fix(hub): Don't set lastEventID for transactions (#3966)

As lastEventID is often just used for UserFeedback, let's not set it when we capture transactions. This is technically a breaking change in terms of behaviour, but we elect to not put this in a major as the previous behaviour was incorrect.

Validated with unit tests.

Co-authored-by: Kamil Ogórek <kamil.ogorek@gmail.com>

packages/hub/src/hub.ts

@@ -248,7 +248,11 @@ export class Hub implements HubInterface {
    * @inheritDoc
    */
   public captureEvent(event: Event, hint?: EventHint): string {
-    const eventId = (this._lastEventId = uuid4());
+    const eventId = uuid4();
+    if (event.type !== 'transaction') {
+      this._lastEventId = eventId;
+    }
+
     this._invokeClient('captureEvent', event, {
       ...hint,
       event_id: eventId,

packages/hub/test/hub.test.ts

@@ -279,6 +279,29 @@ describe('Hub', () => {
       // @ts-ignore Says mock object is type unknown
       expect(spy.mock.calls[0][2].event_id).toBeTruthy();
     });
+
+    test('sets lastEventId', () => {
+      const event: Event = {
+        extra: { b: 3 },
+      };
+      const hub = new Hub();
+      const spy = jest.spyOn(hub as any, '_invokeClient');
+      hub.captureEvent(event);
+      // @ts-ignore Says mock object is type unknown
+      expect(spy.mock.calls[0][2].event_id).toEqual(hub.lastEventId());
+    });
+
+    test('transactions do not set lastEventId', () => {
+      const event: Event = {
+        extra: { b: 3 },
+        type: 'transaction',
+      };
+      const hub = new Hub();
+      const spy = jest.spyOn(hub as any, '_invokeClient');
+      hub.captureEvent(event);
+      // @ts-ignore Says mock object is type unknown
+      expect(spy.mock.calls[0][2].event_id).not.toEqual(hub.lastEventId());
+    });
   });
 
   test('lastEventId should be the same as last created', () => {