1 | ;
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2 |
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3 | Object.defineProperty(exports, "__esModule", {
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4 | value: true
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5 | });
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6 | exports.default = ensureAsync;
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7 |
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8 | var _setImmediate = require('./internal/setImmediate.js');
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9 |
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10 | var _setImmediate2 = _interopRequireDefault(_setImmediate);
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11 |
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12 | var _wrapAsync = require('./internal/wrapAsync.js');
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13 |
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14 | function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
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15 |
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16 | /**
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17 | * Wrap an async function and ensure it calls its callback on a later tick of
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18 | * the event loop. If the function already calls its callback on a next tick,
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19 | * no extra deferral is added. This is useful for preventing stack overflows
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20 | * (`RangeError: Maximum call stack size exceeded`) and generally keeping
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21 | * [Zalgo](http://blog.izs.me/post/59142742143/designing-apis-for-asynchrony)
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22 | * contained. ES2017 `async` functions are returned as-is -- they are immune
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23 | * to Zalgo's corrupting influences, as they always resolve on a later tick.
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24 | *
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25 | * @name ensureAsync
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26 | * @static
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27 | * @memberOf module:Utils
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28 | * @method
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29 | * @category Util
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30 | * @param {AsyncFunction} fn - an async function, one that expects a node-style
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31 | * callback as its last argument.
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32 | * @returns {AsyncFunction} Returns a wrapped function with the exact same call
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33 | * signature as the function passed in.
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34 | * @example
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35 | *
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36 | * function sometimesAsync(arg, callback) {
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37 | * if (cache[arg]) {
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38 | * return callback(null, cache[arg]); // this would be synchronous!!
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39 | * } else {
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40 | * doSomeIO(arg, callback); // this IO would be asynchronous
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41 | * }
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42 | * }
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43 | *
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44 | * // this has a risk of stack overflows if many results are cached in a row
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45 | * async.mapSeries(args, sometimesAsync, done);
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46 | *
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47 | * // this will defer sometimesAsync's callback if necessary,
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48 | * // preventing stack overflows
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49 | * async.mapSeries(args, async.ensureAsync(sometimesAsync), done);
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50 | */
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51 | function ensureAsync(fn) {
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52 | if ((0, _wrapAsync.isAsync)(fn)) return fn;
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53 | return function (...args /*, callback*/) {
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54 | var callback = args.pop();
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55 | var sync = true;
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56 | args.push((...innerArgs) => {
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57 | if (sync) {
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58 | (0, _setImmediate2.default)(() => callback(...innerArgs));
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59 | } else {
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60 | callback(...innerArgs);
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61 | }
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62 | });
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63 | fn.apply(this, args);
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64 | sync = false;
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65 | };
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66 | }
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67 | module.exports = exports.default; |
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