Add extension linking capabilities in cli (#16040)

packages/cli/src/ui/commands/extensionsCommand.test.ts

@@ -31,6 +31,7 @@ import {
   inferInstallMetadata,
 } from '../../config/extension-manager.js';
 import { SettingScope } from '../../config/settings.js';
+import { stat } from 'node:fs/promises';
 
 vi.mock('../../config/extension-manager.js', async (importOriginal) => {
   const actual =
@@ -42,11 +43,16 @@ vi.mock('../../config/extension-manager.js', async (importOriginal) => {
 });
 
 import open from 'open';
+import type { Stats } from 'node:fs';
 
 vi.mock('open', () => ({
   default: vi.fn(),
 }));
 
+vi.mock('node:fs/promises', () => ({
+  stat: vi.fn(),
+}));
+
 vi.mock('../../config/extensions/update.js', () => ({
   updateExtension: vi.fn(),
   checkForAllExtensionUpdates: vi.fn(),
@@ -493,34 +499,37 @@ describe('extensionsCommand', () => {
   });
 
   describe('when enableExtensionReloading is true', () => {
-    it('should include enable, disable, install, and uninstall subcommands', () => {
+    it('should include enable, disable, install, link, and uninstall subcommands', () => {
       const command = extensionsCommand(true);
       const subCommandNames = command.subCommands?.map((cmd) => cmd.name);
       expect(subCommandNames).toContain('enable');
       expect(subCommandNames).toContain('disable');
       expect(subCommandNames).toContain('install');
+      expect(subCommandNames).toContain('link');
       expect(subCommandNames).toContain('uninstall');
     });
   });
 
   describe('when enableExtensionReloading is false', () => {
-    it('should not include enable, disable, install, and uninstall subcommands', () => {
+    it('should not include enable, disable, install, link, and uninstall subcommands', () => {
       const command = extensionsCommand(false);
       const subCommandNames = command.subCommands?.map((cmd) => cmd.name);
       expect(subCommandNames).not.toContain('enable');
       expect(subCommandNames).not.toContain('disable');
       expect(subCommandNames).not.toContain('install');
+      expect(subCommandNames).not.toContain('link');
       expect(subCommandNames).not.toContain('uninstall');
     });
   });
 
   describe('when enableExtensionReloading is not provided', () => {
-    it('should not include enable, disable, install, and uninstall subcommands by default', () => {
+    it('should not include enable, disable, install, link, and uninstall subcommands by default', () => {
       const command = extensionsCommand();
       const subCommandNames = command.subCommands?.map((cmd) => cmd.name);
       expect(subCommandNames).not.toContain('enable');
       expect(subCommandNames).not.toContain('disable');
       expect(subCommandNames).not.toContain('install');
+      expect(subCommandNames).not.toContain('link');
       expect(subCommandNames).not.toContain('uninstall');
     });
   });
@@ -617,6 +626,88 @@ describe('extensionsCommand', () => {
     });
   });
 
+  describe('link', () => {
+    let linkAction: SlashCommand['action'];
+
+    beforeEach(() => {
+      linkAction = extensionsCommand(true).subCommands?.find(
+        (cmd) => cmd.name === 'link',
+      )?.action;
+
+      expect(linkAction).not.toBeNull();
+      mockContext.invocation!.name = 'link';
+    });
+
+    it('should show usage if no extension is provided', async () => {
+      await linkAction!(mockContext, '');
+      expect(mockContext.ui.addItem).toHaveBeenCalledWith(
+        {
+          type: MessageType.ERROR,
+          text: 'Usage: /extensions link <source>',
+        },
+        expect.any(Number),
+      );
+      expect(mockInstallExtension).not.toHaveBeenCalled();
+    });
+
+    it('should call installExtension and show success message', async () => {
+      const packageName = 'test-extension-package';
+      mockInstallExtension.mockResolvedValue({ name: packageName });
+      vi.mocked(stat).mockResolvedValue({
+        size: 100,
+      } as Stats);
+      await linkAction!(mockContext, packageName);
+      expect(mockInstallExtension).toHaveBeenCalledWith({
+        source: packageName,
+        type: 'link',
+      });
+      expect(mockContext.ui.addItem).toHaveBeenCalledWith(
+        {
+          type: MessageType.INFO,
+          text: `Linking extension from "${packageName}"...`,
+        },
+        expect.any(Number),
+      );
+      expect(mockContext.ui.addItem).toHaveBeenCalledWith(
+        {
+          type: MessageType.INFO,
+          text: `Extension "${packageName}" linked successfully.`,
+        },
+        expect.any(Number),
+      );
+    });
+
+    it('should show error message on linking failure', async () => {
+      const packageName = 'test-extension-package';
+      const errorMessage = 'link failed';
+      mockInstallExtension.mockRejectedValue(new Error(errorMessage));
+      vi.mocked(stat).mockResolvedValue({
+        size: 100,
+      } as Stats);
+
+      await linkAction!(mockContext, packageName);
+      expect(mockInstallExtension).toHaveBeenCalledWith({
+        source: packageName,
+        type: 'link',
+      });
+      expect(mockContext.ui.addItem).toHaveBeenCalledWith(
+        {
+          type: MessageType.ERROR,
+          text: `Failed to link extension from "${packageName}": ${errorMessage}`,
+        },
+        expect.any(Number),
+      );
+    });
+
+    it('should show error message for invalid source', async () => {
+      const packageName = 'test-extension-package';
+      const errorMessage = 'invalid path';
+      vi.mocked(stat).mockRejectedValue(new Error(errorMessage));
+      await linkAction!(mockContext, packageName);
+      expect(mockInstallExtension).not.toHaveBeenCalled();
+    });
+  });
+
   describe('uninstall', () => {
     let uninstallAction: SlashCommand['action'];
 

packages/cli/src/ui/commands/extensionsCommand.ts

@@ -4,7 +4,11 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import { debugLogger, listExtensions } from '@google/gemini-cli-core';
+import {
+  debugLogger,
+  listExtensions,
+  type ExtensionInstallMetadata,
+} from '@google/gemini-cli-core';
 import type { ExtensionUpdateInfo } from '../../config/extension.js';
 import { getErrorMessage } from '../../utils/errors.js';
 import {
@@ -26,6 +30,7 @@ import {
 } from '../../config/extension-manager.js';
 import { SettingScope } from '../../config/settings.js';
 import { theme } from '../semantic-colors.js';
+import { stat } from 'node:fs/promises';
 
 function showMessageIfNoExtensions(
   context: CommandContext,
@@ -510,6 +515,88 @@ async function installAction(context: CommandContext, args: string) {
   }
 }
 
+async function linkAction(context: CommandContext, args: string) {
+  const extensionLoader = context.services.config?.getExtensionLoader();
+  if (!(extensionLoader instanceof ExtensionManager)) {
+    debugLogger.error(
+      `Cannot ${context.invocation?.name} extensions in this environment`,
+    );
+    return;
+  }
+
+  const sourceFilepath = args.trim();
+  if (!sourceFilepath) {
+    context.ui.addItem(
+      {
+        type: MessageType.ERROR,
+        text: `Usage: /extensions link <source>`,
+      },
+      Date.now(),
+    );
+    return;
+  }
+  if (/[;&|`'"]/.test(sourceFilepath)) {
+    context.ui.addItem(
+      {
+        type: MessageType.ERROR,
+        text: `Source file path contains disallowed characters: ${sourceFilepath}`,
+      },
+      Date.now(),
+    );
+    return;
+  }
+
+  try {
+    await stat(sourceFilepath);
+  } catch (error) {
+    context.ui.addItem(
+      {
+        type: MessageType.ERROR,
+        text: `Invalid source: ${sourceFilepath}`,
+      },
+      Date.now(),
+    );
+    debugLogger.error(
+      `Failed to stat path "${sourceFilepath}": ${getErrorMessage(error)}`,
+    );
+    return;
+  }
+
+  context.ui.addItem(
+    {
+      type: MessageType.INFO,
+      text: `Linking extension from "${sourceFilepath}"...`,
+    },
+    Date.now(),
+  );
+
+  try {
+    const installMetadata: ExtensionInstallMetadata = {
+      source: sourceFilepath,
+      type: 'link',
+    };
+    const extension =
+      await extensionLoader.installOrUpdateExtension(installMetadata);
+    context.ui.addItem(
+      {
+        type: MessageType.INFO,
+        text: `Extension "${extension.name}" linked successfully.`,
+      },
+      Date.now(),
+    );
+  } catch (error) {
+    context.ui.addItem(
+      {
+        type: MessageType.ERROR,
+        text: `Failed to link extension from "${sourceFilepath}": ${getErrorMessage(
+          error,
+        )}`,
+      },
+      Date.now(),
+    );
+  }
+}
+
 async function uninstallAction(context: CommandContext, args: string) {
   const extensionLoader = context.services.config?.getExtensionLoader();
   if (!(extensionLoader instanceof ExtensionManager)) {
@@ -645,6 +732,14 @@ const installCommand: SlashCommand = {
   action: installAction,
 };
 
+const linkCommand: SlashCommand = {
+  name: 'link',
+  description: 'Link an extension from a local path',
+  kind: CommandKind.BUILT_IN,
+  autoExecute: false,
+  action: linkAction,
+};
+
 const uninstallCommand: SlashCommand = {
   name: 'uninstall',
   description: 'Uninstall an extension',
@@ -675,7 +770,13 @@ export function extensionsCommand(
   enableExtensionReloading?: boolean,
 ): SlashCommand {
   const conditionalCommands = enableExtensionReloading
-    ? [disableCommand, enableCommand, installCommand, uninstallCommand]
+    ? [
+        disableCommand,
+        enableCommand,
+        installCommand,
+        uninstallCommand,
+        linkCommand,
+      ]
     : [];
   return {
     name: 'extensions',