feat: persist subject key and attributes for precomputed logging (#163)

* Persist with instance variables

* setSubjectDataAndPrecomputedFlagStore and tests

* Include logging in test

* Rename function

* v4.6.1

* Update description

* Make method to set subject from PrecomputedFlagsRequestParameters

* Description update

package.json

@@ -1,7 +1,7 @@
 {
   "name": "@eppo/js-client-sdk-common",
-  "version": "4.6.0",
-  "description": "Eppo SDK for client-side JavaScript applications (base for both web and react native)",
+  "version": "4.6.1",
+  "description": "Common library for Eppo JavaScript SDKs (web, react native, and node)",
   "main": "dist/index.js",
   "files": [
     "/dist",

src/client/eppo-precomputed-client.spec.ts

@@ -430,7 +430,8 @@ describe('EppoPrecomputedClient E2E test', () => {
     });
 
     it('Fetches initial configuration with parameters in constructor', async () => {
-      client = new EppoPrecomputedClient(precomputedFlagStore, requestParameters);
+      client = new EppoPrecomputedClient(precomputedFlagStore);
+      client.setSubjectAndPrecomputedFlagsRequestParameters(requestParameters);
       // no configuration loaded
       let variation = client.getStringAssignment(precomputedFlagKey, 'default');
       expect(variation).toBe('default');
@@ -442,7 +443,7 @@ describe('EppoPrecomputedClient E2E test', () => {
 
     it('Fetches initial configuration with parameters provided later', async () => {
       client = new EppoPrecomputedClient(precomputedFlagStore);
-      client.setPrecomputedFlagsRequestParameters(requestParameters);
+      client.setSubjectAndPrecomputedFlagsRequestParameters(requestParameters);
       // no configuration loaded
       let variation = client.getStringAssignment(precomputedFlagKey, 'default');
       expect(variation).toBe('default');
@@ -462,7 +463,8 @@ describe('EppoPrecomputedClient E2E test', () => {
           }
         }
 
-        client = new EppoPrecomputedClient(new MockStore(), {
+        client = new EppoPrecomputedClient(new MockStore());
+        client.setSubjectAndPrecomputedFlagsRequestParameters({
           ...requestParameters,
           pollAfterSuccessfulInitialization: true,
         });
@@ -491,7 +493,8 @@ describe('EppoPrecomputedClient E2E test', () => {
         }
       }
 
-      client = new EppoPrecomputedClient(new MockStore(), requestParameters);
+      client = new EppoPrecomputedClient(new MockStore());
+      client.setSubjectAndPrecomputedFlagsRequestParameters(requestParameters);
       // no configuration loaded
       let variation = client.getStringAssignment(precomputedFlagKey, 'default');
       expect(variation).toBe('default');
@@ -505,7 +508,8 @@ describe('EppoPrecomputedClient E2E test', () => {
       let client: EppoPrecomputedClient;
 
       beforeEach(async () => {
-        client = new EppoPrecomputedClient(storage, requestParameters);
+        client = new EppoPrecomputedClient(storage);
+        client.setSubjectAndPrecomputedFlagsRequestParameters(requestParameters);
         await client.fetchPrecomputedFlags();
       });
 
@@ -576,7 +580,8 @@ describe('EppoPrecomputedClient E2E test', () => {
         ...requestParameters,
         pollAfterSuccessfulInitialization,
       };
-      client = new EppoPrecomputedClient(precomputedFlagStore, requestParameters);
+      client = new EppoPrecomputedClient(precomputedFlagStore);
+      client.setSubjectAndPrecomputedFlagsRequestParameters(requestParameters);
       // no configuration loaded
       let variation = client.getStringAssignment(precomputedFlagKey, 'default');
       expect(variation).toBe('default');
@@ -640,7 +645,8 @@ describe('EppoPrecomputedClient E2E test', () => {
         throwOnFailedInitialization,
         pollAfterFailedInitialization,
       };
-      client = new EppoPrecomputedClient(precomputedFlagStore, requestParameters);
+      client = new EppoPrecomputedClient(precomputedFlagStore);
+      client.setSubjectAndPrecomputedFlagsRequestParameters(requestParameters);
       // no configuration loaded
       expect(client.getStringAssignment(precomputedFlagKey, 'default')).toBe('default');
 
@@ -678,7 +684,7 @@ describe('EppoPrecomputedClient E2E test', () => {
           extraLogging: {},
         },
       });
-      client = new EppoPrecomputedClient(storage, undefined, true);
+      client = new EppoPrecomputedClient(storage, true);
     });
 
     afterAll(() => {
@@ -705,4 +711,51 @@ describe('EppoPrecomputedClient E2E test', () => {
 
     expect(loggedEvent.format).toEqual(FormatEnum.PRECOMPUTED);
   });
+
+  describe('EppoPrecomputedClient subject data and store initialization', () => {
+    let client: EppoPrecomputedClient;
+    let store: IConfigurationStore<PrecomputedFlag>;
+    let mockLogger: IAssignmentLogger;
+
+    beforeEach(() => {
+      store = new MemoryOnlyConfigurationStore<PrecomputedFlag>();
+      mockLogger = td.object<IAssignmentLogger>();
+      client = new EppoPrecomputedClient(store);
+      client.setAssignmentLogger(mockLogger);
+    });
+
+    it('returns default value and does not log when store is not initialized', () => {
+      client.setSubjectAndPrecomputedFlagStore('test-subject', {}, store);
+      expect(client.getStringAssignment('test-flag', 'default')).toBe('default');
+      expect(td.explain(mockLogger.logAssignment).callCount).toEqual(0);
+    });
+
+    it('returns assignment and logs subject data after store is initialized with flags', async () => {
+      const subjectKey = 'test-subject';
+      const subjectAttributes = { attr1: 'value1' };
+
+      await store.setEntries({
+        'test-flag': {
+          variationType: VariationType.STRING,
+          variationKey: 'control',
+          variationValue: 'test-value',
+          allocationKey: 'allocation-1',
+          doLog: true,
+          extraLogging: {},
+        },
+      });
+      client.setSubjectAndPrecomputedFlagStore(subjectKey, subjectAttributes, store);
+      expect(client.getStringAssignment('test-flag', 'default')).toBe('test-value');
+
+      expect(td.explain(mockLogger.logAssignment).callCount).toEqual(1);
+      const loggedEvent = td.explain(mockLogger.logAssignment).calls[0].args[0];
+      expect(loggedEvent.subject).toEqual(subjectKey);
+      expect(loggedEvent.subjectAttributes).toEqual(subjectAttributes);
+    });
+
+    it('returns default value and does not log when subject data is not set', () => {
+      expect(client.getStringAssignment('test-flag', 'default')).toBe('default');
+      expect(td.explain(mockLogger.logAssignment).callCount).toEqual(0);
+    });
+  });
 });

src/client/eppo-precomputed-client.ts

@@ -48,16 +48,20 @@ export default class EppoPrecomputedClient {
   private assignmentLogger?: IAssignmentLogger;
   private assignmentCache?: AssignmentCache;
   private requestPoller?: IPoller;
+  private precomputedFlagsRequestParameters?: PrecomputedFlagsRequestParameters;
+  private subjectKey?: string;
+  private subjectAttributes?: Attributes;
 
   constructor(
     private precomputedFlagStore: IConfigurationStore<PrecomputedFlag>,
-    private precomputedFlagsRequestParameters?: PrecomputedFlagsRequestParameters,
     private isObfuscated = false,
   ) {}
 
-  public setPrecomputedFlagsRequestParameters(
+  public setSubjectAndPrecomputedFlagsRequestParameters(
     precomputedFlagsRequestParameters: PrecomputedFlagsRequestParameters,
   ) {
+    this.subjectKey = precomputedFlagsRequestParameters.precompute.subjectKey;
+    this.subjectAttributes = precomputedFlagsRequestParameters.precompute.subjectAttributes;
     this.precomputedFlagsRequestParameters = precomputedFlagsRequestParameters;
   }
 
@@ -134,6 +138,19 @@ export default class EppoPrecomputedClient {
     }
   }
 
+  public setSubjectAndPrecomputedFlagStore(
+    subjectKey: string,
+    subjectAttributes: Attributes,
+    precomputedFlagStore: IConfigurationStore<PrecomputedFlag>,
+  ) {
+    // Save the new subject data and precomputed flag store together because they are related
+    // Stop any polling process if it exists from previous subject data to protect consistency
+    this.requestPoller?.stop();
+    this.setPrecomputedFlagStore(precomputedFlagStore);
+    this.subjectKey = subjectKey;
+    this.subjectAttributes = subjectAttributes;
+  }
+
   private getPrecomputedAssignment<T>(
     flagKey: string,
     defaultValue: T,
@@ -160,8 +177,8 @@ export default class EppoPrecomputedClient {
     const result: FlagEvaluationWithoutDetails = {
       flagKey,
       format: this.precomputedFlagStore.getFormat() ?? '',
-      subjectKey: this.precomputedFlagsRequestParameters?.precompute.subjectKey ?? '',
-      subjectAttributes: this.precomputedFlagsRequestParameters?.precompute.subjectAttributes ?? {},
+      subjectKey: this.subjectKey ?? '',
+      subjectAttributes: this.subjectAttributes ?? {},
       variation: {
         key: preComputedFlag.variationKey,
         value: preComputedFlag.variationValue,