fix(browser): Check for existence of instrumentation targets (#8939)

There are cases when global objects such as the window object are
shimmed that they define properties such as `document`, but the actual
value is undefined. This exact situation has been occurring and is
causing the instrumentDOM function to throw an error as `'document' in
WINDOW` is technically true though the value is falsey. We should rather
attempt an actual check of the value being truthy rather than if the
property is defined

Co-authored-by: Luca Forstner <[email protected]>

Author: SorsOps

packages/utils/src/instrument.ts

@@ -247,8 +247,9 @@ export function parseFetchArgs(fetchArgs: unknown[]): { method: string; url: str
 }
 
 /** JSDoc */
-function instrumentXHR(): void {
-  if (!('XMLHttpRequest' in WINDOW)) {
+export function instrumentXHR(): void {
+  // eslint-disable-next-line @typescript-eslint/no-unsafe-member-access
+  if (!(WINDOW as any).XMLHttpRequest) {
     return;
   }
 
@@ -539,8 +540,8 @@ type InstrumentedElement = Element & {
 };
 
 /** JSDoc */
-function instrumentDOM(): void {
-  if (!('document' in WINDOW)) {
+export function instrumentDOM(): void {
+  if (!WINDOW.document) {
     return;
   }
 

packages/utils/test/instrument.test.ts

@@ -1,6 +1,22 @@
-import { parseFetchArgs } from '../src/instrument';
+import { instrumentDOM, instrumentXHR, parseFetchArgs } from '../src/instrument';
+
+jest.mock('../src/worldwide', () => ({
+  // Return an empty object with undefined properties
+  getGlobalObject: () => ({
+    document: undefined,
+    XMLHttpRequest: undefined,
+  }),
+}));
 
 describe('instrument', () => {
+  it('instrumentXHR() does not throw if XMLHttpRequest is a key on window but not defined', () => {
+    expect(instrumentXHR).not.toThrow();
+  });
+
+  it('instrumentDOM() does not throw if XMLHttpRequest is a key on window but not defined', () => {
+    expect(instrumentDOM).not.toThrow();
+  });
+
   describe('parseFetchArgs', () => {
     it.each([
       ['string URL only', ['http://example.com'], { method: 'GET', url: 'http://example.com' }],