Cache Key V3 Fix (#434)

src/StatsigStore.ts

@@ -78,7 +78,7 @@ type APIInitializeDataWithDeltas = APIInitializeData & {
   };
 };
 
-type APIInitializeDataWithPrefetchedUsers = APIInitializeData & {
+export type APIInitializeDataWithPrefetchedUsers = APIInitializeData & {
   prefetched_user_values?: Record<string, APIInitializeData>;
 };
 
@@ -87,7 +87,7 @@ type APIInitializeDataWithDeltasWithPrefetchedUsers =
     prefetched_user_values?: Record<string, APIInitializeDataWithDeltas>;
   };
 
-type UserCacheValues = APIInitializeDataWithPrefetchedUsers & {
+export type UserCacheValues = APIInitializeDataWithPrefetchedUsers & {
   sticky_experiments: Record<string, APIDynamicConfig | undefined>;
   evaluation_time?: number;
   user_hash?: string;
@@ -453,6 +453,20 @@ export default class StatsigStore {
     await this.writeValuesToStorage(copiedValues);
   }
 
+  public getDeltasMergeFunction(
+    mergedValues: Record<string, UserCacheValues>,
+  ): (user: UserCacheValues, key: UserCacheKey) => UserCacheValues {
+    return (deltas, key) => {
+      const baseValues =
+        mergedValues[key.v3] ??
+        mergedValues[key.v2] ??
+        mergedValues[key.v1] ??
+        this.getDefaultUserCacheValues();
+
+      return this.mergeUserCacheValues(baseValues, deltas);
+    };
+  }
+
   public async saveInitDeltas(
     user: StatsigUser | null,
     response: Record<string, unknown>,
@@ -475,12 +489,7 @@ export default class StatsigStore {
       mergedValues,
       requestedUserCacheKey,
       user,
-      (deltas, key) => {
-        const baseValues =
-          mergedValues[key] ?? this.getDefaultUserCacheValues();
-
-        return this.mergeUserCacheValues(baseValues, deltas);
-      },
+      this.getDeltasMergeFunction(mergedValues),
       prefetchUsers,
     );
     let hasBadHash = false;
@@ -642,12 +651,12 @@ export default class StatsigStore {
   /**
    * Merges the provided init configs into the provided config map, according to the provided merge function
    */
-  private mergeInitializeResponseIntoUserMap(
+  public mergeInitializeResponseIntoUserMap(
     data: APIInitializeDataWithPrefetchedUsers,
     configMap: Record<string, UserCacheValues | undefined>,
     requestedUserCacheKey: UserCacheKey,
     user: StatsigUser | null,
-    mergeFn: (user: UserCacheValues, key: string) => UserCacheValues,
+    mergeFn: (user: UserCacheValues, key: UserCacheKey) => UserCacheValues,
     prefetchUsers?: Record<string, StatsigUser>,
   ) {
     if (data.prefetched_user_values) {
@@ -656,7 +665,7 @@ export default class StatsigStore {
         const prefetched = data.prefetched_user_values[key];
         const values = mergeFn(
           this.convertAPIDataToCacheValues(prefetched, key),
-          key,
+          { v1: key, v2: key, v3: key },
         );
         if (prefetchUsers) {
           const userHash = djb2HashForObject(prefetchUsers[key]);
@@ -681,7 +690,7 @@ export default class StatsigStore {
 
       configMap[requestedUserCacheKey.v3] = mergeFn(
         requestedUserValues,
-        requestedUserCacheKey.v3,
+        requestedUserCacheKey,
       );
     }
   }

src/__tests__/DeltasMerge.test.ts

@@ -0,0 +1,76 @@
+import StatsigClient from '../StatsigClient';
+import {
+  APIInitializeDataWithPrefetchedUsers,
+  UserCacheValues,
+} from '../StatsigStore';
+
+describe('On merge deltas', () => {
+  test('V2 values merge correctly', async () => {
+    const statsig = new StatsigClient(
+      'client-key',
+      {},
+      {
+        overrideStableID: '123',
+      },
+    );
+    const data: APIInitializeDataWithPrefetchedUsers = {
+      feature_gates: {
+        a_gate: {
+          value: true,
+          rule_id: '123',
+          name: 'a_gate',
+          secondary_exposures: [],
+        },
+      },
+      dynamic_configs: {},
+      layer_configs: {},
+      time: 2,
+    };
+    const mergedValues: Record<string, UserCacheValues> = {
+      v2_key: {
+        feature_gates: {
+          a_gate: {
+            value: false,
+            rule_id: 'default',
+            name: 'a_gate',
+            secondary_exposures: [],
+          },
+          b_gate: {
+            value: true,
+            rule_id: 'default',
+            name: 'b_gate',
+            secondary_exposures: [],
+          },
+        },
+        dynamic_configs: {},
+        layer_configs: {},
+        time: 0,
+        sticky_experiments: {},
+      },
+    };
+    statsig
+      .getStore()
+      .mergeInitializeResponseIntoUserMap(
+        data,
+        mergedValues,
+        { v1: 'v1_key', v2: 'v2_key', v3: 'v3_key' },
+        {},
+        statsig.getStore().getDeltasMergeFunction(mergedValues),
+      );
+    expect(mergedValues.v3_key.feature_gates).toEqual({
+      a_gate: {
+        value: true,
+        rule_id: '123',
+        name: 'a_gate',
+        secondary_exposures: [],
+      },
+      b_gate: {
+        value: true,
+        rule_id: 'default',
+        name: 'b_gate',
+        secondary_exposures: [],
+      },
+    });
+    expect(mergedValues.v3_key.time).toEqual(2);
+  });
+});