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JavaScript
(function (global, factory) {
typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports) :
typeof define === 'function' && define.amd ? define(['exports'], factory) :
(global = typeof globalThis !== 'undefined' ? globalThis : global || self, factory(global.async = {}));
})(this, (function (exports) { 'use strict';
/**
* Creates a continuation function with some arguments already applied.
*
* Useful as a shorthand when combined with other control flow functions. Any
* arguments passed to the returned function are added to the arguments
* originally passed to apply.
*
* @name apply
* @static
* @memberOf module:Utils
* @method
* @category Util
* @param {Function} fn - The function you want to eventually apply all
* arguments to. Invokes with (arguments...).
* @param {...*} arguments... - Any number of arguments to automatically apply
* when the continuation is called.
* @returns {Function} the partially-applied function
* @example
*
* // using apply
* async.parallel([
* async.apply(fs.writeFile, 'testfile1', 'test1'),
* async.apply(fs.writeFile, 'testfile2', 'test2')
* ]);
*
*
* // the same process without using apply
* async.parallel([
* function(callback) {
* fs.writeFile('testfile1', 'test1', callback);
* },
* function(callback) {
* fs.writeFile('testfile2', 'test2', callback);
* }
* ]);
*
* // It's possible to pass any number of additional arguments when calling the
* // continuation:
*
* node> var fn = async.apply(sys.puts, 'one');
* node> fn('two', 'three');
* one
* two
* three
*/
function apply(fn, ...args) {
return (...callArgs) => fn(...args,...callArgs);
}
function initialParams (fn) {
return function (...args/*, callback*/) {
var callback = args.pop();
return fn.call(this, args, callback);
};
}
/* istanbul ignore file */
var hasQueueMicrotask = typeof queueMicrotask === 'function' && queueMicrotask;
var hasSetImmediate = typeof setImmediate === 'function' && setImmediate;
var hasNextTick = typeof process === 'object' && typeof process.nextTick === 'function';
function fallback(fn) {
setTimeout(fn, 0);
}
function wrap(defer) {
return (fn, ...args) => defer(() => fn(...args));
}
var _defer$1;
if (hasQueueMicrotask) {
_defer$1 = queueMicrotask;
} else if (hasSetImmediate) {
_defer$1 = setImmediate;
} else if (hasNextTick) {
_defer$1 = process.nextTick;
} else {
_defer$1 = fallback;
}
var setImmediate$1 = wrap(_defer$1);
/**
* Take a sync function and make it async, passing its return value to a
* callback. This is useful for plugging sync functions into a waterfall,
* series, or other async functions. Any arguments passed to the generated
* function will be passed to the wrapped function (except for the final
* callback argument). Errors thrown will be passed to the callback.
*
* If the function passed to `asyncify` returns a Promise, that promises's
* resolved/rejected state will be used to call the callback, rather than simply
* the synchronous return value.
*
* This also means you can asyncify ES2017 `async` functions.
*
* @name asyncify
* @static
* @memberOf module:Utils
* @method
* @alias wrapSync
* @category Util
* @param {Function} func - The synchronous function, or Promise-returning
* function to convert to an {@link AsyncFunction}.
* @returns {AsyncFunction} An asynchronous wrapper of the `func`. To be
* invoked with `(args..., callback)`.
* @example
*
* // passing a regular synchronous function
* async.waterfall([
* async.apply(fs.readFile, filename, "utf8"),
* async.asyncify(JSON.parse),
* function (data, next) {
* // data is the result of parsing the text.
* // If there was a parsing error, it would have been caught.
* }
* ], callback);
*
* // passing a function returning a promise
* async.waterfall([
* async.apply(fs.readFile, filename, "utf8"),
* async.asyncify(function (contents) {
* return db.model.create(contents);
* }),
* function (model, next) {
* // `model` is the instantiated model object.
* // If there was an error, this function would be skipped.
* }
* ], callback);
*
* // es2017 example, though `asyncify` is not needed if your JS environment
* // supports async functions out of the box
* var q = async.queue(async.asyncify(async function(file) {
* var intermediateStep = await processFile(file);
* return await somePromise(intermediateStep)
* }));
*
* q.push(files);
*/
function asyncify(func) {
if (isAsync(func)) {
return function (...args/*, callback*/) {
const callback = args.pop();
const promise = func.apply(this, args);
return handlePromise(promise, callback)
}
}
return initialParams(function (args, callback) {
var result;
try {
result = func.apply(this, args);
} catch (e) {
return callback(e);
}
// if result is Promise object
if (result && typeof result.then === 'function') {
return handlePromise(result, callback)
} else {
callback(null, result);
}
});
}
function handlePromise(promise, callback) {
return promise.then(value => {
invokeCallback(callback, null, value);
}, err => {
invokeCallback(callback, err && (err instanceof Error || err.message) ? err : new Error(err));
});
}
function invokeCallback(callback, error, value) {
try {
callback(error, value);
} catch (err) {
setImmediate$1(e => { throw e }, err);
}
}
function isAsync(fn) {
return fn[Symbol.toStringTag] === 'AsyncFunction';
}
function isAsyncGenerator(fn) {
return fn[Symbol.toStringTag] === 'AsyncGenerator';
}
function isAsyncIterable(obj) {
return typeof obj[Symbol.asyncIterator] === 'function';
}
function wrapAsync(asyncFn) {
if (typeof asyncFn !== 'function') throw new Error('expected a function')
return isAsync(asyncFn) ? asyncify(asyncFn) : asyncFn;
}
// conditionally promisify a function.
// only return a promise if a callback is omitted
function awaitify (asyncFn, arity) {
if (!arity) arity = asyncFn.length;
if (!arity) throw new Error('arity is undefined')
function awaitable (...args) {
if (typeof args[arity - 1] === 'function') {
return asyncFn.apply(this, args)
}
return new Promise((resolve, reject) => {
args[arity - 1] = (err, ...cbArgs) => {
if (err) return reject(err)
resolve(cbArgs.length > 1 ? cbArgs : cbArgs[0]);
};
asyncFn.apply(this, args);
})
}
return awaitable
}
function applyEach$1 (eachfn) {
return function applyEach(fns, ...callArgs) {
const go = awaitify(function (callback) {
var that = this;
return eachfn(fns, (fn, cb) => {
wrapAsync(fn).apply(that, callArgs.concat(cb));
}, callback);
});
return go;
};
}
function _asyncMap(eachfn, arr, iteratee, callback) {
arr = arr || [];
var results = [];
var counter = 0;
var _iteratee = wrapAsync(iteratee);
return eachfn(arr, (value, _, iterCb) => {
var index = counter++;
_iteratee(value, (err, v) => {
results[index] = v;
iterCb(err);
});
}, err => {
callback(err, results);
});
}
function isArrayLike(value) {
return value &&
typeof value.length === 'number' &&
value.length >= 0 &&
value.length % 1 === 0;
}
// A temporary value used to identify if the loop should be broken.
// See #1064, #1293
const breakLoop = {};
function once(fn) {
function wrapper (...args) {
if (fn === null) return;
var callFn = fn;
fn = null;
callFn.apply(this, args);
}
Object.assign(wrapper, fn);
return wrapper
}
function getIterator (coll) {
return coll[Symbol.iterator] && coll[Symbol.iterator]();
}
function createArrayIterator(coll) {
var i = -1;
var len = coll.length;
return function next() {
return ++i < len ? {value: coll[i], key: i} : null;
}
}
function createES2015Iterator(iterator) {
var i = -1;
return function next() {
var item = iterator.next();
if (item.done)
return null;
i++;
return {value: item.value, key: i};
}
}
function createObjectIterator(obj) {
var okeys = obj ? Object.keys(obj) : [];
var i = -1;
var len = okeys.length;
return function next() {
var key = okeys[++i];
if (key === '__proto__') {
return next();
}
return i < len ? {value: obj[key], key} : null;
};
}
function createIterator(coll) {
if (isArrayLike(coll)) {
return createArrayIterator(coll);
}
var iterator = getIterator(coll);
return iterator ? createES2015Iterator(iterator) : createObjectIterator(coll);
}
function onlyOnce(fn) {
return function (...args) {
if (fn === null) throw new Error("Callback was already called.");
var callFn = fn;
fn = null;
callFn.apply(this, args);
};
}
// for async generators
function asyncEachOfLimit(generator, limit, iteratee, callback) {
let done = false;
let canceled = false;
let awaiting = false;
let running = 0;
let idx = 0;
function replenish() {
//console.log('replenish')
if (running >= limit || awaiting || done) return
//console.log('replenish awaiting')
awaiting = true;
generator.next().then(({value, done: iterDone}) => {
//console.log('got value', value)
if (canceled || done) return
awaiting = false;
if (iterDone) {
done = true;
if (running <= 0) {
//console.log('done nextCb')
callback(null);
}
return;
}
running++;
iteratee(value, idx, iterateeCallback);
idx++;
replenish();
}).catch(handleError);
}
function iterateeCallback(err, result) {
//console.log('iterateeCallback')
running -= 1;
if (canceled) return
if (err) return handleError(err)
if (err === false) {
done = true;
canceled = true;
return
}
if (result === breakLoop || (done && running <= 0)) {
done = true;
//console.log('done iterCb')
return callback(null);
}
replenish();
}
function handleError(err) {
if (canceled) return
awaiting = false;
done = true;
callback(err);
}
replenish();
}
var eachOfLimit$2 = (limit) => {
return (obj, iteratee, callback) => {
callback = once(callback);
if (limit <= 0) {
throw new RangeError('concurrency limit cannot be less than 1')
}
if (!obj) {
return callback(null);
}
if (isAsyncGenerator(obj)) {
return asyncEachOfLimit(obj, limit, iteratee, callback)
}
if (isAsyncIterable(obj)) {
return asyncEachOfLimit(obj[Symbol.asyncIterator](), limit, iteratee, callback)
}
var nextElem = createIterator(obj);
var done = false;
var canceled = false;
var running = 0;
var looping = false;
function iterateeCallback(err, value) {
if (canceled) return
running -= 1;
if (err) {
done = true;
callback(err);
}
else if (err === false) {
done = true;
canceled = true;
}
else if (value === breakLoop || (done && running <= 0)) {
done = true;
return callback(null);
}
else if (!looping) {
replenish();
}
}
function replenish () {
looping = true;
while (running < limit && !done) {
var elem = nextElem();
if (elem === null) {
done = true;
if (running <= 0) {
callback(null);
}
return;
}
running += 1;
iteratee(elem.value, elem.key, onlyOnce(iterateeCallback));
}
looping = false;
}
replenish();
};
};
/**
* The same as [`eachOf`]{@link module:Collections.eachOf} but runs a maximum of `limit` async operations at a
* time.
*
* @name eachOfLimit
* @static
* @memberOf module:Collections
* @method
* @see [async.eachOf]{@link module:Collections.eachOf}
* @alias forEachOfLimit
* @category Collection
* @param {Array|Iterable|AsyncIterable|Object} coll - A collection to iterate over.
* @param {number} limit - The maximum number of async operations at a time.
* @param {AsyncFunction} iteratee - An async function to apply to each
* item in `coll`. The `key` is the item's key, or index in the case of an
* array.
* Invoked with (item, key, callback).
* @param {Function} [callback] - A callback which is called when all
* `iteratee` functions have finished, or an error occurs. Invoked with (err).
* @returns {Promise} a promise, if a callback is omitted
*/
function eachOfLimit(coll, limit, iteratee, callback) {
return eachOfLimit$2(limit)(coll, wrapAsync(iteratee), callback);
}
var eachOfLimit$1 = awaitify(eachOfLimit, 4);
// eachOf implementation optimized for array-likes
function eachOfArrayLike(coll, iteratee, callback) {
callback = once(callback);
var index = 0,
completed = 0,
{length} = coll,
canceled = false;
if (length === 0) {
callback(null);
}
function iteratorCallback(err, value) {
if (err === false) {
canceled = true;
}
if (canceled === true) return
if (err) {
callback(err);
} else if ((++completed === length) || value === breakLoop) {
callback(null);
}
}
for (; index < length; index++) {
iteratee(coll[index], index, onlyOnce(iteratorCallback));
}
}
// a generic version of eachOf which can handle array, object, and iterator cases.
function eachOfGeneric (coll, iteratee, callback) {
return eachOfLimit$1(coll, Infinity, iteratee, callback);
}
/**
* Like [`each`]{@link module:Collections.each}, except that it passes the key (or index) as the second argument
* to the iteratee.
*
* @name eachOf
* @static
* @memberOf module:Collections
* @method
* @alias forEachOf
* @category Collection
* @see [async.each]{@link module:Collections.each}
* @param {Array|Iterable|AsyncIterable|Object} coll - A collection to iterate over.
* @param {AsyncFunction} iteratee - A function to apply to each
* item in `coll`.
* The `key` is the item's key, or index in the case of an array.
* Invoked with (item, key, callback).
* @param {Function} [callback] - A callback which is called when all
* `iteratee` functions have finished, or an error occurs. Invoked with (err).
* @returns {Promise} a promise, if a callback is omitted
* @example
*
* // dev.json is a file containing a valid json object config for dev environment
* // dev.json is a file containing a valid json object config for test environment
* // prod.json is a file containing a valid json object config for prod environment
* // invalid.json is a file with a malformed json object
*
* let configs = {}; //global variable
* let validConfigFileMap = {dev: 'dev.json', test: 'test.json', prod: 'prod.json'};
* let invalidConfigFileMap = {dev: 'dev.json', test: 'test.json', invalid: 'invalid.json'};
*
* // asynchronous function that reads a json file and parses the contents as json object
* function parseFile(file, key, callback) {
* fs.readFile(file, "utf8", function(err, data) {
* if (err) return calback(err);
* try {
* configs[key] = JSON.parse(data);
* } catch (e) {
* return callback(e);
* }
* callback();
* });
* }
*
* // Using callbacks
* async.forEachOf(validConfigFileMap, parseFile, function (err) {
* if (err) {
* console.error(err);
* } else {
* console.log(configs);
* // configs is now a map of JSON data, e.g.
* // { dev: //parsed dev.json, test: //parsed test.json, prod: //parsed prod.json}
* }
* });
*
* //Error handing
* async.forEachOf(invalidConfigFileMap, parseFile, function (err) {
* if (err) {
* console.error(err);
* // JSON parse error exception
* } else {
* console.log(configs);
* }
* });
*
* // Using Promises
* async.forEachOf(validConfigFileMap, parseFile)
* .then( () => {
* console.log(configs);
* // configs is now a map of JSON data, e.g.
* // { dev: //parsed dev.json, test: //parsed test.json, prod: //parsed prod.json}
* }).catch( err => {
* console.error(err);
* });
*
* //Error handing
* async.forEachOf(invalidConfigFileMap, parseFile)
* .then( () => {
* console.log(configs);
* }).catch( err => {
* console.error(err);
* // JSON parse error exception
* });
*
* // Using async/await
* async () => {
* try {
* let result = await async.forEachOf(validConfigFileMap, parseFile);
* console.log(configs);
* // configs is now a map of JSON data, e.g.
* // { dev: //parsed dev.json, test: //parsed test.json, prod: //parsed prod.json}
* }
* catch (err) {
* console.log(err);
* }
* }
*
* //Error handing
* async () => {
* try {
* let result = await async.forEachOf(invalidConfigFileMap, parseFile);
* console.log(configs);
* }
* catch (err) {
* console.log(err);
* // JSON parse error exception
* }
* }
*
*/
function eachOf(coll, iteratee, callback) {
var eachOfImplementation = isArrayLike(coll) ? eachOfArrayLike : eachOfGeneric;
return eachOfImplementation(coll, wrapAsync(iteratee), callback);
}
var eachOf$1 = awaitify(eachOf, 3);
/**
* Produces a new collection of values by mapping each value in `coll` through
* the `iteratee` function. The `iteratee` is called with an item from `coll`
* and a callback for when it has finished processing. Each of these callbacks
* takes 2 arguments: an `error`, and the transformed item from `coll`. If
* `iteratee` passes an error to its callback, the main `callback` (for the
* `map` function) is immediately called with the error.
*
* Note, that since this function applies the `iteratee` to each item in
* parallel, there is no guarantee that the `iteratee` functions will complete
* in order. However, the results array will be in the same order as the
* original `coll`.
*
* If `map` is passed an Object, the results will be an Array. The results
* will roughly be in the order of the original Objects' keys (but this can
* vary across JavaScript engines).
*
* @name map
* @static
* @memberOf module:Collections
* @method
* @category Collection
* @param {Array|Iterable|AsyncIterable|Object} coll - A collection to iterate over.
* @param {AsyncFunction} iteratee - An async function to apply to each item in
* `coll`.
* The iteratee should complete with the transformed item.
* Invoked with (item, callback).
* @param {Function} [callback] - A callback which is called when all `iteratee`
* functions have finished, or an error occurs. Results is an Array of the
* transformed items from the `coll`. Invoked with (err, results).
* @returns {Promise} a promise, if no callback is passed
* @example
*
* // file1.txt is a file that is 1000 bytes in size
* // file2.txt is a file that is 2000 bytes in size
* // file3.txt is a file that is 3000 bytes in size
* // file4.txt does not exist
*
* const fileList = ['file1.txt','file2.txt','file3.txt'];
* const withMissingFileList = ['file1.txt','file2.txt','file4.txt'];
*
* // asynchronous function that returns the file size in bytes
* function getFileSizeInBytes(file, callback) {
* fs.stat(file, function(err, stat) {
* if (err) {
* return callback(err);
* }
* callback(null, stat.size);
* });
* }
*
* // Using callbacks
* async.map(fileList, getFileSizeInBytes, function(err, results) {
* if (err) {
* console.log(err);
* } else {
* console.log(results);
* // results is now an array of the file size in bytes for each file, e.g.
* // [ 1000, 2000, 3000]
* }
* });
*
* // Error Handling
* async.map(withMissingFileList, getFileSizeInBytes, function(err, results) {
* if (err) {
* console.log(err);
* // [ Error: ENOENT: no such file or directory ]
* } else {
* console.log(results);
* }
* });
*
* // Using Promises
* async.map(fileList, getFileSizeInBytes)
* .then( results => {
* console.log(results);
* // results is now an array of the file size in bytes for each file, e.g.
* // [ 1000, 2000, 3000]
* }).catch( err => {
* console.log(err);
* });
*
* // Error Handling
* async.map(withMissingFileList, getFileSizeInBytes)
* .then( results => {
* console.log(results);
* }).catch( err => {
* console.log(err);
* // [ Error: ENOENT: no such file or directory ]
* });
*
* // Using async/await
* async () => {
* try {
* let results = await async.map(fileList, getFileSizeInBytes);
* console.log(results);
* // results is now an array of the file size in bytes for each file, e.g.
* // [ 1000, 2000, 3000]
* }
* catch (err) {
* console.log(err);
* }
* }
*
* // Error Handling
* async () => {
* try {
* let results = await async.map(withMissingFileList, getFileSizeInBytes);
* console.log(results);
* }
* catch (err) {
* console.log(err);
* // [ Error: ENOENT: no such file or directory ]
* }
* }
*
*/
function map (coll, iteratee, callback) {
return _asyncMap(eachOf$1, coll, iteratee, callback)
}
var map$1 = awaitify(map, 3);
/**
* Applies the provided arguments to each function in the array, calling
* `callback` after all functions have completed. If you only provide the first
* argument, `fns`, then it will return a function which lets you pass in the
* arguments as if it were a single function call. If more arguments are
* provided, `callback` is required while `args` is still optional. The results
* for each of the applied async functions are passed to the final callback
* as an array.
*
* @name applyEach
* @static
* @memberOf module:ControlFlow
* @method
* @category Control Flow
* @param {Array|Iterable|AsyncIterable|Object} fns - A collection of {@link AsyncFunction}s
* to all call with the same arguments
* @param {...*} [args] - any number of separate arguments to pass to the
* function.
* @param {Function} [callback] - the final argument should be the callback,
* called when all functions have completed processing.
* @returns {AsyncFunction} - Returns a function that takes no args other than
* an optional callback, that is the result of applying the `args` to each
* of the functions.
* @example
*
* const appliedFn = async.applyEach([enableSearch, updateSchema], 'bucket')
*
* appliedFn((err, results) => {
* // results[0] is the results for `enableSearch`
* // results[1] is the results for `updateSchema`
* });
*
* // partial application example:
* async.each(
* buckets,
* async (bucket) => async.applyEach([enableSearch, updateSchema], bucket)(),
* callback
* );
*/
var applyEach = applyEach$1(map$1);
/**
* The same as [`eachOf`]{@link module:Collections.eachOf} but runs only a single async operation at a time.
*
* @name eachOfSeries
* @static
* @memberOf module:Collections
* @method
* @see [async.eachOf]{@link module:Collections.eachOf}
* @alias forEachOfSeries
* @category Collection
* @param {Array|Iterable|AsyncIterable|Object} coll - A collection to iterate over.
* @param {AsyncFunction} iteratee - An async function to apply to each item in
* `coll`.
* Invoked with (item, key, callback).
* @param {Function} [callback] - A callback which is called when all `iteratee`
* functions have finished, or an error occurs. Invoked with (err).
* @returns {Promise} a promise, if a callback is omitted
*/
function eachOfSeries(coll, iteratee, callback) {
return eachOfLimit$1(coll, 1, iteratee, callback)
}
var eachOfSeries$1 = awaitify(eachOfSeries, 3);
/**
* The same as [`map`]{@link module:Collections.map} but runs only a single async operation at a time.
*
* @name mapSeries
* @static
* @memberOf module:Collections
* @method
* @see [async.map]{@link module:Collections.map}
* @category Collection
* @param {Array|Iterable|AsyncIterable|Object} coll - A collection to iterate over.
* @param {AsyncFunction} iteratee - An async function to apply to each item in
* `coll`.
* The iteratee should complete with the transformed item.
* Invoked with (item, callback).
* @param {Function} [callback] - A callback which is called when all `iteratee`
* functions have finished, or an error occurs. Results is an array of the
* transformed items from the `coll`. Invoked with (err, results).
* @returns {Promise} a promise, if no callback is passed
*/
function mapSeries (coll, iteratee, callback) {
return _asyncMap(eachOfSeries$1, coll, iteratee, callback)
}
var mapSeries$1 = awaitify(mapSeries, 3);
/**
* The same as [`applyEach`]{@link module:ControlFlow.applyEach} but runs only a single async operation at a time.
*
* @name applyEachSeries
* @static
* @memberOf module:ControlFlow
* @method
* @see [async.applyEach]{@link module:ControlFlow.applyEach}
* @category Control Flow
* @param {Array|Iterable|AsyncIterable|Object} fns - A collection of {@link AsyncFunction}s to all
* call with the same arguments
* @param {...*} [args] - any number of separate arguments to pass to the
* function.
* @param {Function} [callback] - the final argument should be the callback,
* called when all functions have completed processing.
* @returns {AsyncFunction} - A function, that when called, is the result of
* appling the `args` to the list of functions. It takes no args, other than
* a callback.
*/
var applyEachSeries = applyEach$1(mapSeries$1);
const PROMISE_SYMBOL = Symbol('promiseCallback');
function promiseCallback () {
let resolve, reject;
function callback (err, ...args) {
if (err) return reject(err)
resolve(args.length > 1 ? args : args[0]);
}
callback[PROMISE_SYMBOL] = new Promise((res, rej) => {
resolve = res,
reject = rej;
});
return callback
}
/**
* Determines the best order for running the {@link AsyncFunction}s in `tasks`, based on
* their requirements. Each function can optionally depend on other functions
* being completed first, and each function is run as soon as its requirements
* are satisfied.
*
* If any of the {@link AsyncFunction}s pass an error to their callback, the `auto` sequence
* will stop. Further tasks will not execute (so any other functions depending
* on it will not run), and the main `callback` is immediately called with the
* error.
*
* {@link AsyncFunction}s also receive an object containing the results of functions which
* have completed so far as the first argument, if they have dependencies. If a
* task function has no dependencies, it will only be passed a callback.
*
* @name auto
* @static
* @memberOf module:ControlFlow
* @method
* @category Control Flow
* @param {Object} tasks - An object. Each of its properties is either a
* function or an array of requirements, with the {@link AsyncFunction} itself the last item
* in the array. The object's key of a property serves as the name of the task
* defined by that property, i.e. can be used when specifying requirements for
* other tasks. The function receives one or two arguments:
* * a `results` object, containing the results of the previously executed
* functions, only passed if the task has any dependencies,
* * a `callback(err, result)` function, which must be called when finished,
* passing an `error` (which can be `null`) and the result of the function's
* execution.
* @param {number} [concurrency=Infinity] - An optional `integer` for
* determining the maximum number of tasks that can be run in parallel. By
* default, as many as possible.
* @param {Function} [callback] - An optional callback which is called when all
* the tasks have been completed. It receives the `err` argument if any `tasks`
* pass an error to their callback. Results are always returned; however, if an
* error occurs, no further `tasks` will be performed, and the results object
* will only contain partial results. Invoked with (err, results).
* @returns {Promise} a promise, if a callback is not passed
* @example
*
* //Using Callbacks
* async.auto({
* get_data: function(callback) {
* // async code to get some data
* callback(null, 'data', 'converted to array');
* },
* make_folder: function(callback) {
* // async code to create a directory to store a file in
* // this is run at the same time as getting the data
* callback(null, 'folder');
* },
* write_file: ['get_data', 'make_folder', function(results, callback) {
* // once there is some data and the directory exists,
* // write the data to a file in the directory
* callback(null, 'filename');
* }],
* email_link: ['write_file', function(results, callback) {
* // once the file is written let's email a link to it...
* callback(null, {'file':results.write_file, 'email':'user@example.com'});
* }]
* }, function(err, results) {
* if (err) {
* console.log('err = ', err);
* }
* console.log('results = ', results);
* // results = {
* // get_data: ['data', 'converted to array']
* // make_folder; 'folder',
* // write_file: 'filename'
* // email_link: { file: 'filename', email: 'user@example.com' }
* // }
* });
*
* //Using Promises
* async.auto({
* get_data: function(callback) {
* console.log('in get_data');
* // async code to get some data
* callback(null, 'data', 'converted to array');
* },
* make_folder: function(callback) {
* console.log('in make_folder');
* // async code to create a directory to store a file in
* // this is run at the same time as getting the data
* callback(null, 'folder');
* },
* write_file: ['get_data', 'make_folder', function(results, callback) {
* // once there is some data and the directory exists,
* // write the data to a file in the directory
* callback(null, 'filename');
* }],
* email_link: ['write_file', function(results, callback) {
* // once the file is written let's email a link to it...
* callback(null, {'file':results.write_file, 'email':'user@example.com'});
* }]
* }).then(results => {
* console.log('results = ', results);
* // results = {
* // get_data: ['data', 'converted to array']
* // make_folder; 'folder',
* // write_file: 'filename'
* // email_link: { file: 'filename', email: 'user@example.com' }
* // }
* }).catch(err => {
* console.log('err = ', err);
* });
*
* //Using async/await
* async () => {
* try {
* let results = await async.auto({
* get_data: function(callback) {
* // async code to get some data
* callback(null, 'data', 'converted to array');
* },
* make_folder: function(callback) {
* // async code to create a directory to store a file in
* // this is run at the same time as getting the data
* callback(null, 'folder');
* },
* write_file: ['get_data', 'make_folder', function(results, callback) {
* // once there is some data and the directory exists,
* // write the data to a file in the directory
* callback(null, 'filename');
* }],
* email_link: ['write_file', function(results, callback) {
* // once the file is written let's email a link to it...
* callback(null, {'file':results.write_file, 'email':'user@example.com'});
* }]
* });
* console.log('results = ', results);
* // results = {
* // get_data: ['data', 'converted to array']
* // make_folder; 'folder',
* // write_file: 'filename'
* // email_link: { file: 'filename', email: 'user@example.com' }
* // }
* }
* catch (err) {
* console.log(err);
* }
* }
*
*/
function auto(tasks, concurrency, callback) {
if (typeof concurrency !== 'number') {
// concurrency is optional, shift the args.
callback = concurrency;
concurrency = null;
}
callback = once(callback || promiseCallback());
var numTasks = Object.keys(tasks).length;
if (!numTasks) {
return callback(null);
}
if (!concurrency) {
concurrency = numTasks;
}
var results = {};
var runningTasks = 0;
var canceled = false;
var hasError = false;
var listeners = Object.create(null);
var readyTasks = [];
// for cycle detection:
var readyToCheck = []; // tasks that have been identified as reachable
// without the possibility of returning to an ancestor task
var uncheckedDependencies = {};
Object.keys(tasks).forEach(key => {
var task = tasks[key];
if (!Array.isArray(task)) {
// no dependencies
enqueueTask(key, [task]);
readyToCheck.push(key);
return;
}
var dependencies = task.slice(0, task.length - 1);
var remainingDependencies = dependencies.length;
if (remainingDependencies === 0) {
enqueueTask(key, task);
readyToCheck.push(key);
return;
}
uncheckedDependencies[key] = remainingDependencies;
dependencies.forEach(dependencyName => {
if (!tasks[dependencyName]) {
throw new Error('async.auto task `' + key +
'` has a non-existent dependency `' +
dependencyName + '` in ' +
dependencies.join(', '));
}
addListener(dependencyName, () => {
remainingDependencies--;
if (remainingDependencies === 0) {
enqueueTask(key, task);
}
});
});
});
checkForDeadlocks();
processQueue();
function enqueueTask(key, task) {
readyTasks.push(() => runTask(key, task));
}
function processQueue() {
if (canceled) return
if (readyTasks.length === 0 && runningTasks === 0) {
return callback(null, results);
}
while(readyTasks.length && runningTasks < concurrency) {
var run = readyTasks.shift();
run();
}
}
function addListener(taskName, fn) {
var taskListeners = listeners[taskName];
if (!taskListeners) {
taskListeners = listeners[taskName] = [];
}
taskListeners.push(fn);
}
function taskComplete(taskName) {
var taskListeners = listeners[taskName] || [];
taskListeners.forEach(fn => fn());
processQueue();
}
function runTask(key, task) {
if (hasError) return;
var taskCallback = onlyOnce((err, ...result) => {
runningTasks--;
if (err === false) {
canceled = true;
return
}
if (result.length < 2) {
[result] = result;
}
if (err) {
var safeResults = {};
Object.keys(results).forEach(rkey => {
safeResults[rkey] = results[rkey];
});
safeResults[key] = result;
hasError = true;
listeners = Object.create(null);
if (canceled) return
callback(err, safeResults);
} else {
results[key] = result;
taskComplete(key);
}
});
runningTasks++;
var taskFn = wrapAsync(task[task.length - 1]);
if (task.length > 1) {
taskFn(results, taskCallback);
} else {
taskFn(taskCallback);
}
}
function checkForDeadlocks() {
// Kahn's algorithm
// https://en.wikipedia.org/wiki/Topological_sorting#Kahn.27s_algorithm
// http://connalle.blogspot.com/2013/10/topological-sortingkahn-algorithm.html
var currentTask;
var counter = 0;
while (readyToCheck.length) {
currentTask = readyToCheck.pop();
counter++;
getDependents(currentTask).forEach(dependent => {
if (--uncheckedDependencies[dependent] === 0) {
readyToCheck.push(dependent);
}
});
}
if (counter !== numTasks) {
throw new Error(
'async.auto cannot execute tasks due to a recursive dependency'
);
}
}
function getDependents(taskName) {
var result = [];
Object.keys(tasks).forEach(key => {
const task = tasks[key];
if (Array.isArray(task) && task.indexOf(taskName) >= 0) {
result.push(key);
}
});
return result;
}
return callback[PROMISE_SYMBOL]
}
var FN_ARGS = /^(?:async\s)?(?:function)?\s*(?:\w+\s*)?\(([^)]+)\)(?:\s*{)/;
var ARROW_FN_ARGS = /^(?:async\s)?\s*(?:\(\s*)?((?:[^)=\s]\s*)*)(?:\)\s*)?=>/;
var FN_ARG_SPLIT = /,/;
var FN_ARG = /(=.+)?(\s*)$/;
function stripComments(string) {
let stripped = '';
let index = 0;
let endBlockComment = string.indexOf('*/');
while (index < string.length) {
if (string[index] === '/' && string[index+1] === '/') {
// inline comment
let endIndex = string.indexOf('\n', index);
index = (endIndex === -1) ? string.length : endIndex;
} else if ((endBlockComment !== -1) && (string[index] === '/') && (string[index+1] === '*')) {
// block comment
let endIndex = string.indexOf('*/', index);
if (endIndex !== -1) {
index = endIndex + 2;
endBlockComment = string.indexOf('*/', index);
} else {
stripped += string[index];
index++;
}
} else {
stripped += string[index];
index++;
}
}
return stripped;
}
function parseParams(func) {
const src = stripComments(func.toString());
let match = src.match(FN_ARGS);
if (!match) {
match = src.match(ARROW_FN_ARGS);
}
if (!match) throw new Error('could not parse args in autoInject\nSource:\n' + src)
let [, args] = match;
return args
.replace(/\s/g, '')
.split(FN_ARG_SPLIT)
.map((arg) => arg.replace(FN_ARG, '').trim());
}
/**
* A dependency-injected version of the [async.auto]{@link module:ControlFlow.auto} function. Dependent
* tasks are specified as parameters to the function, after the usual callback
* parameter, with the parameter names matching the names of the tasks it
* depends on. This can provide even more readable task graphs which can be
* easier to maintain.
*
* If a final callback is specified, the task results are similarly injected,
* specified as named parameters after the initial error parameter.
*
* The autoInject function is purely syntactic sugar and its semantics are
* otherwise equivalent to [async.auto]{@link module:ControlFlow.auto}.
*
* @name autoInject
* @static
* @memberOf module:ControlFlow
* @method
* @see [async.auto]{@link module:ControlFlow.auto}
* @category Control Flow
* @param {Object} tasks - An object, each of whose properties is an {@link AsyncFunction} of
* the form 'func([dependencies...], callback). The object's key of a property
* serves as the name of the task defined by that property, i.e. can be used
* when specifying requirements for other tasks.
* * The `callback` parameter is a `callback(err, result)` which must be called
* when finished, passing an `error` (which can be `null`) and the result of
* the function's execution. The remaining parameters name other tasks on
* which the task is dependent, and the results from those tasks are the
* arguments of those parameters.
* @param {Function} [callback] - An optional callback which is called when all
* the tasks have been completed. It receives the `err` argument if any `tasks`
* pass an error to their callback, and a `results` object with any completed
* task results, similar to `auto`.
* @returns {Promise} a promise, if no callback is passed
* @example
*
* // The example from `auto` can be rewritten as follows:
* async.autoInject({
* get_data: function(callback) {
* // async code to get some data
* callback(null, 'data', 'converted to array');
* },
* make_folder: function(callback) {
* // async code to create a directory to store a file in
* // this is run at the same time as getting the data
* callback(null, 'folder');
* },
* write_file: function(get_data, make_folder, callback) {
* // once there is some data and the directory exists,
* // write the data to a file in the directory
* callback(null, 'filename');
* },
* email_link: function(write_file, callback) {
* // once the file is written let's email a link to it...
* // write_file contains the filename returned by write_file.
* callback(null, {'file':write_file, 'email':'user@example.com'});
* }
* }, function(err, results) {
* console.log('err = ', err);
* console.log('email_link = ', results.email_link);
* });
*
* // If you are using a JS minifier that mangles parameter names, `autoInject`
* // will not work with plain functions, since the parameter names will be
* // collapsed to a single letter identifier. To work around this, you can
* // explicitly specify the names of the parameters your task function needs
* // in an array, similar to Angular.js dependency injection.
*
* // This still has an advantage over plain `auto`, since the results a task
* // depends on are still spread into arguments.
* async.autoInject({
* //...
* write_file: ['get_data', 'make_folder', function(get_data, make_folder, callback) {
* callback(null, 'filename');
* }],
* email_link: ['write_file', function(write_file, callback) {
* callback(null, {'file':write_file, 'email':'user@example.com'});
* }]
* //...
* }, function(err, results) {
* console.log('err = ', err);
* console.log('email_link = ', results.email_link);
* });
*/
function autoInject(tasks, callback) {
var newTasks = {};
Object.keys(tasks).forEach(key => {
var taskFn = tasks[key];
var params;
var fnIsAsync = isAsync(taskFn);
var hasNoDeps =
(!fnIsAsync && taskFn.length === 1) ||
(fnIsAsync && taskFn.length === 0);
if (Array.isArray(taskFn)) {
params = [...taskFn];
taskFn = params.pop();
newTasks[key] = params.concat(params.length > 0 ? newTask : taskFn);
} else if (hasNoDeps) {
// no dependencies, use the function as-is
newTasks[key] = taskFn;
} else {
params = parseParams(taskFn);
if ((taskFn.length === 0 && !fnIsAsync) && params.length === 0) {
throw new Error("autoInject task functions require explicit parameters.");
}
// remove callback param
if (!fnIsAsync) params.pop();
newTasks[key] = params.concat(newTask);
}
function newTask(results, taskCb) {
var newAr