From 6c7c3bacebe3f8c6077f5d2532d5a06259e374bf Mon Sep 17 00:00:00 2001
From: Tim Yiu <137842098+tyiuhc@users.noreply.github.com>
Date: Fri, 10 Jan 2025 14:35:25 -0800
Subject: [PATCH] feat: migrate to use web_exp_id for web experiment device_id
 bucketing (#154)

---
 packages/experiment-tag/src/experiment.ts     | 35 +++++++++----------
 .../experiment-tag/test/experiment.test.ts    |  3 +-
 2 files changed, 18 insertions(+), 20 deletions(-)

diff --git a/packages/experiment-tag/src/experiment.ts b/packages/experiment-tag/src/experiment.ts
index dcc3e37..6a1bcfe 100644
--- a/packages/experiment-tag/src/experiment.ts
+++ b/packages/experiment-tag/src/experiment.ts
@@ -59,24 +59,23 @@ export const initializeExperiment = async (
     user = {};
   }
 
-  // create new user if it does not exist, or it does not have device_id or web_exp_id
-  if (Object.keys(user).length === 0 || !user.device_id || !user.web_exp_id) {
-    if (!user.device_id || !user.web_exp_id) {
-      // if user has device_id, migrate it to web_exp_id
-      if (user.device_id) {
-        user.web_exp_id = user.device_id;
-      } else if (user.web_exp_id) {
-        user.device_id = user.web_exp_id;
-      } else {
-        const uuid = UUID();
-        // both IDs are set for backwards compatibility, to be removed in future update
-        user = { device_id: uuid, web_exp_id: uuid };
-      }
-      globalScope.localStorage.setItem(
-        experimentStorageName,
-        JSON.stringify(user),
-      );
-    }
+  // if web_exp_id does not exist:
+  // 1. if device_id exists, migrate device_id to web_exp_id and remove device_id
+  // 2. if device_id does not exist, create a new web_exp_id
+  // 3. if both device_id and web_exp_id exist, remove device_id
+  if (!user.web_exp_id) {
+    user.web_exp_id = user.device_id || UUID();
+    delete user.device_id;
+    globalScope.localStorage.setItem(
+      experimentStorageName,
+      JSON.stringify(user),
+    );
+  } else if (user.web_exp_id && user.device_id) {
+    delete user.device_id;
+    globalScope.localStorage.setItem(
+      experimentStorageName,
+      JSON.stringify(user),
+    );
   }
 
   const urlParams = getUrlParams();
diff --git a/packages/experiment-tag/test/experiment.test.ts b/packages/experiment-tag/test/experiment.test.ts
index 4838e52..71fec36 100644
--- a/packages/experiment-tag/test/experiment.test.ts
+++ b/packages/experiment-tag/test/experiment.test.ts
@@ -55,12 +55,11 @@ describe('initializeExperiment', () => {
   test('should initialize experiment with empty user', () => {
     initializeExperiment(stringify(apiKey), JSON.stringify([]));
     expect(ExperimentClient.prototype.setUser).toHaveBeenCalledWith({
-      device_id: 'mock',
       web_exp_id: 'mock',
     });
     expect(mockGlobal.localStorage.setItem).toHaveBeenCalledWith(
       'EXP_1',
-      JSON.stringify({ device_id: 'mock', web_exp_id: 'mock' }),
+      JSON.stringify({ web_exp_id: 'mock' }),
     );
   });