feat(core): Add support for listing experiments (#12495)

packages/core/src/code_assist/experiments/client_metadata.ts

@@ -0,0 +1,55 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { getReleaseChannel } from '../../utils/channel.js';
+import type { ClientMetadata, Platform } from './types.js';
+import { fileURLToPath } from 'node:url';
+import path from 'node:path';
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
+
+// Cache all client metadata.
+let clientMetadataPromise: Promise<ClientMetadata> | undefined;
+
+function getPlatform(): Platform {
+  const platform = process.platform;
+  const arch = process.arch;
+
+  if (platform === 'darwin' && arch === 'x64') {
+    return 'DARWIN_AMD64';
+  }
+  if (platform === 'darwin' && arch === 'arm64') {
+    return 'DARWIN_ARM64';
+  }
+  if (platform === 'linux' && arch === 'x64') {
+    return 'LINUX_AMD64';
+  }
+  if (platform === 'linux' && arch === 'arm64') {
+    return 'LINUX_ARM64';
+  }
+  if (platform === 'win32' && arch === 'x64') {
+    return 'WINDOWS_AMD64';
+  }
+  return 'PLATFORM_UNSPECIFIED';
+}
+
+/**
+ * Returns the client metadata.
+ *
+ * The client metadata is cached so that it is only computed once per session.
+ */
+export async function getClientMetadata(): Promise<ClientMetadata> {
+  if (!clientMetadataPromise) {
+    clientMetadataPromise = (async () => ({
+      ide_type: 'GEMINI_CLI',
+      ide_version: process.env['CLI_VERSION'] || process.version,
+      platform: getPlatform(),
+      update_channel: await getReleaseChannel(__dirname),
+    }))();
+  }
+  return await clientMetadataPromise;
+}

packages/core/src/code_assist/experiments/experiments.ts

@@ -0,0 +1,49 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import type { CodeAssistServer } from '../server.js';
+import { getClientMetadata } from './client_metadata.js';
+import type { ListExperimentsResponse, Flag } from './types.js';
+
+export interface Experiments {
+  flags: Record<string, Flag>;
+  experimentIds: number[];
+}
+
+let experimentsPromise: Promise<Experiments> | undefined;
+
+/**
+ * Gets the experiments from the server.
+ *
+ * The experiments are cached so that they are only fetched once.
+ */
+export async function getExperiments(
+  server: CodeAssistServer,
+): Promise<Experiments> {
+  if (experimentsPromise) {
+    return await experimentsPromise;
+  }
+
+  experimentsPromise = (async () => {
+    const metadata = await getClientMetadata();
+    const response = await server.listExperiments(metadata);
+    return parseExperiments(response);
+  })();
+  return await experimentsPromise;
+}
+
+function parseExperiments(response: ListExperimentsResponse): Experiments {
+  const flags: Record<string, Flag> = {};
+  for (const flag of response.flags ?? []) {
+    if (flag.name) {
+      flags[flag.name] = flag;
+    }
+  }
+  return {
+    flags,
+    experimentIds: response.experiment_ids ?? [],
+  };
+}

packages/core/src/code_assist/experiments/types.ts

@@ -0,0 +1,58 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+export interface ListExperimentsRequest {
+  project: string;
+  metadata?: ClientMetadata;
+}
+
+export interface ListExperimentsResponse {
+  experiment_ids?: number[];
+  flags?: Flag[];
+  filtered_flags?: FilteredFlag[];
+  debug_string?: string;
+}
+
+export interface Flag {
+  name?: string;
+  bool_value?: boolean;
+  float_value?: number;
+  int_value?: string; // int64
+  string_value?: string;
+  int32_list_value?: Int32List;
+  string_list_value?: StringList;
+}
+
+export interface Int32List {
+  values?: number[];
+}
+
+export interface StringList {
+  values?: string[];
+}
+
+export interface FilteredFlag {
+  name?: string;
+  reason?: string;
+}
+
+export interface ClientMetadata {
+  ide_type?: IdeType;
+  ide_version?: string;
+  platform?: Platform;
+  update_channel?: 'nightly' | 'preview' | 'stable';
+  duet_project?: string;
+}
+
+export type IdeType = 'GEMINI_CLI';
+
+export type Platform =
+  | 'PLATFORM_UNSPECIFIED'
+  | 'DARWIN_AMD64'
+  | 'DARWIN_ARM64'
+  | 'LINUX_AMD64'
+  | 'LINUX_ARM64'
+  | 'WINDOWS_AMD64';