Improve auth env var validation logic and messaging to detect settings that confuse GenAI SDK (#1381)

Co-authored-by: Scott Densmore <scottdensmore@mac.com>
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

packages/core/src/code_assist/setup.test.ts

@@ -0,0 +1,82 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { setupUser, ProjectIdRequiredError } from './setup.js';
+import { CodeAssistServer } from '../code_assist/server.js';
+import { OAuth2Client } from 'google-auth-library';
+import { GeminiUserTier, UserTierId } from './types.js';
+
+vi.mock('../code_assist/server.js');
+
+const mockPaidTier: GeminiUserTier = {
+  id: UserTierId.STANDARD,
+  name: 'paid',
+  description: 'Paid tier',
+};
+
+describe('setupUser', () => {
+  let mockLoad: ReturnType<typeof vi.fn>;
+  let mockOnboardUser: ReturnType<typeof vi.fn>;
+
+  beforeEach(() => {
+    vi.resetAllMocks();
+    mockLoad = vi.fn();
+    mockOnboardUser = vi.fn().mockResolvedValue({
+      done: true,
+      response: {
+        cloudaicompanionProject: {
+          id: 'server-project',
+        },
+      },
+    });
+    vi.mocked(CodeAssistServer).mockImplementation(
+      () =>
+        ({
+          loadCodeAssist: mockLoad,
+          onboardUser: mockOnboardUser,
+        }) as unknown as CodeAssistServer,
+    );
+  });
+
+  it('should use GOOGLE_CLOUD_PROJECT when set', async () => {
+    process.env.GOOGLE_CLOUD_PROJECT = 'test-project';
+    mockLoad.mockResolvedValue({
+      currentTier: mockPaidTier,
+    });
+    await setupUser({} as OAuth2Client);
+    expect(CodeAssistServer).toHaveBeenCalledWith(
+      expect.any(Object),
+      'test-project',
+    );
+  });
+
+  it('should treat empty GOOGLE_CLOUD_PROJECT as undefined and use project from server', async () => {
+    process.env.GOOGLE_CLOUD_PROJECT = '';
+    mockLoad.mockResolvedValue({
+      cloudaicompanionProject: 'server-project',
+      currentTier: mockPaidTier,
+    });
+    const projectId = await setupUser({} as OAuth2Client);
+    expect(CodeAssistServer).toHaveBeenCalledWith(
+      expect.any(Object),
+      undefined,
+    );
+    expect(projectId).toBe('server-project');
+  });
+
+  it('should throw ProjectIdRequiredError when no project ID is available', async () => {
+    delete process.env.GOOGLE_CLOUD_PROJECT;
+    // And the server itself requires a project ID internally
+    vi.mocked(CodeAssistServer).mockImplementation(() => {
+      throw new ProjectIdRequiredError();
+    });
+
+    await expect(setupUser({} as OAuth2Client)).rejects.toThrow(
+      ProjectIdRequiredError,
+    );
+  });
+});

packages/core/src/code_assist/setup.ts

@@ -28,7 +28,7 @@ export class ProjectIdRequiredError extends Error {
  * @returns the user's actual project id
  */
 export async function setupUser(client: OAuth2Client): Promise<string> {
-  let projectId = process.env.GOOGLE_CLOUD_PROJECT;
+  let projectId = process.env.GOOGLE_CLOUD_PROJECT || undefined;
   const caServer = new CodeAssistServer(client, projectId);
 
   const clientMetadata: ClientMetadata = {