import once from './internal/once'; import onlyOnce from './internal/onlyOnce'; import wrapAsync from './internal/wrapAsync'; import { promiseCallback, PROMISE_SYMBOL } from './internal/promiseCallback' /** * 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); * } * } * */ export default 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] }