mentoss/dist/custom-request.js

A utility to mock fetch requests and responses.

/**
 * @fileoverview A custom request class that allows for more control over requests.
 * @author Nicholas C. Zakas
 */
//-----------------------------------------------------------------------------
// Imports
//-----------------------------------------------------------------------------
import { assertValidNoCorsRequestInit } from "./cors.js";
//-----------------------------------------------------------------------------
// Exports
//-----------------------------------------------------------------------------
/**
 * Creates a custom request class that extends a given Request class.
 * @param {typeof Request} RequestClass The class to extend.
 * @returns {typeof Request} The custom request class.
 */
export function createCustomRequest(RequestClass) {
    return class CustomRequest extends RequestClass {
        /**
         * The ID of the request.
         * @type {string}
         */
        id = Math.random().toString(36).slice(2);
        /**
         * Creates a new instance.
         * @param {string|Request|URL} input The URL or Request object to fetch.
         * @param {RequestInit} [init] The options for the fetch.
         */
        constructor(input, init) {
            /*
             * Not all runtimes validate the `mode` property correctly.
             * To ensure consistency across runtimes, we do the validation
             * and throw a consistent error.
             */
            if (init?.mode === "no-cors") {
                assertValidNoCorsRequestInit(init);
            }
            super(input, init);
            // ensure id is not writable
            Object.defineProperty(this, "id", { writable: false });
            /*
             * Default setting for `mode` is "cors" in the fetch API.
             * Not all runtimes follow the spec, so we need to ensure
             * that the `mode` property is set correctly.
             */
            const expectedMode = init?.mode ?? "cors";
            if (expectedMode !== this.mode) {
                Object.defineProperty(this, "mode", {
                    configurable: true,
                    enumerable: true,
                    value: expectedMode,
                    writable: false,
                });
            }
            /*
             * Default setting for `redirect` is "follow" in the fetch API.
             * Not all runtimes follow the spec, so we need to ensure
             * that the `redirect` property is set correctly.
             */
            const expectedRedirect = init?.redirect ?? "follow";
            if (expectedRedirect !== this.redirect) {
                Object.defineProperty(this, "redirect", {
                    configurable: true,
                    enumerable: true,
                    value: expectedRedirect,
                    writable: false,
                });
            }
            /*
             * Not all runtimes properly support the `credentials` property.
             * Bun's fetch implementation sets credentials to "include" by default
             * and doesn't allow overwriting that value when creating a Request.
             * We therefore need to hack it together to make sure this works in
             * Bun correctly.
             * https://github.com/oven-sh/bun/issues/17052
             *
             * Deno doesn't support the `credentials` property on Request and
             * it's undefined so we need to fix that as well.
             */
            const expectedCredentials = init?.credentials ?? "same-origin";
            if (expectedCredentials !== this.credentials) {
                Object.defineProperty(this, "credentials", {
                    configurable: true,
                    enumerable: true,
                    value: expectedCredentials,
                    writable: false,
                });
            }
        }
        /**
         * Clones the request. Clones shared the same ID.
         * @returns {CustomRequest} A new instance of the request.
         */
        clone() {
            /*
             * This is a bit hacky. You can't create a new Request from
             * one that has already been used, so we first need to create
             * a clone of the request. Sadly, the clone is always a Request
             * instance, so we need to create a new CustomRequest instance
             * from that clone. This is the only way to ensure that the
             * clone has the same class as the original request.
             */
            const clonedRequest = new CustomRequest(super.clone());
            Object.defineProperty(clonedRequest, "id", { value: this.id });
            return clonedRequest;
        }
    };
}