feat(cli): improve API error parsing and display (#829)

packages/cli/src/ui/utils/errorParsing.test.ts

@@ -0,0 +1,56 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect } from 'vitest';
+import { parseAndFormatApiError } from './errorParsing.js';
+
+describe('parseAndFormatApiError', () => {
+  it('should format a valid API error JSON', () => {
+    const errorMessage =
+      'got status: 400 Bad Request. {"error":{"code":400,"message":"API key not valid. Please pass a valid API key.","status":"INVALID_ARGUMENT"}}';
+    const expected =
+      'API Error: API key not valid. Please pass a valid API key. (Status: INVALID_ARGUMENT)';
+    expect(parseAndFormatApiError(errorMessage)).toBe(expected);
+  });
+
+  it('should return the original message if it is not a JSON error', () => {
+    const errorMessage = 'This is a plain old error message';
+    expect(parseAndFormatApiError(errorMessage)).toBe(errorMessage);
+  });
+
+  it('should return the original message for malformed JSON', () => {
+    const errorMessage = '[Stream Error: {"error": "malformed}';
+    expect(parseAndFormatApiError(errorMessage)).toBe(errorMessage);
+  });
+
+  it('should handle JSON that does not match the ApiError structure', () => {
+    const errorMessage = '[Stream Error: {"not_an_error": "some other json"}]';
+    expect(parseAndFormatApiError(errorMessage)).toBe(errorMessage);
+  });
+
+  it('should format a nested API error', () => {
+    const nestedErrorMessage = JSON.stringify({
+      error: {
+        code: 429,
+        message:
+          "Gemini 2.5 Pro Preview doesn't have a free quota tier. For more information on this error, head to: https://ai.google.dev/gemini-api/docs/rate-limits.",
+        status: 'RESOURCE_EXHAUSTED',
+      },
+    });
+
+    const errorMessage = JSON.stringify({
+      error: {
+        code: 429,
+        message: nestedErrorMessage,
+        status: 'Too Many Requests',
+      },
+    });
+
+    expect(parseAndFormatApiError(errorMessage)).toBe(
+      "API Error: Gemini 2.5 Pro Preview doesn't have a free quota tier. For more information on this error, head to: https://ai.google.dev/gemini-api/docs/rate-limits. (Status: Too Many Requests)",
+    );
+  });
+});