feat(cli): respect the NO_COLOR env variable (#772)

packages/cli/src/ui/App.test.tsx

@@ -15,6 +15,7 @@ import {
   AccessibilitySettings,
 } from '@gemini-code/core';
 import { LoadedSettings, SettingsFile, Settings } from '../config/settings.js';
+import process from 'node:process';
 
 // Define a more complete mock server config based on actual Config
 interface MockServerConfig {
@@ -345,20 +346,52 @@ describe('App UI', () => {
     expect(lastFrame()).toContain('Using 2 MCP servers');
   });
 
-  it('should display theme dialog if no theme is set in settings', async () => {
-    mockSettings = createMockSettings({});
-    mockConfig.getDebugMode.mockReturnValue(false);
-    mockConfig.getShowMemoryUsage.mockReturnValue(false);
+  describe('when no theme is set', () => {
+    let originalNoColor: string | undefined;
 
-    const { lastFrame, unmount } = render(
-      <App
-        config={mockConfig as unknown as ServerConfig}
-        settings={mockSettings}
-        cliVersion="1.0.0"
-      />,
-    );
-    currentUnmount = unmount;
+    beforeEach(() => {
+      originalNoColor = process.env.NO_COLOR;
+      // Ensure no theme is set for these tests
+      mockSettings = createMockSettings({});
+      mockConfig.getDebugMode.mockReturnValue(false);
+      mockConfig.getShowMemoryUsage.mockReturnValue(false);
+    });
 
-    expect(lastFrame()).toContain('Select Theme');
+    afterEach(() => {
+      process.env.NO_COLOR = originalNoColor;
+    });
+
+    it('should display theme dialog if NO_COLOR is not set', async () => {
+      delete process.env.NO_COLOR;
+
+      const { lastFrame, unmount } = render(
+        <App
+          config={mockConfig as unknown as ServerConfig}
+          settings={mockSettings}
+          cliVersion="1.0.0"
+        />,
+      );
+      currentUnmount = unmount;
+
+      expect(lastFrame()).toContain('Select Theme');
+    });
+
+    it('should display a message if NO_COLOR is set', async () => {
+      process.env.NO_COLOR = 'true';
+
+      const { lastFrame, unmount } = render(
+        <App
+          config={mockConfig as unknown as ServerConfig}
+          settings={mockSettings}
+          cliVersion="1.0.0"
+        />,
+      );
+      currentUnmount = unmount;
+
+      expect(lastFrame()).toContain(
+        'Theme configuration unavailable due to NO_COLOR env variable.',
+      );
+      expect(lastFrame()).not.toContain('Select Theme');
+    });
   });
 });

packages/cli/src/ui/App.tsx

@@ -136,7 +136,7 @@ export const App = ({
     openThemeDialog,
     handleThemeSelect,
     handleThemeHighlight,
-  } = useThemeCommand(settings, setThemeError);
+  } = useThemeCommand(settings, setThemeError, addItem);
 
   useEffect(() => {
     if (config) {

packages/cli/src/ui/hooks/useThemeCommand.ts

@@ -7,6 +7,8 @@
 import { useState, useCallback, useEffect } from 'react';
 import { themeManager } from '../themes/theme-manager.js';
 import { LoadedSettings, SettingScope } from '../../config/settings.js'; // Import LoadedSettings, AppSettings, MergedSetting
+import { type HistoryItem, MessageType } from '../types.js';
+import process from 'node:process';
 
 interface UseThemeCommandReturn {
   isThemeDialogOpen: boolean;
@@ -21,34 +23,55 @@ interface UseThemeCommandReturn {
 export const useThemeCommand = (
   loadedSettings: LoadedSettings,
   setThemeError: (error: string | null) => void,
+  addItem: (item: Omit<HistoryItem, 'id'>, timestamp: number) => void,
 ): UseThemeCommandReturn => {
   // Determine the effective theme
   const effectiveTheme = loadedSettings.merged.theme;
 
   // Initial state: Open dialog if no theme is set in either user or workspace settings
   const [isThemeDialogOpen, setIsThemeDialogOpen] = useState(
-    effectiveTheme === undefined, // Open dialog if no theme is set initially
+    effectiveTheme === undefined && !process.env.NO_COLOR,
   );
   // TODO: refactor how theme's are accessed to avoid requiring a forced render.
   const [, setForceRender] = useState(0);
 
   // Apply initial theme on component mount
   useEffect(() => {
-    // Only try to set a theme if one is actually defined.
-    // If effectiveTheme was undefined, the dialog is already open due to useState above.
-    if (effectiveTheme !== undefined) {
-      if (!themeManager.setActiveTheme(effectiveTheme)) {
-        setIsThemeDialogOpen(true);
-        setThemeError(`Theme "${effectiveTheme}" not found.`);
-      } else {
-        setThemeError(null); // Clear any previous theme error on success
+    if (effectiveTheme === undefined) {
+      if (process.env.NO_COLOR) {
+        addItem(
+          {
+            type: MessageType.INFO,
+            text: 'Theme configuration unavailable due to NO_COLOR env variable.',
+          },
+          Date.now(),
+        );
       }
+      // If no theme is set and NO_COLOR is not set, the dialog is already open.
+      return;
     }
-  }, [effectiveTheme, setThemeError]); // Re-run if effectiveTheme or setThemeError changes
+
+    if (!themeManager.setActiveTheme(effectiveTheme)) {
+      setIsThemeDialogOpen(true);
+      setThemeError(`Theme "${effectiveTheme}" not found.`);
+    } else {
+      setThemeError(null);
+    }
+  }, [effectiveTheme, setThemeError, addItem]); // Re-run if effectiveTheme or setThemeError changes
 
   const openThemeDialog = useCallback(() => {
+    if (process.env.NO_COLOR) {
+      addItem(
+        {
+          type: MessageType.INFO,
+          text: 'Theme configuration unavailable due to NO_COLOR env variable.',
+        },
+        Date.now(),
+      );
+      return;
+    }
     setIsThemeDialogOpen(true);
-  }, []);
+  }, [addItem]);
 
   const applyTheme = useCallback(
     (themeName: string | undefined) => {

packages/cli/src/ui/themes/no-color.ts

@@ -0,0 +1,91 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { Theme, ColorsTheme } from './theme.js';
+
+const noColorColorsTheme: ColorsTheme = {
+  type: 'ansi',
+  Background: '',
+  Foreground: '',
+  LightBlue: '',
+  AccentBlue: '',
+  AccentPurple: '',
+  AccentCyan: '',
+  AccentGreen: '',
+  AccentYellow: '',
+  AccentRed: '',
+  SubtleComment: '',
+  Gray: '',
+};
+
+export const NoColorTheme: Theme = new Theme(
+  'No Color',
+  'dark',
+  {
+    hljs: {
+      display: 'block',
+      overflowX: 'auto',
+      padding: '0.5em',
+    },
+    'hljs-keyword': {},
+    'hljs-literal': {},
+    'hljs-symbol': {},
+    'hljs-name': {},
+    'hljs-link': {
+      textDecoration: 'underline',
+    },
+    'hljs-built_in': {},
+    'hljs-type': {},
+    'hljs-number': {},
+    'hljs-class': {},
+    'hljs-string': {},
+    'hljs-meta-string': {},
+    'hljs-regexp': {},
+    'hljs-template-tag': {},
+    'hljs-subst': {},
+    'hljs-function': {},
+    'hljs-title': {},
+    'hljs-params': {},
+    'hljs-formula': {},
+    'hljs-comment': {
+      fontStyle: 'italic',
+    },
+    'hljs-quote': {
+      fontStyle: 'italic',
+    },
+    'hljs-doctag': {},
+    'hljs-meta': {},
+    'hljs-meta-keyword': {},
+    'hljs-tag': {},
+    'hljs-variable': {},
+    'hljs-template-variable': {},
+    'hljs-attr': {},
+    'hljs-attribute': {},
+    'hljs-builtin-name': {},
+    'hljs-section': {},
+    'hljs-emphasis': {
+      fontStyle: 'italic',
+    },
+    'hljs-strong': {
+      fontWeight: 'bold',
+    },
+    'hljs-bullet': {},
+    'hljs-selector-tag': {},
+    'hljs-selector-id': {},
+    'hljs-selector-class': {},
+    'hljs-selector-attr': {},
+    'hljs-selector-pseudo': {},
+    'hljs-addition': {
+      display: 'inline-block',
+      width: '100%',
+    },
+    'hljs-deletion': {
+      display: 'inline-block',
+      width: '100%',
+    },
+  },
+  noColorColorsTheme,
+);

packages/cli/src/ui/themes/theme-manager.ts

@@ -17,6 +17,8 @@ import { XCode } from './xcode.js';
 import { Theme, ThemeType } from './theme.js';
 import { ANSI } from './ansi.js';
 import { ANSILight } from './ansi-light.js';
+import { NoColorTheme } from './no-color.js';
+import process from 'node:process';
 
 export interface ThemeDisplay {
   name: string;
@@ -110,6 +112,9 @@ class ThemeManager {
    * Returns the currently active theme object.
    */
   getActiveTheme(): Theme {
+    if (process.env.NO_COLOR) {
+      return NoColorTheme;
+    }
     return this.activeTheme;
   }
 }