Log server information on error.

- The goal of this is to enable us to better diagnose server issues when they occur.
- Added tests because why not.

packages/server/src/utils/errorReporting.test.ts

@@ -0,0 +1,220 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, vi, beforeEach, afterEach, Mock } from 'vitest';
+
+// Use a type alias for SpyInstance as it's not directly exported
+type SpyInstance = ReturnType<typeof vi.spyOn>;
+import { reportError } from './errorReporting.js';
+import fs from 'node:fs/promises';
+import os from 'node:os';
+
+// Mock dependencies
+vi.mock('node:fs/promises');
+vi.mock('node:os');
+
+describe('reportError', () => {
+  let consoleErrorSpy: SpyInstance;
+  const MOCK_TMP_DIR = '/tmp';
+  const MOCK_TIMESTAMP = '2025-01-01T00-00-00-000Z';
+
+  beforeEach(() => {
+    vi.resetAllMocks();
+    consoleErrorSpy = vi.spyOn(console, 'error').mockImplementation(() => {});
+    (os.tmpdir as Mock).mockReturnValue(MOCK_TMP_DIR);
+    vi.spyOn(Date.prototype, 'toISOString').mockReturnValue(MOCK_TIMESTAMP);
+  });
+
+  afterEach(() => {
+    consoleErrorSpy.mockRestore();
+    vi.restoreAllMocks();
+  });
+
+  const getExpectedReportPath = (type: string) =>
+    `${MOCK_TMP_DIR}/gemini-client-error-${type}-${MOCK_TIMESTAMP}.json`;
+
+  it('should generate a report and log the path', async () => {
+    const error = new Error('Test error');
+    error.stack = 'Test stack';
+    const baseMessage = 'An error occurred.';
+    const context = { data: 'test context' };
+    const type = 'test-type';
+    const expectedReportPath = getExpectedReportPath(type);
+
+    (fs.writeFile as Mock).mockResolvedValue(undefined);
+
+    await reportError(error, baseMessage, context, type);
+
+    expect(os.tmpdir).toHaveBeenCalledTimes(1);
+    expect(fs.writeFile).toHaveBeenCalledWith(
+      expectedReportPath,
+      JSON.stringify(
+        {
+          error: { message: 'Test error', stack: error.stack },
+          context,
+        },
+        null,
+        2,
+      ),
+    );
+    expect(consoleErrorSpy).toHaveBeenCalledWith(
+      `${baseMessage} Full report available at: ${expectedReportPath}`,
+    );
+  });
+
+  it('should handle errors that are plain objects with a message property', async () => {
+    const error = { message: 'Test plain object error' };
+    const baseMessage = 'Another error.';
+    const type = 'general';
+    const expectedReportPath = getExpectedReportPath(type);
+
+    (fs.writeFile as Mock).mockResolvedValue(undefined);
+    await reportError(error, baseMessage);
+
+    expect(fs.writeFile).toHaveBeenCalledWith(
+      expectedReportPath,
+      JSON.stringify(
+        {
+          error: { message: 'Test plain object error' },
+        },
+        null,
+        2,
+      ),
+    );
+    expect(consoleErrorSpy).toHaveBeenCalledWith(
+      `${baseMessage} Full report available at: ${expectedReportPath}`,
+    );
+  });
+
+  it('should handle string errors', async () => {
+    const error = 'Just a string error';
+    const baseMessage = 'String error occurred.';
+    const type = 'general';
+    const expectedReportPath = getExpectedReportPath(type);
+
+    (fs.writeFile as Mock).mockResolvedValue(undefined);
+    await reportError(error, baseMessage);
+
+    expect(fs.writeFile).toHaveBeenCalledWith(
+      expectedReportPath,
+      JSON.stringify(
+        {
+          error: { message: 'Just a string error' },
+        },
+        null,
+        2,
+      ),
+    );
+    expect(consoleErrorSpy).toHaveBeenCalledWith(
+      `${baseMessage} Full report available at: ${expectedReportPath}`,
+    );
+  });
+
+  it('should log fallback message if writing report fails', async () => {
+    const error = new Error('Main error');
+    const baseMessage = 'Failed operation.';
+    const writeError = new Error('Failed to write file');
+    const context = ['some context'];
+    const type = 'general';
+    const expectedReportPath = getExpectedReportPath(type);
+
+    (fs.writeFile as Mock).mockRejectedValue(writeError);
+
+    await reportError(error, baseMessage, context, type);
+
+    expect(fs.writeFile).toHaveBeenCalledWith(
+      expectedReportPath,
+      expect.any(String),
+    ); // It still tries to write
+    expect(consoleErrorSpy).toHaveBeenCalledWith(
+      `${baseMessage} Additionally, failed to write detailed error report:`,
+      writeError,
+    );
+    expect(consoleErrorSpy).toHaveBeenCalledWith(
+      'Original error that triggered report generation:',
+      error,
+    );
+    expect(consoleErrorSpy).toHaveBeenCalledWith('Original context:', context);
+  });
+
+  it('should handle stringification failure of report content (e.g. BigInt in context)', async () => {
+    const error = new Error('Main error');
+    error.stack = 'Main stack';
+    const baseMessage = 'Failed operation with BigInt.';
+    const context = { a: BigInt(1) }; // BigInt cannot be stringified by JSON.stringify
+    const type = 'bigint-fail';
+    const stringifyError = new TypeError(
+      'Do not know how to serialize a BigInt',
+    );
+    const expectedMinimalReportPath = getExpectedReportPath(type);
+
+    // Simulate JSON.stringify throwing an error for the full report
+    const originalJsonStringify = JSON.stringify;
+    let callCount = 0;
+    vi.spyOn(JSON, 'stringify').mockImplementation((value, replacer, space) => {
+      callCount++;
+      if (callCount === 1) {
+        // First call is for the full report content
+        throw stringifyError;
+      }
+      // Subsequent calls (for minimal report) should succeed
+      return originalJsonStringify(value, replacer, space);
+    });
+
+    (fs.writeFile as Mock).mockResolvedValue(undefined); // Mock for the minimal report write
+
+    await reportError(error, baseMessage, context, type);
+
+    expect(consoleErrorSpy).toHaveBeenCalledWith(
+      `${baseMessage} Could not stringify report content (likely due to context):`,
+      stringifyError,
+    );
+    expect(consoleErrorSpy).toHaveBeenCalledWith(
+      'Original error that triggered report generation:',
+      error,
+    );
+    expect(consoleErrorSpy).toHaveBeenCalledWith(
+      'Original context could not be stringified or included in report.',
+    );
+    // Check that it attempts to write a minimal report
+    expect(fs.writeFile).toHaveBeenCalledWith(
+      expectedMinimalReportPath,
+      originalJsonStringify(
+        { error: { message: error.message, stack: error.stack } },
+        null,
+        2,
+      ),
+    );
+    expect(consoleErrorSpy).toHaveBeenCalledWith(
+      `${baseMessage} Partial report (excluding context) available at: ${expectedMinimalReportPath}`,
+    );
+  });
+
+  it('should generate a report without context if context is not provided', async () => {
+    const error = new Error('Error without context');
+    error.stack = 'No context stack';
+    const baseMessage = 'Simple error.';
+    const type = 'general';
+    const expectedReportPath = getExpectedReportPath(type);
+
+    (fs.writeFile as Mock).mockResolvedValue(undefined);
+    await reportError(error, baseMessage, undefined, type);
+
+    expect(fs.writeFile).toHaveBeenCalledWith(
+      expectedReportPath,
+      JSON.stringify(
+        {
+          error: { message: 'Error without context', stack: error.stack },
+        },
+        null,
+        2,
+      ),
+    );
+    expect(consoleErrorSpy).toHaveBeenCalledWith(
+      `${baseMessage} Full report available at: ${expectedReportPath}`,
+    );
+  });
+});