67 lines
No EOL
2.3 KiB
JavaScript
67 lines
No EOL
2.3 KiB
JavaScript
'use strict';
|
|
|
|
Object.defineProperty(exports, "__esModule", {
|
|
value: true
|
|
});
|
|
exports.default = ensureAsync;
|
|
|
|
var _setImmediate = require('./internal/setImmediate.js');
|
|
|
|
var _setImmediate2 = _interopRequireDefault(_setImmediate);
|
|
|
|
var _wrapAsync = require('./internal/wrapAsync.js');
|
|
|
|
function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
|
|
|
|
/**
|
|
* Wrap an async function and ensure it calls its callback on a later tick of
|
|
* the event loop. If the function already calls its callback on a next tick,
|
|
* no extra deferral is added. This is useful for preventing stack overflows
|
|
* (`RangeError: Maximum call stack size exceeded`) and generally keeping
|
|
* [Zalgo](http://blog.izs.me/post/59142742143/designing-apis-for-asynchrony)
|
|
* contained. ES2017 `async` functions are returned as-is -- they are immune
|
|
* to Zalgo's corrupting influences, as they always resolve on a later tick.
|
|
*
|
|
* @name ensureAsync
|
|
* @static
|
|
* @memberOf module:Utils
|
|
* @method
|
|
* @category Util
|
|
* @param {AsyncFunction} fn - an async function, one that expects a node-style
|
|
* callback as its last argument.
|
|
* @returns {AsyncFunction} Returns a wrapped function with the exact same call
|
|
* signature as the function passed in.
|
|
* @example
|
|
*
|
|
* function sometimesAsync(arg, callback) {
|
|
* if (cache[arg]) {
|
|
* return callback(null, cache[arg]); // this would be synchronous!!
|
|
* } else {
|
|
* doSomeIO(arg, callback); // this IO would be asynchronous
|
|
* }
|
|
* }
|
|
*
|
|
* // this has a risk of stack overflows if many results are cached in a row
|
|
* async.mapSeries(args, sometimesAsync, done);
|
|
*
|
|
* // this will defer sometimesAsync's callback if necessary,
|
|
* // preventing stack overflows
|
|
* async.mapSeries(args, async.ensureAsync(sometimesAsync), done);
|
|
*/
|
|
function ensureAsync(fn) {
|
|
if ((0, _wrapAsync.isAsync)(fn)) return fn;
|
|
return function (...args /*, callback*/) {
|
|
var callback = args.pop();
|
|
var sync = true;
|
|
args.push((...innerArgs) => {
|
|
if (sync) {
|
|
(0, _setImmediate2.default)(() => callback(...innerArgs));
|
|
} else {
|
|
callback(...innerArgs);
|
|
}
|
|
});
|
|
fn.apply(this, args);
|
|
sync = false;
|
|
};
|
|
}
|
|
module.exports = exports['default']; |