feat: allow custom filename for context files (#654)

Co-authored-by: N. Taylor Mullen <ntaylormullen@google.com>

packages/cli/src/config/config.ts

@@ -13,6 +13,8 @@ import {
   createServerConfig,
   loadServerHierarchicalMemory,
   ConfigParameters,
+  setGeminiMdFilename as setServerGeminiMdFilename,
+  getCurrentGeminiMdFilename,
 } from '@gemini-code/core';
 import { Settings } from './settings.js';
 import { readPackageUp } from 'read-package-up';
@@ -132,6 +134,17 @@ export async function loadCliConfig(settings: Settings): Promise<Config> {
   const argv = await parseArguments();
   const debugMode = argv.debug || false;
 
+  // Set the context filename in the server's memoryTool module BEFORE loading memory
+  // TODO(b/343434939): This is a bit of a hack. The contextFileName should ideally be passed
+  // directly to the Config constructor in core, and have core handle setGeminiMdFilename.
+  // However, loadHierarchicalGeminiMemory is called *before* createServerConfig.
+  if (settings.contextFileName) {
+    setServerGeminiMdFilename(settings.contextFileName);
+  } else {
+    // Reset to default if not provided in settings.
+    setServerGeminiMdFilename(getCurrentGeminiMdFilename());
+  }
+
   // Call the (now wrapper) loadHierarchicalGeminiMemory which calls the server's version
   const { memoryContent, fileCount } = await loadHierarchicalGeminiMemory(
     process.cwd(),
@@ -159,7 +172,8 @@ export async function loadCliConfig(settings: Settings): Promise<Config> {
     userMemory: memoryContent,
     geminiMdFileCount: fileCount,
     vertexai: useVertexAI,
-    showMemoryUsage: argv.show_memory_usage || false,
+    showMemoryUsage:
+      argv.show_memory_usage || settings.showMemoryUsage || false,
   };
 
   return createServerConfig(configParams);

packages/cli/src/config/settings.test.ts

@@ -0,0 +1,309 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/// <reference types="vitest/globals" />
+
+const MOCK_HOME_DIR = '/mock/home/user'; // MUST BE FIRST
+
+// Mock 'os' first. Its factory uses MOCK_HOME_DIR.
+import * as osActual from 'os'; // Import for type info for the mock factory
+vi.mock('os', async (importOriginal) => {
+  const actualOs = await importOriginal<typeof osActual>();
+  return {
+    ...actualOs,
+    homedir: vi.fn(() => MOCK_HOME_DIR),
+  };
+});
+
+// Mock './settings.js' to ensure it uses the mocked 'os.homedir()' for its internal constants.
+vi.mock('./settings.js', async (importActual) => {
+  const originalModule = await importActual<typeof import('./settings.js')>();
+  return {
+    __esModule: true, // Ensure correct module shape
+    ...originalModule, // Re-export all original members
+    // We are relying on originalModule's USER_SETTINGS_PATH being constructed with mocked os.homedir()
+  };
+});
+
+// NOW import everything else, including the (now effectively re-exported) settings.js
+import * as pathActual from 'path'; // Restored for MOCK_WORKSPACE_SETTINGS_PATH
+import {
+  describe,
+  it,
+  expect,
+  vi,
+  beforeEach,
+  afterEach,
+  type Mocked,
+  type Mock,
+} from 'vitest';
+import * as fs from 'fs'; // fs will be mocked separately
+import stripJsonComments from 'strip-json-comments'; // Will be mocked separately
+
+// These imports will get the versions from the vi.mock('./settings.js', ...) factory.
+import {
+  LoadedSettings,
+  loadSettings,
+  USER_SETTINGS_PATH, // This IS the mocked path.
+  SETTINGS_DIRECTORY_NAME, // This is from the original module, but used by the mock.
+  SettingScope,
+} from './settings.js';
+
+const MOCK_WORKSPACE_DIR = '/mock/workspace';
+// Use the (mocked) SETTINGS_DIRECTORY_NAME for consistency
+const MOCK_WORKSPACE_SETTINGS_PATH = pathActual.join(
+  MOCK_WORKSPACE_DIR,
+  SETTINGS_DIRECTORY_NAME,
+  'settings.json',
+);
+
+vi.mock('fs');
+vi.mock('strip-json-comments', () => ({
+  default: vi.fn((content) => content),
+}));
+
+describe('Settings Loading and Merging', () => {
+  let mockFsExistsSync: Mocked<typeof fs.existsSync>;
+  let mockStripJsonComments: Mocked<typeof stripJsonComments>;
+  let mockFsMkdirSync: Mocked<typeof fs.mkdirSync>;
+
+  beforeEach(() => {
+    vi.resetAllMocks();
+
+    mockFsExistsSync = vi.mocked(fs.existsSync);
+    mockFsMkdirSync = vi.mocked(fs.mkdirSync);
+    mockStripJsonComments = vi.mocked(stripJsonComments);
+
+    vi.mocked(osActual.homedir).mockReturnValue(MOCK_HOME_DIR);
+    (mockStripJsonComments as unknown as Mock).mockImplementation(
+      (jsonString: string) => jsonString,
+    );
+    (mockFsExistsSync as Mock).mockReturnValue(false);
+    (fs.readFileSync as Mock).mockReturnValue('{}'); // Return valid empty JSON
+    (mockFsMkdirSync as Mock).mockImplementation(() => undefined);
+  });
+
+  afterEach(() => {
+    vi.restoreAllMocks();
+  });
+
+  describe('loadSettings', () => {
+    it('should load empty settings if no files exist', () => {
+      const settings = loadSettings(MOCK_WORKSPACE_DIR);
+      expect(settings.user.settings).toEqual({});
+      expect(settings.workspace.settings).toEqual({});
+      expect(settings.merged).toEqual({});
+    });
+
+    it('should load user settings if only user file exists', () => {
+      const expectedUserSettingsPath = USER_SETTINGS_PATH; // Use the path actually resolved by the (mocked) module
+
+      (mockFsExistsSync as Mock).mockImplementation(
+        (p: fs.PathLike) => p === expectedUserSettingsPath,
+      );
+      const userSettingsContent = {
+        theme: 'dark',
+        contextFileName: 'USER_CONTEXT.md',
+      };
+      (fs.readFileSync as Mock).mockImplementation(
+        (p: fs.PathOrFileDescriptor) => {
+          if (p === expectedUserSettingsPath)
+            return JSON.stringify(userSettingsContent);
+          return '{}';
+        },
+      );
+
+      const settings = loadSettings(MOCK_WORKSPACE_DIR);
+
+      expect(fs.readFileSync).toHaveBeenCalledWith(
+        expectedUserSettingsPath,
+        'utf-8',
+      );
+      expect(settings.user.settings).toEqual(userSettingsContent);
+      expect(settings.workspace.settings).toEqual({});
+      expect(settings.merged).toEqual(userSettingsContent);
+    });
+
+    it('should load workspace settings if only workspace file exists', () => {
+      (mockFsExistsSync as Mock).mockImplementation(
+        (p: fs.PathLike) => p === MOCK_WORKSPACE_SETTINGS_PATH,
+      );
+      const workspaceSettingsContent = {
+        sandbox: true,
+        contextFileName: 'WORKSPACE_CONTEXT.md',
+      };
+      (fs.readFileSync as Mock).mockImplementation(
+        (p: fs.PathOrFileDescriptor) => {
+          if (p === MOCK_WORKSPACE_SETTINGS_PATH)
+            return JSON.stringify(workspaceSettingsContent);
+          return '';
+        },
+      );
+
+      const settings = loadSettings(MOCK_WORKSPACE_DIR);
+
+      expect(fs.readFileSync).toHaveBeenCalledWith(
+        MOCK_WORKSPACE_SETTINGS_PATH,
+        'utf-8',
+      );
+      expect(settings.user.settings).toEqual({});
+      expect(settings.workspace.settings).toEqual(workspaceSettingsContent);
+      expect(settings.merged).toEqual(workspaceSettingsContent);
+    });
+
+    it('should merge user and workspace settings, with workspace taking precedence', () => {
+      (mockFsExistsSync as Mock).mockReturnValue(true);
+      const userSettingsContent = {
+        theme: 'dark',
+        sandbox: false,
+        contextFileName: 'USER_CONTEXT.md',
+      };
+      const workspaceSettingsContent = {
+        sandbox: true,
+        coreTools: ['tool1'],
+        contextFileName: 'WORKSPACE_CONTEXT.md',
+      };
+
+      (fs.readFileSync as Mock).mockImplementation(
+        (p: fs.PathOrFileDescriptor) => {
+          if (p === USER_SETTINGS_PATH)
+            return JSON.stringify(userSettingsContent);
+          if (p === MOCK_WORKSPACE_SETTINGS_PATH)
+            return JSON.stringify(workspaceSettingsContent);
+          return '';
+        },
+      );
+
+      const settings = loadSettings(MOCK_WORKSPACE_DIR);
+
+      expect(settings.user.settings).toEqual(userSettingsContent);
+      expect(settings.workspace.settings).toEqual(workspaceSettingsContent);
+      expect(settings.merged).toEqual({
+        theme: 'dark',
+        sandbox: true,
+        coreTools: ['tool1'],
+        contextFileName: 'WORKSPACE_CONTEXT.md',
+      });
+    });
+
+    it('should handle contextFileName correctly when only in user settings', () => {
+      (mockFsExistsSync as Mock).mockImplementation(
+        (p: fs.PathLike) => p === USER_SETTINGS_PATH,
+      );
+      const userSettingsContent = { contextFileName: 'CUSTOM.md' };
+      (fs.readFileSync as Mock).mockImplementation(
+        (p: fs.PathOrFileDescriptor) => {
+          if (p === USER_SETTINGS_PATH)
+            return JSON.stringify(userSettingsContent);
+          return '';
+        },
+      );
+
+      const settings = loadSettings(MOCK_WORKSPACE_DIR);
+      expect(settings.merged.contextFileName).toBe('CUSTOM.md');
+    });
+
+    it('should handle contextFileName correctly when only in workspace settings', () => {
+      (mockFsExistsSync as Mock).mockImplementation(
+        (p: fs.PathLike) => p === MOCK_WORKSPACE_SETTINGS_PATH,
+      );
+      const workspaceSettingsContent = {
+        contextFileName: 'PROJECT_SPECIFIC.md',
+      };
+      (fs.readFileSync as Mock).mockImplementation(
+        (p: fs.PathOrFileDescriptor) => {
+          if (p === MOCK_WORKSPACE_SETTINGS_PATH)
+            return JSON.stringify(workspaceSettingsContent);
+          return '';
+        },
+      );
+
+      const settings = loadSettings(MOCK_WORKSPACE_DIR);
+      expect(settings.merged.contextFileName).toBe('PROJECT_SPECIFIC.md');
+    });
+
+    it('should default contextFileName to undefined if not in any settings file', () => {
+      (mockFsExistsSync as Mock).mockReturnValue(true);
+      const userSettingsContent = { theme: 'dark' };
+      const workspaceSettingsContent = { sandbox: true };
+      (fs.readFileSync as Mock).mockImplementation(
+        (p: fs.PathOrFileDescriptor) => {
+          if (p === USER_SETTINGS_PATH)
+            return JSON.stringify(userSettingsContent);
+          if (p === MOCK_WORKSPACE_SETTINGS_PATH)
+            return JSON.stringify(workspaceSettingsContent);
+          return '';
+        },
+      );
+
+      const settings = loadSettings(MOCK_WORKSPACE_DIR);
+      expect(settings.merged.contextFileName).toBeUndefined();
+    });
+
+    it('should handle JSON parsing errors gracefully', () => {
+      (mockFsExistsSync as Mock).mockReturnValue(true);
+      (fs.readFileSync as Mock).mockImplementation(
+        (p: fs.PathOrFileDescriptor) => {
+          // Make it return invalid json for the paths it will try to read
+          if (p === USER_SETTINGS_PATH || p === MOCK_WORKSPACE_SETTINGS_PATH)
+            return 'invalid json';
+          return '';
+        },
+      );
+      const consoleErrorSpy = vi
+        .spyOn(console, 'error')
+        .mockImplementation(() => {});
+
+      const settings = loadSettings(MOCK_WORKSPACE_DIR);
+
+      expect(settings.user.settings).toEqual({});
+      expect(settings.workspace.settings).toEqual({});
+      expect(settings.merged).toEqual({});
+      expect(consoleErrorSpy).toHaveBeenCalledTimes(2);
+
+      consoleErrorSpy.mockRestore();
+    });
+  });
+
+  describe('LoadedSettings class', () => {
+    it('setValue should update the correct scope and recompute merged settings', () => {
+      (mockFsExistsSync as Mock).mockReturnValue(false);
+      const loadedSettings = loadSettings(MOCK_WORKSPACE_DIR) as LoadedSettings;
+
+      vi.mocked(fs.writeFileSync).mockImplementation(() => {});
+      // mkdirSync is mocked in beforeEach to return undefined, which is fine for void usage
+
+      loadedSettings.setValue(SettingScope.User, 'theme', 'matrix');
+      expect(loadedSettings.user.settings.theme).toBe('matrix');
+      expect(loadedSettings.merged.theme).toBe('matrix');
+      expect(fs.writeFileSync).toHaveBeenCalledWith(
+        USER_SETTINGS_PATH,
+        JSON.stringify({ theme: 'matrix' }, null, 2),
+        'utf-8',
+      );
+
+      loadedSettings.setValue(
+        SettingScope.Workspace,
+        'contextFileName',
+        'MY_AGENTS.md',
+      );
+      expect(loadedSettings.workspace.settings.contextFileName).toBe(
+        'MY_AGENTS.md',
+      );
+      expect(loadedSettings.merged.contextFileName).toBe('MY_AGENTS.md');
+      expect(loadedSettings.merged.theme).toBe('matrix');
+      expect(fs.writeFileSync).toHaveBeenCalledWith(
+        MOCK_WORKSPACE_SETTINGS_PATH,
+        JSON.stringify({ contextFileName: 'MY_AGENTS.md' }, null, 2),
+        'utf-8',
+      );
+
+      loadedSettings.setValue(SettingScope.Workspace, 'theme', 'ocean');
+      expect(loadedSettings.workspace.settings.theme).toBe('ocean');
+      expect(loadedSettings.merged.theme).toBe('ocean');
+    });
+  });
+});

packages/cli/src/config/settings.ts

@@ -30,6 +30,7 @@ export interface Settings {
   mcpServerCommand?: string;
   mcpServers?: Record<string, MCPServerConfig>;
   showMemoryUsage?: boolean;
+  contextFileName?: string;
   // Add other settings here.
 }