Integrate experiments with firebase analytics internal

common/api-review/remote-config.api.md

@@ -41,6 +41,7 @@ export function fetchConfig(remoteConfig: RemoteConfig): Promise<void>;
 export interface FetchResponse {
     config?: FirebaseRemoteConfigObject;
     eTag?: string;
+    experiments?: FirebaseExperimentDescription[];
     status: number;
     templateVersion?: number;
 }
@@ -51,6 +52,22 @@ export type FetchStatus = 'no-fetch-yet' | 'success' | 'failure' | 'throttle';
 // @public
 export type FetchType = 'BASE' | 'REALTIME';
 
+// @public
+export interface FirebaseExperimentDescription {
+    // (undocumented)
+    affectedParameterKeys?: string[];
+    // (undocumented)
+    experimentId: string;
+    // (undocumented)
+    experimentStartTime: string;
+    // (undocumented)
+    timeToLiveMillis: string;
+    // (undocumented)
+    triggerTimeoutMillis: string;
+    // (undocumented)
+    variantId: string;
+}
+
 // @public
 export interface FirebaseRemoteConfigObject {
     // (undocumented)

docs-devsite/_toc.yaml

@@ -649,6 +649,8 @@ toc:
     path: /docs/reference/js/remote-config.customsignals.md
   - title: FetchResponse
     path: /docs/reference/js/remote-config.fetchresponse.md
+  - title: FirebaseExperimentDescription
+    path: /docs/reference/js/remote-config.firebaseexperimentdescription.md
   - title: FirebaseRemoteConfigObject
     path: /docs/reference/js/remote-config.firebaseremoteconfigobject.md
   - title: RemoteConfig

docs-devsite/remote-config.fetchresponse.md

@@ -26,6 +26,7 @@ export interface FetchResponse
 |  --- | --- | --- |
 |  [config](./remote-config.fetchresponse.md#fetchresponseconfig) | [FirebaseRemoteConfigObject](./remote-config.firebaseremoteconfigobject.md#firebaseremoteconfigobject_interface) | Defines the map of parameters returned as "entries" in the fetch response body.<p>Only defined for 200 responses. |
 |  [eTag](./remote-config.fetchresponse.md#fetchresponseetag) | string | Defines the ETag response header value.<p>Only defined for 200 and 304 responses. |
+|  [experiments](./remote-config.fetchresponse.md#fetchresponseexperiments) | [FirebaseExperimentDescription](./remote-config.firebaseexperimentdescription.md#firebaseexperimentdescription_interface)<!-- -->\[\] | A/B Test and Rollout experiment metadata. |
 |  [status](./remote-config.fetchresponse.md#fetchresponsestatus) | number | The HTTP status, which is useful for differentiating success responses with data from those without.<p>The Remote Config client is modeled after the native <code>Fetch</code> interface, so HTTP status is first-class.<p>Disambiguation: the fetch response returns a legacy "state" value that is redundant with the HTTP status code. The former is normalized into the latter. |
 |  [templateVersion](./remote-config.fetchresponse.md#fetchresponsetemplateversion) | number | The version number of the config template fetched from the server. |
 
@@ -53,6 +54,18 @@ Defines the ETag response header value.
 eTag?: string;
 ```
 
+## FetchResponse.experiments
+
+A/B Test and Rollout experiment metadata.
+
+Only defined for 200 responses.
+
+<b>Signature:</b>
+
+```typescript
+experiments?: FirebaseExperimentDescription[];
+```
+
 ## FetchResponse.status
 
 The HTTP status, which is useful for differentiating success responses with data from those without.

docs-devsite/remote-config.firebaseexperimentdescription.md

@@ -0,0 +1,78 @@
+Project: /docs/reference/js/_project.yaml
+Book: /docs/reference/_book.yaml
+page_type: reference
+
+{% comment %}
+DO NOT EDIT THIS FILE!
+This is generated by the JS SDK team, and any local changes will be
+overwritten. Changes should be made in the source code at
+https://github.com/firebase/firebase-js-sdk
+{% endcomment %}
+
+# FirebaseExperimentDescription interface
+Defines experiment and variant attached to a config parameter.
+
+<b>Signature:</b>
+
+```typescript
+export interface FirebaseExperimentDescription 
+```
+
+## Properties
+
+|  Property | Type | Description |
+|  --- | --- | --- |
+|  [affectedParameterKeys](./remote-config.firebaseexperimentdescription.md#firebaseexperimentdescriptionaffectedparameterkeys) | string\[\] |  |
+|  [experimentId](./remote-config.firebaseexperimentdescription.md#firebaseexperimentdescriptionexperimentid) | string |  |
+|  [experimentStartTime](./remote-config.firebaseexperimentdescription.md#firebaseexperimentdescriptionexperimentstarttime) | string |  |
+|  [timeToLiveMillis](./remote-config.firebaseexperimentdescription.md#firebaseexperimentdescriptiontimetolivemillis) | string |  |
+|  [triggerTimeoutMillis](./remote-config.firebaseexperimentdescription.md#firebaseexperimentdescriptiontriggertimeoutmillis) | string |  |
+|  [variantId](./remote-config.firebaseexperimentdescription.md#firebaseexperimentdescriptionvariantid) | string |  |
+
+## FirebaseExperimentDescription.affectedParameterKeys
+
+<b>Signature:</b>
+
+```typescript
+affectedParameterKeys?: string[];
+```
+
+## FirebaseExperimentDescription.experimentId
+
+<b>Signature:</b>
+
+```typescript
+experimentId: string;
+```
+
+## FirebaseExperimentDescription.experimentStartTime
+
+<b>Signature:</b>
+
+```typescript
+experimentStartTime: string;
+```
+
+## FirebaseExperimentDescription.timeToLiveMillis
+
+<b>Signature:</b>
+
+```typescript
+timeToLiveMillis: string;
+```
+
+## FirebaseExperimentDescription.triggerTimeoutMillis
+
+<b>Signature:</b>
+
+```typescript
+triggerTimeoutMillis: string;
+```
+
+## FirebaseExperimentDescription.variantId
+
+<b>Signature:</b>
+
+```typescript
+variantId: string;
+```

docs-devsite/remote-config.md

@@ -42,6 +42,7 @@ The Firebase Remote Config Web SDK. This SDK does not work in a Node.js environm
 |  [ConfigUpdateObserver](./remote-config.configupdateobserver.md#configupdateobserver_interface) | Observer interface for receiving real-time Remote Config update notifications.<!-- -->NOTE: Although an <code>complete</code> callback can be provided, it will never be called because the ConfigUpdate stream is never-ending. |
 |  [CustomSignals](./remote-config.customsignals.md#customsignals_interface) | Defines the type for representing custom signals and their values.<p>The values in CustomSignals must be one of the following types:<ul> <li><code>string</code> <li><code>number</code> <li><code>null</code> </ul> |
 |  [FetchResponse](./remote-config.fetchresponse.md#fetchresponse_interface) | Defines a successful response (200 or 304).<p>Modeled after the native <code>Response</code> interface, but simplified for Remote Config's use case. |
+|  [FirebaseExperimentDescription](./remote-config.firebaseexperimentdescription.md#firebaseexperimentdescription_interface) | Defines experiment and variant attached to a config parameter. |
 |  [FirebaseRemoteConfigObject](./remote-config.firebaseremoteconfigobject.md#firebaseremoteconfigobject_interface) | Defines a self-descriptive reference for config key-value pairs. |
 |  [RemoteConfig](./remote-config.remoteconfig.md#remoteconfig_interface) | The Firebase Remote Config service interface. |
 |  [RemoteConfigOptions](./remote-config.remoteconfigoptions.md#remoteconfigoptions_interface) | Options for Remote Config initialization. |

packages/remote-config/src/abt/experiment.ts

@@ -0,0 +1,90 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import { Storage } from '../storage/storage';
+import { FirebaseExperimentDescription } from '../public_types';
+import { Provider } from '@firebase/component';
+import { FirebaseAnalyticsInternalName } from '@firebase/analytics-interop-types';
+
+export class Experiment {
+  constructor(
+    private readonly storage: Storage,
+    private readonly analyticsProvider: Provider<FirebaseAnalyticsInternalName>
+  ) {}
+
+  async updateActiveExperiments(
+    latestExperiments: FirebaseExperimentDescription[]
+  ): Promise<void> {
+    const currentActiveExperiments =
+      (await this.storage.getActiveExperiments()) || new Set<string>();
+    const experimentInfoMap = this.createExperimentInfoMap(latestExperiments);
+    this.addActiveExperiments(currentActiveExperiments, experimentInfoMap);
+    this.removeInactiveExperiments(currentActiveExperiments, experimentInfoMap);
+    return this.storage.setActiveExperiments(new Set(experimentInfoMap.keys()));
+  }
+
+  private createExperimentInfoMap(
+    latestExperiments: FirebaseExperimentDescription[]
+  ): Map<string, FirebaseExperimentDescription> {
+    const experimentInfoMap = new Map<string, FirebaseExperimentDescription>();
+    for (const experiment of latestExperiments) {
+      experimentInfoMap.set(experiment.experimentId, experiment);
+    }
+    return experimentInfoMap;
+  }
+
+  private addActiveExperiments(
+    currentActiveExperiments: Set<string>,
+    experimentInfoMap: Map<string, FirebaseExperimentDescription>
+  ): void {
+    for (const [experimentId, experimentInfo] of experimentInfoMap.entries()) {
+      if (!currentActiveExperiments.has(experimentId)) {
+        void this.addExperimentToAnalytics(
+          experimentId,
+          experimentInfo.variantId
+        );
+      }
+    }
+  }
+
+  private removeInactiveExperiments(
+    currentActiveExperiments: Set<string>,
+    experimentInfoMap: Map<string, FirebaseExperimentDescription>
+  ): void {
+    for (const experimentId of currentActiveExperiments) {
+      if (!experimentInfoMap.has(experimentId)) {
+        void this.removeExperimentFromAnalytics(experimentId);
+      }
+    }
+  }
+
+  private async addExperimentToAnalytics(
+    experimentId: string,
+    variantId: string | null
+  ): Promise<void> {
+    const analytics = await this.analyticsProvider.get();
+    const customProperty = {
+      [experimentId]: variantId
+    };
+    analytics.setUserProperties({ properties: customProperty });
+  }
+
+  private async removeExperimentFromAnalytics(
+    experimentId: string
+  ): Promise<void> {
+    void this.addExperimentToAnalytics(experimentId, null);
+  }
+}

packages/remote-config/src/api.ts

@@ -36,6 +36,7 @@ import { ERROR_FACTORY, ErrorCode, hasErrorCode } from './errors';
 import { RemoteConfig as RemoteConfigImpl } from './remote_config';
 import { Value as ValueImpl } from './value';
 import { LogLevel as FirebaseLogLevel } from '@firebase/logger';
+import { Experiment } from './abt/experiment';
 
 /**
  *
@@ -110,12 +111,18 @@ export async function activate(remoteConfig: RemoteConfig): Promise<boolean> {
     // config.
     return false;
   }
+  const experiment = new Experiment(rc._storage, rc._analyticsProvider);
   await Promise.all([
     rc._storageCache.setActiveConfig(lastSuccessfulFetchResponse.config),
     rc._storage.setActiveConfigEtag(lastSuccessfulFetchResponse.eTag),
     rc._storage.setActiveConfigTemplateVersion(
       lastSuccessfulFetchResponse.templateVersion
-    )
+    ),
+    lastSuccessfulFetchResponse.experiments &&
+      experiment.updateActiveExperiments(
+        lastSuccessfulFetchResponse.experiments
+      ),
+    rc._storage.setActiveConfigEtag(lastSuccessfulFetchResponse.eTag)
   ]);
   return true;
 }

packages/remote-config/src/client/rest_client.ts

@@ -18,7 +18,8 @@
 import {
   CustomSignals,
   FetchResponse,
-  FirebaseRemoteConfigObject
+  FirebaseRemoteConfigObject,
+  FirebaseExperimentDescription
 } from '../public_types';
 import {
   RemoteConfigFetchClient,
@@ -143,6 +144,7 @@ export class RestClient implements RemoteConfigFetchClient {
     let config: FirebaseRemoteConfigObject | undefined;
     let state: string | undefined;
     let templateVersion: number | undefined;
+    let experiments: FirebaseExperimentDescription[] | undefined;
 
     // JSON parsing throws SyntaxError if the response body isn't a JSON string.
     // Requesting application/json and checking for a 200 ensures there's JSON data.
@@ -158,6 +160,7 @@ export class RestClient implements RemoteConfigFetchClient {
       config = responseBody['entries'];
       state = responseBody['state'];
       templateVersion = responseBody['templateVersion'];
+      experiments = responseBody['experimentDescriptions'];
     }
 
     // Normalizes based on legacy state.
@@ -168,6 +171,7 @@ export class RestClient implements RemoteConfigFetchClient {
     } else if (state === 'NO_TEMPLATE' || state === 'EMPTY_CONFIG') {
       // These cases can be fixed remotely, so normalize to safe value.
       config = {};
+      experiments = [];
     }
 
     // Normalize to exception-based control flow for non-success cases.
@@ -180,6 +184,6 @@ export class RestClient implements RemoteConfigFetchClient {
       });
     }
 
-    return { status, eTag: responseEtag, config, templateVersion };
+    return { status, eTag: responseEtag, config, templateVersion, experiments };
   }
 }

packages/remote-config/src/public_types.ts

@@ -59,6 +59,34 @@ export interface FirebaseRemoteConfigObject {
   [key: string]: string;
 }
 
+/**
+ * Defines experiment and variant attached to a config parameter.
+ *
+ * @public
+ */
+export interface FirebaseExperimentDescription {
+  // A string of max length 22 characters and of format: _exp_<experiment_id>
+  experimentId: string;
+
+  // The variant of the experiment assigned to the app instance.
+  variantId: string;
+
+  // When the experiment was started.
+  experimentStartTime: string;
+
+  // How long the experiment can remain in STANDBY state. Valid range from 1 ms
+  // to 6 months.
+  triggerTimeoutMillis: string;
+
+  // How long the experiment can remain in ON state. Valid range from 1 ms to 6
+  // months.
+  timeToLiveMillis: string;
+
+  // A repeated of Remote Config parameter keys that this experiment is
+  // affecting the value of.
+  affectedParameterKeys?: string[];
+}
+
 /**
  * Defines a successful response (200 or 304).
  *
@@ -99,8 +127,12 @@ export interface FetchResponse {
    */
   templateVersion?: number;
 
-  // Note: we're not extracting experiment metadata until
-  // ABT and Analytics have Web SDKs.
+  /**
+   * A/B Test and Rollout experiment metadata.
+   *
+   * @remarks Only defined for 200 responses.
+   */
+  experiments?: FirebaseExperimentDescription[];
 }
 
 /**

packages/remote-config/src/register.ts

@@ -66,6 +66,7 @@ export function registerRemoteConfig(): void {
     const installations = container
       .getProvider('installations-internal')
       .getImmediate();
+    const analyticsProvider = container.getProvider('analytics-internal');
 
     // Normalizes optional inputs.
     const { projectId, apiKey, appId } = app.options;
@@ -127,7 +128,8 @@ export function registerRemoteConfig(): void {
       storageCache,
       storage,
       logger,
-      realtimeHandler
+      realtimeHandler,
+      analyticsProvider
     );
 
     // Starts warming cache.