fix(plugin-fetch): check if PerformanceObserver exists

packages/opentelemetry-plugin-fetch/src/fetch.ts

@@ -174,6 +174,9 @@ export class FetchPlugin extends core.BasePlugin<Promise<Response>> {
   ): void {
     let resources: PerformanceResourceTiming[] = resourcesObserver.entries;
     if (!resources.length) {
+      if (!performance.getEntriesByType) {
+        return;
+      }
       // fallback - either Observer is not available or it took longer
       // then OBSERVER_WAIT_TIME_MS and observer didn't collect enough
       // information
@@ -225,7 +228,9 @@ export class FetchPlugin extends core.BasePlugin<Promise<Response>> {
     response: FetchResponse
   ) {
     const endTime = core.hrTime();
-    spanData.observer.disconnect();
+    if (spanData.observer) {
+      spanData.observer.disconnect();
+    }
     this._addFinalSpanAttributes(span, response);
 
     setTimeout(() => {
@@ -323,6 +328,11 @@ export class FetchPlugin extends core.BasePlugin<Promise<Response>> {
   private _prepareSpanData(spanUrl: string): SpanData {
     const startTime = core.hrTime();
     const entries: PerformanceResourceTiming[] = [];
+
+    if (typeof window.PerformanceObserver === 'undefined') {
+      return { entries, startTime, spanUrl };
+    }
+
     const observer: PerformanceObserver = new PerformanceObserver(list => {
       const entries = list.getEntries() as PerformanceResourceTiming[];
       entries.forEach(entry => {

packages/opentelemetry-plugin-fetch/src/types.ts

@@ -39,7 +39,7 @@ export interface FetchError {
  */
 export interface SpanData {
   entries: PerformanceResourceTiming[];
-  observer: PerformanceObserver;
+  observer?: PerformanceObserver;
   spanUrl: string;
   startTime: api.HrTime;
 }

packages/opentelemetry-plugin-fetch/test/fetch.test.ts

@@ -583,4 +583,22 @@ describe('fetch', () => {
       );
     });
   });
+
+  describe('when PerformanceObserver is undefined', () => {
+    beforeEach(done => {
+      Object.defineProperty(window, 'PerformanceObserver', {
+        value: undefined,
+      });
+
+      prepareData(done, url, {});
+    });
+
+    afterEach(() => {
+      clearData();
+    });
+
+    it('should still create spans', () => {
+      assert.strictEqual(exportSpy.args.length, 2, 'no spans created');
+    });
+  });
 });