fix: fix based on comment

packages/analytics-browser/src/browser-client.ts

@@ -10,6 +10,7 @@ import {
   isFormInteractionTrackingEnabled,
   setConnectorDeviceId,
   setConnectorUserId,
+  isNewSession,
 } from '@amplitude/analytics-client-common';
 import {
   BrowserClient,
@@ -250,14 +251,13 @@ export class AmplitudeBrowser extends AmplitudeCore implements BrowserClient {
 
   async process(event: Event) {
     const currentTime = Date.now();
-    const lastEventTime = this.config.lastEventTime || Date.now();
-    const timeSinceLastEvent = currentTime - lastEventTime;
+    const _isNewSession = isNewSession(this.config.sessionTimeout, this.config.lastEventTime);
 
     if (
       event.event_type !== DEFAULT_SESSION_START_EVENT &&
       event.event_type !== DEFAULT_SESSION_END_EVENT &&
       (!event.session_id || event.session_id === this.getSessionId()) &&
-      timeSinceLastEvent > this.config.sessionTimeout
+      _isNewSession
     ) {
       this.setSessionId(currentTime);
     }

packages/analytics-client-common/src/index.ts

@@ -1,6 +1,7 @@
 export { CampaignParser } from './attribution/campaign-parser';
 export { CampaignTracker } from './attribution/campaign-tracker';
 export { getQueryParams } from './query-params';
+export { isNewSession } from './session';
 export { getCookieName, getOldCookieName } from './cookie-name';
 export { CookieStorage } from './storage/cookie';
 export { FetchTransport } from './transports/fetch';

packages/analytics-client-common/src/session.ts

@@ -0,0 +1,7 @@
+export const isNewSession = (sessionTimeout: number, lastEventTime?: number): boolean => {
+  const _currentTime = Date.now();
+  const _lastEventTime = lastEventTime || Date.now();
+  const timeSinceLastEvent = _currentTime - _lastEventTime;
+
+  return timeSinceLastEvent > sessionTimeout;
+};

packages/analytics-client-common/test/session.test.ts

@@ -0,0 +1,25 @@
+import { isNewSession } from '../src/session';
+
+describe('session', () => {
+  const sessionTimeout: number = 30 * 60 * 1000;
+
+  test('should be a new session for the first event', () => {
+    const _isNewSession = isNewSession(sessionTimeout, undefined);
+
+    expect(_isNewSession).toBe(false);
+  });
+
+  test('should be a new session', () => {
+    const lastEventTime = Date.now() - sessionTimeout * 2;
+    const _isNewSession = isNewSession(sessionTimeout, lastEventTime);
+
+    expect(_isNewSession).toBe(true);
+  });
+
+  test('should be in a same session', () => {
+    const lastEventTime = Date.now();
+    const _isNewSession = isNewSession(sessionTimeout, lastEventTime);
+
+    expect(_isNewSession).toBe(false);
+  });
+});

packages/plugin-web-attribution-browser/src/helpers.ts

@@ -31,8 +31,7 @@ export const isNewCampaign = (
   }
 
   //In the same session, no referrer should not override or unset any persisting query params
-  const isNoReferrer = !referring_domain;
-  if (isNewSession && isNoReferrer) {
+  if (isNewSession && !referring_domain) {
     return false;
   }
 

packages/plugin-web-attribution-browser/src/web-attribution.ts

@@ -2,6 +2,7 @@ import { CampaignParser } from '@amplitude/analytics-client-common';
 import { BeforePlugin, BrowserClient, BrowserConfig, Campaign, Event, Storage } from '@amplitude/analytics-types';
 import { createCampaignEvent, getDefaultExcludedReferrers, getStorageKey, isNewCampaign } from './helpers';
 import { CreateWebAttributionPlugin, Options } from './typings/web-attribution';
+import { isNewSession } from '@amplitude/analytics-client-common';
 
 export const webAttributionPlugin: CreateWebAttributionPlugin = function (options: Options = {}) {
   const plugin: BeforePlugin = {
@@ -26,13 +27,9 @@ export const webAttributionPlugin: CreateWebAttributionPlugin = function (option
         storage.get(storageKey),
       ]);
 
-      const currentTime = Date.now();
-      const lastEventTime = config.lastEventTime || Date.now();
-      const timeSinceLastEvent = currentTime - lastEventTime;
+      const _isNewSession = isNewSession(config.sessionTimeout, config.lastEventTime);
 
-      const isNewSession = timeSinceLastEvent > config.sessionTimeout;
-
-      if (isNewCampaign(currentCampaign, previousCampaign, pluginConfig, isNewSession)) {
+      if (isNewCampaign(currentCampaign, previousCampaign, pluginConfig, _isNewSession)) {
         if (pluginConfig.resetSessionOnNewCampaign) {
           amplitude.setSessionId(Date.now());
           config.loggerProvider.log('Created a new session for new campaign.');