import { polyfillNeeded } from './utils.js';
/**
* Note: the "fetch.Request" default value is available for fetch imported from
* the "node-fetch" package and not in browsers. This is OK since browsers
* will be importing umd-polyfill.js from that path "self" is passed the
* decorator so the default value will not be used (because browsers that define
* fetch also has Request). One quirky setup where self.fetch exists but
* self.Request does not is when the "unfetch" minimal fetch polyfill is used
* on top of IE11; for this case the browser will try to use the fetch.Request
* default value which in turn will be undefined but then then "if (Request)"
* will ensure that you get a patched fetch but still no Request (as expected).
* @param {fetch, Request = fetch.Request}
* @returns {fetch: abortableFetch, Request: AbortableRequest}
*/
export default function abortableFetchDecorator(patchTargets) {
if ('function' === typeof patchTargets) {
patchTargets = { fetch: patchTargets };
}
const {
fetch,
Request: NativeRequest = fetch.Request,
AbortController: NativeAbortController,
__FORCE_INSTALL_ABORTCONTROLLER_POLYFILL = false,
} = patchTargets;
if (
!polyfillNeeded({
fetch,
Request: NativeRequest,
AbortController: NativeAbortController,
__FORCE_INSTALL_ABORTCONTROLLER_POLYFILL,
})
) {
return { fetch, Request };
}
let Request = NativeRequest;
// Note that the "unfetch" minimal fetch polyfill defines fetch() without
// defining window.Request, and this polyfill need to work on top of unfetch
// hence we only patch it if it's available. Also we don't patch it if signal
// is already available on the Request prototype because in this case support
// is present and the patching below can cause a crash since it assigns to
// request.signal which is technically a read-only property. This latter error
// happens when you run the main5.js node-fetch example in the repo
// "abortcontroller-polyfill-examples". The exact error is:
// request.signal = init.signal;
// ^
// TypeError: Cannot set property signal of #<Request> which has only a getter
if ((Request && !Request.prototype.hasOwnProperty('signal')) || __FORCE_INSTALL_ABORTCONTROLLER_POLYFILL) {
Request = function Request(input, init) {
let signal;
if (init && init.signal) {
signal = init.signal;
// Never pass init.signal to the native Request implementation when the polyfill has
// been installed because if we're running on top of a browser with a
// working native AbortController (i.e. the polyfill was installed due to
// __FORCE_INSTALL_ABORTCONTROLLER_POLYFILL being set), then passing our
// fake AbortSignal to the native fetch will trigger:
// TypeError: Failed to construct 'Request': member signal is not of type AbortSignal.
delete init.signal;
}
const request = new NativeRequest(input, init);
if (signal) {
Object.defineProperty(request, 'signal', {
writable: false,
enumerable: false,
configurable: true,
value: signal,
});
}
return request;
};
Request.prototype = NativeRequest.prototype;
}
const realFetch = fetch;
const abortableFetch = (input, init) => {
const signal = Request && Request.prototype.isPrototypeOf(input) ? input.signal : init ? init.signal : undefined;
if (signal) {
let abortError;
try {
abortError = new DOMException('Aborted', 'AbortError');
} catch (err) {
// IE 11 does not support calling the DOMException constructor, use a
// regular error object on it instead.
abortError = new Error('Aborted');
abortError.name = 'AbortError';
}
// Return early if already aborted, thus avoiding making an HTTP request
if (signal.aborted) {
return Promise.reject(abortError);
}
// Turn an event into a promise, reject it once `abort` is dispatched
const cancellation = new Promise((_, reject) => {
signal.addEventListener('abort', () => reject(abortError), { once: true });
});
if (init && init.signal) {
// Never pass .signal to the native implementation when the polyfill has
// been installed because if we're running on top of a browser with a
// working native AbortController (i.e. the polyfill was installed due to
// __FORCE_INSTALL_ABORTCONTROLLER_POLYFILL being set), then passing our
// fake AbortSignal to the native fetch will trigger:
// TypeError: Failed to execute 'fetch' on 'Window': member signal is not of type AbortSignal.
delete init.signal;
}
// Return the fastest promise (don't need to wait for request to finish)
return Promise.race([cancellation, realFetch(input, init)]);
}
return realFetch(input, init);
};
return { fetch: abortableFetch, Request };
}