fix: fix web attribution behavior for no referrer in the same session

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 isEventInNewSession = 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
+      isEventInNewSession
     ) {
       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 +1,6 @@
+export const isNewSession = (sessionTimeout: number, lastEventTime: number = Date.now()): boolean => {
+  const currentTime = 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 in a same session for undefined lastEventTime', () => {
+    const isEventInNewSession = isNewSession(sessionTimeout, undefined);
+
+    expect(isEventInNewSession).toBe(false);
+  });
+
+  test('should be a new session', () => {
+    const lastEventTime = Date.now() - sessionTimeout * 2;
+    const isEventInNewSession = isNewSession(sessionTimeout, lastEventTime);
+
+    expect(isEventInNewSession).toBe(true);
+  });
+
+  test('should be in a same session', () => {
+    const lastEventTime = Date.now();
+    const isEventInNewSession = isNewSession(sessionTimeout, lastEventTime);
+
+    expect(isEventInNewSession).toBe(false);
+  });
+});

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

@@ -17,13 +17,24 @@ const domainWithoutSubdomain = (domain: string) => {
   return parts.slice(parts.length - 2, parts.length).join('.');
 };
 
-export const isNewCampaign = (current: Campaign, previous: Campaign | undefined, options: Options) => {
+export const isNewCampaign = (
+  current: Campaign,
+  previous: Campaign | undefined,
+  options: Options,
+  isNewSession = true,
+) => {
   const { referrer, referring_domain, ...currentCampaign } = current;
   const { referrer: _previous_referrer, referring_domain: prevReferringDomain, ...previousCampaign } = previous || {};
 
   if (isExcludedReferrer(options.excludeReferrers, current.referring_domain)) {
     return false;
   }
+
+  //In the same session, no referrer should not override or unset any persisting query params
+  if (!isNewSession && !referrer && previous) {
+    return false;
+  }
+
   const hasNewCampaign = JSON.stringify(currentCampaign) !== JSON.stringify(previousCampaign);
   const hasNewDomain =
     domainWithoutSubdomain(referring_domain || '') !== domainWithoutSubdomain(prevReferringDomain || '');

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 = {
@@ -26,7 +27,9 @@ export const webAttributionPlugin: CreateWebAttributionPlugin = function (option
         storage.get(storageKey),
       ]);
 
-      if (isNewCampaign(currentCampaign, previousCampaign, pluginConfig)) {
+      const isEventInNewSession = isNewSession(config.sessionTimeout, config.lastEventTime);
+
+      if (isNewCampaign(currentCampaign, previousCampaign, pluginConfig, isEventInNewSession)) {
         if (pluginConfig.resetSessionOnNewCampaign) {
           amplitude.setSessionId(Date.now());
           config.loggerProvider.log('Created a new session for new campaign.');

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

@@ -112,6 +112,19 @@ describe('isNewCampaign', () => {
       }),
     ).toBe(false);
   });
+
+  test('should return false for no referrer in the same session', () => {
+    const previousCampaign = {
+      ...BASE_CAMPAIGN,
+      utm_campaign: 'utm_campaign',
+      referring_domain: 'a.b.c.d',
+    };
+    const currentCampaign = {
+      ...BASE_CAMPAIGN,
+    };
+
+    expect(isNewCampaign(currentCampaign, previousCampaign, {}, false)).toBe(false);
+  });
 });
 
 describe('isExcludedReferrer', () => {