Polyfill Promise.withResolvers for node 20 tests

packages/bbrt/src/test/node/util/fake-driver.ts

@@ -8,6 +8,7 @@ import type {
   BBRTDriverSendOptions,
 } from "../../../drivers/driver-interface.js";
 import type { TurnChunk } from "../../../state/turn-chunk.js";
+import "./install-promise-with-resolvers-polyfill.js";
 
 type SyncHandler = (opts: BBRTDriverSendOptions) => TurnChunk[];
 type AsyncHandler = (opts: BBRTDriverSendOptions) => AsyncIterable<TurnChunk>;

packages/bbrt/src/test/node/util/install-promise-with-resolvers-polyfill.ts

@@ -0,0 +1,20 @@
+/**
+ * @license
+ * Copyright 2024 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+// TODO(aomarks) Promise.withResolvers is available in all browsers, and Node
+// 22. See if we can update the GitHub Actions runner version to 22, and if so
+// we can delete this polyfill.
+if (Promise.withResolvers === undefined) {
+  Promise.withResolvers = <T>(): PromiseWithResolvers<T> => {
+    let resolve!: (value: T | PromiseLike<T>) => void;
+    let reject!: (reason?: unknown) => void;
+    const promise = new Promise<T>((res, rej) => {
+      resolve = res;
+      reject = rej;
+    });
+    return { promise, resolve, reject };
+  };
+}