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add
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'use strict';
Object.defineProperty(exports, "__esModule", {
value: true
});
exports.default = ensureAsync;
var _setImmediate = require('./internal/setImmediate');
var _setImmediate2 = _interopRequireDefault(_setImmediate);
var _initialParams = require('./internal/initialParams');
var _initialParams2 = _interopRequireDefault(_initialParams);
var _wrapAsync = require('./internal/wrapAsync');
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 (0, _initialParams2.default)(function (args, callback) {
var sync = true;
args.push(function () {
var innerArgs = arguments;
if (sync) {
(0, _setImmediate2.default)(function () {
callback.apply(null, innerArgs);
});
} else {
callback.apply(null, innerArgs);
}
});
fn.apply(this, args);
sync = false;
});
}
module.exports = exports['default'];
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