feat: add user agent to requests

sdk/analytics.ts

@@ -1,6 +1,7 @@
 import { pino, Logger } from 'pino';
 import { Fetch } from './types.js';
 import { FlagsmithConfig } from './types.js';
+import { getUserAgent } from './utils.js';
 
 export const ANALYTICS_ENDPOINT = './analytics/flags/';
 
@@ -69,7 +70,8 @@ export class AnalyticsProcessor {
                 signal: AbortSignal.timeout(this.requestTimeoutMs),
                 headers: {
                     'Content-Type': 'application/json',
-                    'X-Environment-Key': this.environmentKey
+                    'X-Environment-Key': this.environmentKey,
+                    'User-Agent': getUserAgent()
                 }
             });
             await this.currentFlush;

sdk/index.ts

@@ -14,7 +14,7 @@ import { FlagsmithAPIError } from './errors.js';
 
 import { DefaultFlag, Flags } from './models.js';
 import { EnvironmentDataPollingManager } from './polling_manager.js';
-import { Deferred, generateIdentitiesData, retryFetch } from './utils.js';
+import { Deferred, generateIdentitiesData, getUserAgent, retryFetch } from './utils.js';
 import { SegmentModel } from '../flagsmith-engine/index.js';
 import { getIdentitySegments } from '../flagsmith-engine/segments/evaluators.js';
 import {
@@ -335,6 +335,8 @@ export class Flagsmith {
             headers['X-Environment-Key'] = this.environmentKey as string;
         }
 
+        headers['User-Agent'] = getUserAgent();
+
         if (this.customHeaders) {
             for (const [k, v] of Object.entries(this.customHeaders)) {
                 headers[k] = v;

sdk/utils.ts

@@ -3,6 +3,9 @@ import { Dispatcher } from 'undici-types';
 
 type Traits = { [key: string]: TraitConfig | FlagsmithTraitValue };
 
+const FLAGSMITH_USER_AGENT = 'flagsmith-nodejs-sdk';
+const FLAGSMITH_UNKNOWN_VERSION = 'unknown';
+
 export function isTraitConfig(
     traitValue: TraitConfig | FlagsmithTraitValue
 ): traitValue is TraitConfig {
@@ -102,3 +105,13 @@ export class Deferred<T> {
         this.rejectPromise(reason);
     }
 }
+
+export function getUserAgent(): string {
+    try {
+        const packageJson = require('../package.json');
+        const version = packageJson?.version;
+        return version ? `${FLAGSMITH_USER_AGENT}/${version}` : FLAGSMITH_UNKNOWN_VERSION;
+    } catch {
+        return FLAGSMITH_UNKNOWN_VERSION;
+    }
+}

tests/sdk/analytics.test.ts

@@ -1,3 +1,4 @@
+import { getUserAgent } from '../../sdk/utils.js';
 import { analyticsProcessor, fetch } from './utils.js';
 
 test('test_analytics_processor_track_feature_updates_analytics_data', () => {
@@ -26,7 +27,11 @@ test('test_analytics_processor_flush_post_request_data_match_ananlytics_data', a
         'http://testUrl/analytics/flags/',
         expect.objectContaining({
             body: '{"myFeature1":1,"myFeature2":1}',
-            headers: { 'Content-Type': 'application/json', 'X-Environment-Key': 'test-key' },
+            headers: {
+                'Content-Type': 'application/json',
+                'X-Environment-Key': 'test-key',
+                'User-Agent': getUserAgent()
+            },
             method: 'POST'
         })
     );

tests/sdk/flagsmith-environment-flags.test.ts

@@ -1,6 +1,7 @@
 import Flagsmith from '../../sdk/index.js';
 import { environmentJSON, environmentModel, flagsJSON, flagsmith, fetch } from './utils.js';
 import { DefaultFlag } from '../../sdk/models.js';
+import { getUserAgent } from '../../sdk/utils.js';
 
 vi.mock('../../sdk/polling_manager');
 
@@ -72,6 +73,33 @@ test('test_getFeatureValue', async () => {
     expect(featureValue).toBe('some-value');
 });
 
+test('test_user_agent_is_set_when_fetching_environment_flags', async () => {
+    const defaultFlag = new DefaultFlag('some-default-value', true);
+
+    const defaultFlagHandler = (featureName: string) => defaultFlag;
+
+    const flg = flagsmith({
+        environmentKey: 'key',
+        defaultFlagHandler: defaultFlagHandler,
+        enableAnalytics: true
+    });
+    const flags = await flg.getEnvironmentFlags();
+    const featureValue = flags.getFeatureValue('some_feature');
+
+    expect(featureValue).toBe('some-value');
+    expect(fetch).toHaveBeenCalledWith(
+        `https://edge.api.flagsmith.com/api/v1/flags/`,
+        expect.objectContaining({
+            method: 'GET',
+            headers: {
+                'Content-Type': 'application/json',
+                'X-Environment-Key': 'key',
+                'User-Agent': getUserAgent()
+            }
+        })
+    );
+});
+
 test('test_throws_when_no_default_flag_handler_after_multiple_API_errors', async () => {
     fetch.mockRejectedValue('Error during fetching the API response');
 

tests/sdk/flagsmith-identity-flags.test.ts

@@ -9,6 +9,7 @@ import {
     badFetch
 } from './utils.js';
 import { DefaultFlag } from '../../sdk/models.js';
+import { getUserAgent } from '../../sdk/utils.js';
 
 vi.mock('../../sdk/polling_manager');
 
@@ -150,7 +151,11 @@ test('test_transient_identity', async () => {
         `https://edge.api.flagsmith.com/api/v1/identities/`,
         expect.objectContaining({
             method: 'POST',
-            headers: { 'Content-Type': 'application/json', 'X-Environment-Key': 'sometestfakekey' },
+            headers: {
+                'Content-Type': 'application/json',
+                'X-Environment-Key': 'sometestfakekey',
+                'User-Agent': getUserAgent()
+            },
             body: JSON.stringify({ identifier, traits: traitsInRequest, transient })
         })
     );
@@ -191,7 +196,11 @@ test('test_identity_with_transient_traits', async () => {
         `https://edge.api.flagsmith.com/api/v1/identities/`,
         expect.objectContaining({
             method: 'POST',
-            headers: { 'Content-Type': 'application/json', 'X-Environment-Key': 'sometestfakekey' },
+            headers: {
+                'Content-Type': 'application/json',
+                'X-Environment-Key': 'sometestfakekey',
+                'User-Agent': getUserAgent()
+            },
             body: JSON.stringify({ identifier, traits: traitsInRequest })
         })
     );

tests/sdk/flagsmith.test.ts

@@ -9,7 +9,7 @@ import {
     badFetch
 } from './utils.js';
 import { DefaultFlag, Flags } from '../../sdk/models.js';
-import { delay } from '../../sdk/utils.js';
+import { delay, getUserAgent } from '../../sdk/utils.js';
 import { EnvironmentModel } from '../../flagsmith-engine/environments/models.js';
 import { BaseOfflineHandler } from '../../sdk/offline_handlers.js';
 import { Agent } from 'undici';
@@ -358,3 +358,10 @@ test('getIdentityFlags succeeds if initial fetch failed then succeeded', async (
     const flags2 = await flg.getIdentityFlags('test-user');
     expect(flags2.isFeatureEnabled('some_feature')).toBe(true);
 });
+
+test('get_user_agent_extracts_version_from_package_json', async () => {
+    const userAgent = getUserAgent();
+    const packageJson = require('../../package.json');
+
+    expect(userAgent).toBe(`flagsmith-nodejs-sdk/${packageJson.version}`);
+});