Process experiment metadata in RC fetch response

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

@@ -41,6 +41,8 @@ export function fetchConfig(remoteConfig: RemoteConfig): Promise<void>;
 export interface FetchResponse {
     config?: FirebaseRemoteConfigObject;
     eTag?: string;
+    // Warning: (ae-forgotten-export) The symbol "FirebaseExperimentDescription" needs to be exported by the entry point index.d.ts
+    experiments?: FirebaseExperimentDescription[];
     status: number;
     templateVersion?: number;
 }

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\[\] | 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.

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

@@ -48,6 +48,32 @@ interface FetchRequestBody {
   /* eslint-enable camelcase */
 }
 
+/**
+ * Defines experiment and variant attached to a config parameter.
+ */
+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[];
+}
+
 /**
  * Implements the Client abstraction for the Remote Config REST API.
  */
@@ -143,6 +169,7 @@ 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 +185,7 @@ export class RestClient implements RemoteConfigFetchClient {
       config = responseBody['entries'];
       state = responseBody['state'];
       templateVersion = responseBody['templateVersion'];
+      experiments = responseBody['experimentDescriptions'];
     }
 
     // Normalizes based on legacy state.
@@ -168,6 +196,7 @@ 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 +209,6 @@ 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

@@ -16,6 +16,7 @@
  */
 
 import { FirebaseApp, FirebaseError } from '@firebase/app';
+import { FirebaseExperimentDescription } from './client/rest_client';
 
 /**
  * The Firebase Remote Config service interface.
@@ -99,8 +100,12 @@ 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/test/api.test.ts

@@ -68,7 +68,16 @@ describe('Remote Config API', () => {
     status: 200,
     eTag: 'asdf',
     config: { 'foobar': 'hello world' },
-    templateVersion: 1
+    templateVersion: 1,
+    experiments: [
+      {
+        experimentId: '_exp_1',
+        variantId: '1',
+        experimentStartTime: '2025-04-06T14:13:57.597Z',
+        triggerTimeoutMillis: '15552000000',
+        timeToLiveMillis: '15552000000'
+      }
+    ]
   };
   let fetchStub: sinon.SinonStub;
 
@@ -106,7 +115,8 @@ describe('Remote Config API', () => {
           Promise.resolve({
             entries: response.config,
             state: 'OK',
-            templateVersion: response.templateVersion
+            templateVersion: response.templateVersion,
+            experimentDescriptions: response.experiments
           })
       } as Response)
     );

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

@@ -78,7 +78,16 @@ describe('RestClient', () => {
         eTag: 'etag',
         state: 'UPDATE',
         entries: { color: 'sparkling' },
-        templateVersion: 1
+        templateVersion: 1,
+        experimentDescriptions: [
+          {
+            experimentId: '_exp_1',
+            variantId: '1',
+            experimentStartTime: '2025-04-06T14:13:57.597Z',
+            triggerTimeoutMillis: '15552000000',
+            timeToLiveMillis: '15552000000'
+          }
+        ]
       };
 
       fetchStub.returns(
@@ -90,7 +99,8 @@ describe('RestClient', () => {
             Promise.resolve({
               entries: expectedResponse.entries,
               state: expectedResponse.state,
-              templateVersion: expectedResponse.templateVersion
+              templateVersion: expectedResponse.templateVersion,
+              experimentDescriptions: expectedResponse.experimentDescriptions
             })
         } as Response)
       );
@@ -101,7 +111,8 @@ describe('RestClient', () => {
         status: expectedResponse.status,
         eTag: expectedResponse.eTag,
         config: expectedResponse.entries,
-        templateVersion: expectedResponse.templateVersion
+        templateVersion: expectedResponse.templateVersion,
+        experiments: expectedResponse.experimentDescriptions
       });
     });
 
@@ -191,7 +202,8 @@ describe('RestClient', () => {
         status: 304,
         eTag: 'response-etag',
         config: undefined,
-        templateVersion: undefined
+        templateVersion: undefined,
+        experiments: undefined
       });
     });
 
@@ -230,7 +242,8 @@ describe('RestClient', () => {
         status: 304,
         eTag: 'etag',
         config: undefined,
-        templateVersion: undefined
+        templateVersion: undefined,
+        experiments: undefined
       });
     });
 
@@ -248,7 +261,8 @@ describe('RestClient', () => {
           status: 200,
           eTag: 'etag',
           config: {},
-          templateVersion: undefined
+          templateVersion: undefined,
+          experiments: []
         });
       }
     });

packages/remote-config/test/remote_config.test.ts

@@ -391,6 +391,15 @@ describe('RemoteConfig', () => {
     const CONFIG = { key: 'val' };
     const NEW_ETAG = 'new_etag';
     const TEMPLATE_VERSION = 1;
+    const EXPERIMENTS = [
+      {
+        'experimentId': '_exp_1',
+        'variantId': '1',
+        'experimentStartTime': '2025-04-06T14:13:57.597Z',
+        'triggerTimeoutMillis': '15552000000',
+        'timeToLiveMillis': '15552000000'
+      }
+    ];
 
     let getLastSuccessfulFetchResponseStub: sinon.SinonStub;
     let getActiveConfigEtagStub: sinon.SinonStub;
@@ -456,7 +465,8 @@ describe('RemoteConfig', () => {
         Promise.resolve({
           config: CONFIG,
           eTag: NEW_ETAG,
-          templateVersion: TEMPLATE_VERSION
+          templateVersion: TEMPLATE_VERSION,
+          experiments: EXPERIMENTS
         })
       );
       getActiveConfigEtagStub.returns(Promise.resolve(ETAG));
@@ -476,7 +486,8 @@ describe('RemoteConfig', () => {
         Promise.resolve({
           config: CONFIG,
           eTag: NEW_ETAG,
-          templateVersion: TEMPLATE_VERSION
+          templateVersion: TEMPLATE_VERSION,
+          experiments: EXPERIMENTS
         })
       );
       getActiveConfigEtagStub.returns(Promise.resolve());