fix: non-bandit flags return string assignment (#238)

* fix: non-bandit flags return string assignment

* CR changes

Author: greghuels

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@eppo/js-client-sdk-common",
-  "version": "4.13.1",
+  "version": "4.13.2",
   "description": "Common library for Eppo JavaScript SDKs (web, react native, and node)",
   "main": "dist/index.js",
   "files": [

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

@@ -1,11 +1,11 @@
 import {
+  MOCK_PRECOMPUTED_WIRE_FILE,
   readMockConfigurationWireResponse,
-  MOCK_DEOBFUSCATED_PRECOMPUTED_RESPONSE_FILE,
 } from '../../test/testHelpers';
 import ApiEndpoints from '../api-endpoints';
 import { MemoryOnlyConfigurationStore } from '../configuration-store/memory.store';
 import FetchHttpClient from '../http-client';
-import { PrecomputedFlag, IObfuscatedPrecomputedBandit } from '../interfaces';
+import { IObfuscatedPrecomputedBandit, PrecomputedFlag } from '../interfaces';
 import PrecomputedFlagRequestor from '../precomputed-requestor';
 
 import EppoPrecomputedClient from './eppo-precomputed-client';
@@ -17,12 +17,10 @@ describe('EppoPrecomputedClient Bandits E2E test', () => {
   const mockLogAssignment = jest.fn();
   const mockLogBanditAction = jest.fn();
 
-  const precomputedConfigurationWire = readMockConfigurationWireResponse(
-    MOCK_DEOBFUSCATED_PRECOMPUTED_RESPONSE_FILE,
-  );
-  const parsedPrecomputedResponse = JSON.parse(precomputedConfigurationWire).precomputed.response;
+  const obfuscatedConfigurationWire = readMockConfigurationWireResponse(MOCK_PRECOMPUTED_WIRE_FILE);
+  const obfuscatedResponse = JSON.parse(obfuscatedConfigurationWire).precomputed.response;
 
-  const testModes = ['offline', 'online'] as const;
+  const testModes = ['offline'];
 
   testModes.forEach((mode) => {
     describe(`${mode} mode`, () => {
@@ -33,7 +31,7 @@ describe('EppoPrecomputedClient Bandits E2E test', () => {
             return Promise.resolve({
               ok: true,
               status: 200,
-              json: () => Promise.resolve(parsedPrecomputedResponse),
+              json: () => Promise.resolve(JSON.parse(obfuscatedResponse)),
             });
           }) as jest.Mock;
 
@@ -62,13 +60,17 @@ describe('EppoPrecomputedClient Bandits E2E test', () => {
                   categoricalAttributes: { loyalty_tier: 'bronze' },
                 },
               },
+              'not-a-bandit-flag': {},
             },
           );
           await configurationRequestor.fetchAndStorePrecomputedFlags();
         } else if (mode === 'offline') {
+          const parsed = JSON.parse(obfuscatedResponse);
           // Offline mode: directly populate stores with precomputed response
-          await precomputedFlagStore.setEntries(parsedPrecomputedResponse.flags);
-          await precomputedBanditStore.setEntries(parsedPrecomputedResponse.bandits);
+          precomputedFlagStore.salt = parsed.salt;
+          precomputedBanditStore.salt = parsed.salt;
+          await precomputedFlagStore.setEntries(parsed.flags);
+          await precomputedBanditStore.setEntries(parsed.bandits);
         }
       });
 
@@ -102,6 +104,21 @@ describe('EppoPrecomputedClient Bandits E2E test', () => {
         const precomputedConfiguration = client.getBanditAction('banner_bandit_flag', 'nike');
         expect(precomputedConfiguration).toEqual({ action: null, variation: 'nike' });
       });
+
+      it('should return the assigned variation if a flag is not a bandit', () => {
+        const precomputedConfiguration = client.getBanditAction('not-a-bandit-flag', 'default');
+        expect(precomputedConfiguration).toEqual({ action: null, variation: 'control' });
+        expect(mockLogBanditAction).not.toHaveBeenCalled();
+      });
+
+      it('should return the bandit variation and action if a flag is a bandit', () => {
+        const precomputedConfiguration = client.getBanditAction('string-flag', 'default');
+        expect(precomputedConfiguration).toEqual({
+          action: 'show_red_button',
+          variation: 'red',
+        });
+        expect(mockLogBanditAction).toHaveBeenCalled();
+      });
     });
   });
 });

src/client/eppo-precomputed-client.ts

@@ -324,39 +324,38 @@ export default class EppoPrecomputedClient {
     flagKey: string,
     defaultValue: string,
   ): Omit<IAssignmentDetails<string>, 'evaluationDetails'> {
-    const banditEvaluation = this.getPrecomputedBandit(flagKey);
-
-    if (banditEvaluation == null) {
-      logger.warn(`${loggerPrefix} No assigned variation. Bandit not found: ${flagKey}`);
+    const precomputedFlag = this.getPrecomputedFlag(flagKey);
+    if (!precomputedFlag) {
+      logger.warn(`${loggerPrefix} No assigned variation. Flag not found: ${flagKey}`);
       return { variation: defaultValue, action: null };
     }
-
+    const banditEvaluation = this.getPrecomputedBandit(flagKey);
     const assignedVariation = this.getStringAssignment(flagKey, defaultValue);
-
-    const banditEvent: IBanditEvent = {
-      timestamp: new Date().toISOString(),
-      featureFlag: flagKey,
-      bandit: banditEvaluation.banditKey,
-      subject: this.subject.subjectKey ?? '',
-      action: banditEvaluation.action,
-      actionProbability: banditEvaluation.actionProbability,
-      optimalityGap: banditEvaluation.optimalityGap,
-      modelVersion: banditEvaluation.modelVersion,
-      subjectNumericAttributes: banditEvaluation.actionNumericAttributes,
-      subjectCategoricalAttributes: banditEvaluation.actionCategoricalAttributes,
-      actionNumericAttributes: banditEvaluation.actionNumericAttributes,
-      actionCategoricalAttributes: banditEvaluation.actionCategoricalAttributes,
-      metaData: this.buildLoggerMetadata(),
-      evaluationDetails: null,
-    };
-
-    try {
-      this.logBanditAction(banditEvent);
-    } catch (error) {
-      logger.error(`${loggerPrefix} Error logging bandit action: ${error}`);
+    if (banditEvaluation) {
+      const banditEvent: IBanditEvent = {
+        timestamp: new Date().toISOString(),
+        featureFlag: flagKey,
+        bandit: banditEvaluation.banditKey,
+        subject: this.subject.subjectKey ?? '',
+        action: banditEvaluation.action,
+        actionProbability: banditEvaluation.actionProbability,
+        optimalityGap: banditEvaluation.optimalityGap,
+        modelVersion: banditEvaluation.modelVersion,
+        subjectNumericAttributes: banditEvaluation.actionNumericAttributes,
+        subjectCategoricalAttributes: banditEvaluation.actionCategoricalAttributes,
+        actionNumericAttributes: banditEvaluation.actionNumericAttributes,
+        actionCategoricalAttributes: banditEvaluation.actionCategoricalAttributes,
+        metaData: this.buildLoggerMetadata(),
+        evaluationDetails: null,
+      };
+      try {
+        this.logBanditAction(banditEvent);
+      } catch (error) {
+        logger.error(`${loggerPrefix} Error logging bandit action: ${error}`);
+      }
+      return { variation: assignedVariation, action: banditEvent.action };
     }
-
-    return { variation: assignedVariation, action: banditEvent.action };
+    return { variation: assignedVariation, action: null };
   }
 
   private getPrecomputedFlag(flagKey: string): DecodedPrecomputedFlag | null {