Fix circular reference JSON serialization in telemetry logging (#4150)

1 files changed, 73 insertions, 0 deletions

diff --git a/packages/core/src/utils/safeJsonStringify.test.ts b/packages/core/src/utils/safeJsonStringify.test.ts
new file mode 100644
index 00000000..9a38c048
--- /dev/null
+++ b/packages/core/src/utils/safeJsonStringify.test.ts
@@ -0,0 +1,73 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect } from 'vitest';
+import { safeJsonStringify } from './safeJsonStringify.js';
+
+describe('safeJsonStringify', () => {
+  it('should stringify normal objects without issues', () => {
+    const obj = { name: 'test', value: 42 };
+    const result = safeJsonStringify(obj);
+    expect(result).toBe('{"name":"test","value":42}');
+  });
+
+  it('should handle circular references by replacing them with [Circular]', () => {
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    const obj: any = { name: 'test' };
+    obj.circular = obj; // Create circular reference
+
+    const result = safeJsonStringify(obj);
+    expect(result).toBe('{"name":"test","circular":"[Circular]"}');
+  });
+
+  it('should handle complex circular structures like HttpsProxyAgent', () => {
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    const agent: any = {
+      sockets: {},
+      options: { host: 'example.com' },
+    };
+    agent.sockets['example.com'] = [{ agent }];
+
+    const result = safeJsonStringify(agent);
+    expect(result).toContain('[Circular]');
+    expect(result).toContain('example.com');
+  });
+
+  it('should respect the space parameter for formatting', () => {
+    const obj = { name: 'test', value: 42 };
+    const result = safeJsonStringify(obj, 2);
+    expect(result).toBe('{\n  "name": "test",\n  "value": 42\n}');
+  });
+
+  it('should handle circular references with formatting', () => {
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    const obj: any = { name: 'test' };
+    obj.circular = obj;
+
+    const result = safeJsonStringify(obj, 2);
+    expect(result).toBe('{\n  "name": "test",\n  "circular": "[Circular]"\n}');
+  });
+
+  it('should handle arrays with circular references', () => {
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    const arr: any[] = [{ id: 1 }];
+    arr[0].parent = arr; // Create circular reference
+
+    const result = safeJsonStringify(arr);
+    expect(result).toBe('[{"id":1,"parent":"[Circular]"}]');
+  });
+
+  it('should handle null and undefined values', () => {
+    expect(safeJsonStringify(null)).toBe('null');
+    expect(safeJsonStringify(undefined)).toBe(undefined);
+  });
+
+  it('should handle primitive values', () => {
+    expect(safeJsonStringify('test')).toBe('"test"');
+    expect(safeJsonStringify(42)).toBe('42');
+    expect(safeJsonStringify(true)).toBe('true');
+  });
+});