333 lines
12 KiB
JavaScript
333 lines
12 KiB
JavaScript
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'use strict';
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Object.defineProperty(exports, "__esModule", {
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value: true
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});
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exports.default = auto;
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var _once = require('./internal/once.js');
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var _once2 = _interopRequireDefault(_once);
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var _onlyOnce = require('./internal/onlyOnce.js');
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var _onlyOnce2 = _interopRequireDefault(_onlyOnce);
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var _wrapAsync = require('./internal/wrapAsync.js');
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var _wrapAsync2 = _interopRequireDefault(_wrapAsync);
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var _promiseCallback = require('./internal/promiseCallback.js');
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function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
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/**
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* Determines the best order for running the {@link AsyncFunction}s in `tasks`, based on
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* their requirements. Each function can optionally depend on other functions
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* being completed first, and each function is run as soon as its requirements
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* are satisfied.
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*
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* If any of the {@link AsyncFunction}s pass an error to their callback, the `auto` sequence
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* will stop. Further tasks will not execute (so any other functions depending
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* on it will not run), and the main `callback` is immediately called with the
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* error.
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*
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* {@link AsyncFunction}s also receive an object containing the results of functions which
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* have completed so far as the first argument, if they have dependencies. If a
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* task function has no dependencies, it will only be passed a callback.
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*
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* @name auto
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* @static
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* @memberOf module:ControlFlow
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* @method
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* @category Control Flow
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* @param {Object} tasks - An object. Each of its properties is either a
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* function or an array of requirements, with the {@link AsyncFunction} itself the last item
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* in the array. The object's key of a property serves as the name of the task
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* defined by that property, i.e. can be used when specifying requirements for
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* other tasks. The function receives one or two arguments:
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* * a `results` object, containing the results of the previously executed
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* functions, only passed if the task has any dependencies,
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* * a `callback(err, result)` function, which must be called when finished,
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* passing an `error` (which can be `null`) and the result of the function's
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* execution.
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* @param {number} [concurrency=Infinity] - An optional `integer` for
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* determining the maximum number of tasks that can be run in parallel. By
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* default, as many as possible.
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* @param {Function} [callback] - An optional callback which is called when all
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* the tasks have been completed. It receives the `err` argument if any `tasks`
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* pass an error to their callback. Results are always returned; however, if an
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* error occurs, no further `tasks` will be performed, and the results object
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* will only contain partial results. Invoked with (err, results).
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* @returns {Promise} a promise, if a callback is not passed
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* @example
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*
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* //Using Callbacks
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* async.auto({
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* get_data: function(callback) {
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* // async code to get some data
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* callback(null, 'data', 'converted to array');
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* },
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* make_folder: function(callback) {
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* // async code to create a directory to store a file in
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* // this is run at the same time as getting the data
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* callback(null, 'folder');
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* },
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* write_file: ['get_data', 'make_folder', function(results, callback) {
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* // once there is some data and the directory exists,
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* // write the data to a file in the directory
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* callback(null, 'filename');
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* }],
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* email_link: ['write_file', function(results, callback) {
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* // once the file is written let's email a link to it...
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* callback(null, {'file':results.write_file, 'email':'user@example.com'});
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* }]
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* }, function(err, results) {
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* if (err) {
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* console.log('err = ', err);
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* }
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* console.log('results = ', results);
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* // results = {
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* // get_data: ['data', 'converted to array']
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* // make_folder; 'folder',
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* // write_file: 'filename'
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* // email_link: { file: 'filename', email: 'user@example.com' }
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* // }
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* });
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*
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* //Using Promises
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* async.auto({
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* get_data: function(callback) {
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* console.log('in get_data');
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* // async code to get some data
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* callback(null, 'data', 'converted to array');
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* },
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* make_folder: function(callback) {
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* console.log('in make_folder');
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* // async code to create a directory to store a file in
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* // this is run at the same time as getting the data
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* callback(null, 'folder');
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* },
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* write_file: ['get_data', 'make_folder', function(results, callback) {
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* // once there is some data and the directory exists,
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* // write the data to a file in the directory
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* callback(null, 'filename');
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* }],
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* email_link: ['write_file', function(results, callback) {
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* // once the file is written let's email a link to it...
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* callback(null, {'file':results.write_file, 'email':'user@example.com'});
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* }]
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* }).then(results => {
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* console.log('results = ', results);
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* // results = {
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* // get_data: ['data', 'converted to array']
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* // make_folder; 'folder',
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* // write_file: 'filename'
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* // email_link: { file: 'filename', email: 'user@example.com' }
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* // }
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* }).catch(err => {
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* console.log('err = ', err);
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* });
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*
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* //Using async/await
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* async () => {
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* try {
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* let results = await async.auto({
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* get_data: function(callback) {
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* // async code to get some data
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* callback(null, 'data', 'converted to array');
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* },
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* make_folder: function(callback) {
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* // async code to create a directory to store a file in
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* // this is run at the same time as getting the data
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* callback(null, 'folder');
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* },
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* write_file: ['get_data', 'make_folder', function(results, callback) {
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* // once there is some data and the directory exists,
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* // write the data to a file in the directory
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* callback(null, 'filename');
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* }],
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* email_link: ['write_file', function(results, callback) {
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* // once the file is written let's email a link to it...
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* callback(null, {'file':results.write_file, 'email':'user@example.com'});
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* }]
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* });
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* console.log('results = ', results);
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* // results = {
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* // get_data: ['data', 'converted to array']
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* // make_folder; 'folder',
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* // write_file: 'filename'
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* // email_link: { file: 'filename', email: 'user@example.com' }
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* // }
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* }
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* catch (err) {
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* console.log(err);
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* }
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* }
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*
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*/
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function auto(tasks, concurrency, callback) {
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if (typeof concurrency !== 'number') {
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// concurrency is optional, shift the args.
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callback = concurrency;
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concurrency = null;
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}
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callback = (0, _once2.default)(callback || (0, _promiseCallback.promiseCallback)());
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var numTasks = Object.keys(tasks).length;
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if (!numTasks) {
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return callback(null);
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}
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if (!concurrency) {
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concurrency = numTasks;
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}
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var results = {};
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var runningTasks = 0;
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var canceled = false;
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var hasError = false;
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var listeners = Object.create(null);
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var readyTasks = [];
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// for cycle detection:
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var readyToCheck = []; // tasks that have been identified as reachable
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// without the possibility of returning to an ancestor task
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var uncheckedDependencies = {};
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Object.keys(tasks).forEach(key => {
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var task = tasks[key];
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if (!Array.isArray(task)) {
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// no dependencies
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enqueueTask(key, [task]);
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readyToCheck.push(key);
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return;
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}
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var dependencies = task.slice(0, task.length - 1);
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var remainingDependencies = dependencies.length;
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if (remainingDependencies === 0) {
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enqueueTask(key, task);
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readyToCheck.push(key);
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return;
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}
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uncheckedDependencies[key] = remainingDependencies;
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dependencies.forEach(dependencyName => {
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if (!tasks[dependencyName]) {
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throw new Error('async.auto task `' + key + '` has a non-existent dependency `' + dependencyName + '` in ' + dependencies.join(', '));
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}
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addListener(dependencyName, () => {
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remainingDependencies--;
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if (remainingDependencies === 0) {
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enqueueTask(key, task);
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}
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});
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});
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});
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checkForDeadlocks();
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processQueue();
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function enqueueTask(key, task) {
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readyTasks.push(() => runTask(key, task));
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}
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function processQueue() {
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if (canceled) return;
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if (readyTasks.length === 0 && runningTasks === 0) {
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return callback(null, results);
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}
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while (readyTasks.length && runningTasks < concurrency) {
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var run = readyTasks.shift();
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run();
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}
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}
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function addListener(taskName, fn) {
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var taskListeners = listeners[taskName];
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if (!taskListeners) {
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taskListeners = listeners[taskName] = [];
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}
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taskListeners.push(fn);
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}
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function taskComplete(taskName) {
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var taskListeners = listeners[taskName] || [];
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taskListeners.forEach(fn => fn());
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processQueue();
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}
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function runTask(key, task) {
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if (hasError) return;
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var taskCallback = (0, _onlyOnce2.default)((err, ...result) => {
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runningTasks--;
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if (err === false) {
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canceled = true;
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return;
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}
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if (result.length < 2) {
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[result] = result;
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}
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if (err) {
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var safeResults = {};
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Object.keys(results).forEach(rkey => {
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safeResults[rkey] = results[rkey];
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});
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safeResults[key] = result;
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hasError = true;
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listeners = Object.create(null);
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if (canceled) return;
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callback(err, safeResults);
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} else {
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results[key] = result;
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taskComplete(key);
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}
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});
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runningTasks++;
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var taskFn = (0, _wrapAsync2.default)(task[task.length - 1]);
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if (task.length > 1) {
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taskFn(results, taskCallback);
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} else {
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taskFn(taskCallback);
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}
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}
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function checkForDeadlocks() {
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// Kahn's algorithm
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// https://en.wikipedia.org/wiki/Topological_sorting#Kahn.27s_algorithm
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// http://connalle.blogspot.com/2013/10/topological-sortingkahn-algorithm.html
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var currentTask;
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var counter = 0;
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while (readyToCheck.length) {
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currentTask = readyToCheck.pop();
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counter++;
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getDependents(currentTask).forEach(dependent => {
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if (--uncheckedDependencies[dependent] === 0) {
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readyToCheck.push(dependent);
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}
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});
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}
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if (counter !== numTasks) {
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throw new Error('async.auto cannot execute tasks due to a recursive dependency');
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}
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}
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function getDependents(taskName) {
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var result = [];
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Object.keys(tasks).forEach(key => {
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const task = tasks[key];
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if (Array.isArray(task) && task.indexOf(taskName) >= 0) {
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result.push(key);
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}
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});
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return result;
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}
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return callback[_promiseCallback.PROMISE_SYMBOL];
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}
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module.exports = exports.default;
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