToStderr(payload.content);
-      } else {
-        writeToStdout(payload.content);
-      }
-    });
+    if (coreEvents.listenerCount(CoreEvent.ConsoleLog) === 0) {
+      coreEvents.on(CoreEvent.ConsoleLog, (payload: ConsoleLogPayload) => {
+        if (payload.type === 'error' || payload.type === 'warn') {
+          writeToStderr(payload.content);
+        } else {
+          writeToStdout(payload.content);
+        }
+      });
+    }
+
+    if (coreEvents.listenerCount(CoreEvent.UserFeedback) === 0) {
+      coreEvents.on(CoreEvent.UserFeedback, (payload: UserFeedbackPayload) => {
+        if (payload.severity === 'error' || payload.severity === 'warning') {
+          writeToStderr(payload.message);
+        } else {
+          writeToStdout(payload.message);
+        }
+      });
+    }
   }
   coreEvents.drainBacklogs();
 }

packages/cli/src/nonInteractiveCli.test.ts

@@ -44,6 +44,7 @@ const mockCoreEvents = vi.hoisted(() => ({
   off: vi.fn(),
   drainBacklogs: vi.fn(),
   emit: vi.fn(),
+  emitFeedback: vi.fn(),
 }));
 
 vi.mock('@google/gemini-cli-core', async (importOriginal) => {
@@ -785,11 +786,6 @@ describe('runNonInteractive', () => {
       throw testError;
     });
 
-    // Mock console.error to capture JSON error output
-    const consoleErrorJsonSpy = vi
-      .spyOn(console, 'error')
-      .mockImplementation(() => {});
-
     let thrownError: Error | null = null;
     try {
       await runNonInteractive({
@@ -807,7 +803,8 @@ describe('runNonInteractive', () => {
     // Should throw because of mocked process.exit
     expect(thrownError?.message).toBe('process.exit(1) called');
 
-    expect(consoleErrorJsonSpy).toHaveBeenCalledWith(
+    expect(mockCoreEvents.emitFeedback).toHaveBeenCalledWith(
+      'error',
       JSON.stringify(
         {
           session_id: 'test-session-id',
@@ -831,11 +828,6 @@ describe('runNonInteractive', () => {
       throw fatalError;
     });
 
-    // Mock console.error to capture JSON error output
-    const consoleErrorJsonSpy = vi
-      .spyOn(console, 'error')
-      .mockImplementation(() => {});
-
     let thrownError: Error | null = null;
     try {
       await runNonInteractive({
@@ -853,7 +845,8 @@ describe('runNonInteractive', () => {
     // Should throw because of mocked process.exit with custom exit code
     expect(thrownError?.message).toBe('process.exit(42) called');
 
-    expect(consoleErrorJsonSpy).toHaveBeenCalledWith(
+    expect(mockCoreEvents.emitFeedback).toHaveBeenCalledWith(
+      'error',
       JSON.stringify(
         {
           session_id: 'test-session-id',

packages/cli/src/services/FileCommandLoader.ts

@@ -10,7 +10,7 @@ import toml from '@iarna/toml';
 import { glob } from 'glob';
 import { z } from 'zod';
 import type { Config } from '@google/gemini-cli-core';
-import { Storage } from '@google/gemini-cli-core';
+import { Storage, coreEvents } from '@google/gemini-cli-core';
 import type { ICommandLoader } from './types.js';
 import type {
   CommandContext,
@@ -126,7 +126,8 @@ export class FileCommandLoader implements ICommandLoader {
           !signal.aborted &&
           (error as { code?: string })?.code !== 'ENOENT'
         ) {
-          console.error(
+          coreEvents.emitFeedback(
+            'error',
             `[FileCommandLoader] Error loading commands from ${dirInfo.path}:`,
             error,
           );
@@ -189,7 +190,8 @@ export class FileCommandLoader implements ICommandLoader {
     try {
       fileContent = await fs.readFile(filePath, 'utf-8');
     } catch (error: unknown) {
-      console.error(
+      coreEvents.emitFeedback(
+        'error',
         `[FileCommandLoader] Failed to read file ${filePath}:`,
         error instanceof Error ? error.message : String(error),
       );
@@ -200,7 +202,8 @@ export class FileCommandLoader implements ICommandLoader {
     try {
       parsed = toml.parse(fileContent);
     } catch (error: unknown) {
-      console.error(
+      coreEvents.emitFeedback(
+        'error',
         `[FileCommandLoader] Failed to parse TOML file ${filePath}:`,
         error instanceof Error ? error.message : String(error),
       );
@@ -210,7 +213,8 @@ export class FileCommandLoader implements ICommandLoader {
     const validationResult = TomlCommandDefSchema.safeParse(parsed);
 
     if (!validationResult.success) {
-      console.error(
+      coreEvents.emitFeedback(
+        'error',
         `[FileCommandLoader] Skipping invalid command file: ${filePath}. Validation errors:`,
         validationResult.error.flatten(),
       );
@@ -278,7 +282,8 @@ export class FileCommandLoader implements ICommandLoader {
         _args: string,
       ): Promise<SlashCommandActionReturn> => {
         if (!context.invocation) {
-          console.error(
+          coreEvents.emitFeedback(
+            'error',
             `[FileCommandLoader] Critical error: Command '${baseCommandName}' was executed without invocation context.`,
           );
           return {

packages/cli/src/ui/AppContainer.tsx

@@ -842,16 +842,8 @@ Logging in with Google... Restarting Gemini CLI to continue.
   const handleClearScreen = useCallback(() => {
     historyManager.clearItems();
     clearConsoleMessagesState();
-    if (!isAlternateBuffer) {
-      console.clear();
-    }
     refreshStatic();
-  }, [
-    historyManager,
-    clearConsoleMessagesState,
-    refreshStatic,
-    isAlternateBuffer,
-  ]);
+  }, [historyManager, clearConsoleMessagesState, refreshStatic]);
 
   const { handleInput: vimHandleInput } = useVim(buffer, handleFinalSubmit);