File Explorer

1"use strict";2/*3 * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.4 * SPDX-License-Identifier: Apache-2.0.5 */6Object.defineProperty(exports, "__esModule", { value: true });7exports.newLiftedPromise = exports.makeSelfCleaningPromise = void 0;8/**9 * A helper function that takes a promise and creates a wrapper promise that invokes a cleanup function when the inner10 * promise is completed for any reason.  The primary use is to remove event listeners related to promise completion11 * when the promise actually completes.  This allows us to keep the number of listeners on a CancelController bounded by12 * the number of incomplete promises associated with it.  If we didn't clean up, the listener set would grow13 * without limit.14 *15 * For cancellation, this leads to an internal usage pattern that is strongly recommended:16 *17 * ```18 * async doSomethingCancellable(...) : Promise<...> {19 *    removeListenerFunctor = undefined;20 *21 *    innerPromise = new Promise(async (resolve, reject) => {22 *       ...23 *24 *       cancelListenerFunction = () => { clean up and reject innerPromise };25 *       removeListenerFunctor = cancelController.addListener(cancelListenerFunction);26 *27 *       ...28 *    }29 *30 *    return makeSelfCleaningPromise(innerPromise, removeListenerFunctor);31 * }32 * ```33 *34 * @param promise promise to wrap with automatic cleanup35 * @param cleaner cleaner function to invoke when the promise is completed36 *37 * @return a promise with matching result/err, that invokes the cleaner function on inner promise completion38 */39function makeSelfCleaningPromise(promise, cleaner) {40    if (!cleaner) {41        return promise;42    }43    return promise.finally(() => { cleaner(); });44}45exports.makeSelfCleaningPromise = makeSelfCleaningPromise;46/**47 * Factory function to create a new LiftedPromise48 *49 * @param promiseBody optional body function to invoke as part of promise creation50 *51 * @return a promise whose resolve and reject methods have been lifted out of the internal body function and made52 * available to external actors53 */54function newLiftedPromise(promiseBody) {55    let localResolve = undefined;56    let localReject = undefined;57    let promise = new Promise((resolve, reject) => {58        localResolve = resolve;59        localReject = reject;60    });61    if (!localResolve || !localReject) {62        // should never happen63        throw new Error("Failed to bind resolve and reject when making lifted promise");64    }65    if (promiseBody) {66        promiseBody(localResolve, localReject);67    }68    return {69        promise: promise,70        resolve: localResolve,71        reject: localReject72    };73}74exports.newLiftedPromise = newLiftedPromise;75//# sourceMappingURL=promise.js.map