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Diffstat (limited to 'node_modules/async/ensureAsync.js')
-rw-r--r-- | node_modules/async/ensureAsync.js | 67 |
1 files changed, 67 insertions, 0 deletions
diff --git a/node_modules/async/ensureAsync.js b/node_modules/async/ensureAsync.js new file mode 100644 index 0000000..ad8beb5 --- /dev/null +++ b/node_modules/async/ensureAsync.js @@ -0,0 +1,67 @@ +'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'];
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