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import auto from './auto';
import forOwn from 'lodash/forOwn';
import arrayMap from 'lodash/_arrayMap';
import clone from 'lodash/_copyArray';
import isArray from 'lodash/isArray';
var argsRegex = /^function\s*[^\(]*\(\s*([^\)]*)\)/m;
function parseParams(func) {
return func.toString().match(argsRegex)[1].split(/\s*\,\s*/);
}
/**
* A dependency-injected version of the [`auto`](#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 [`auto`](#auto).
*
* @name autoInject
* @static
* @memberOf async
* @see `async.auto`
* @category Control Flow
* @param {Object} tasks - An object, each of whose properties is a function 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. The remaining parameters are task names
* whose results you are interested in. This callback will only be called when
* all tasks have finished or an error has occurred, and so do not specify
* dependencies in the same way as `tasks` do. If an error occurs, no further
* `tasks` will be performed, and `results` will only be valid for those tasks
* which managed to complete. Invoked with (err, [results...]).
* @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, email_link) {
* console.log('err = ', err);
* console.log('email_link = ', 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. The final
* // results callback can be provided as an array in the same way.
*
* // 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'});
* }]
* //...
* }, ['email_link', function(err, email_link) {
* console.log('err = ', err);
* console.log('email_link = ', email_link);
* }]);
*/
export default function autoInject(tasks, callback) {
var newTasks = {};
forOwn(tasks, function (taskFn, key) {
var params;
if (isArray(taskFn)) {
params = clone(taskFn);
taskFn = params.pop();
newTasks[key] = params.concat(newTask);
} else if (taskFn.length === 0) {
throw new Error("autoInject task functions require explicit parameters.");
} else if (taskFn.length === 1) {
// no dependencies, use the function as-is
newTasks[key] = taskFn;
} else {
params = parseParams(taskFn);
params.pop();
newTasks[key] = params.concat(newTask);
}
function newTask(results, taskCb) {
var newArgs = arrayMap(params, function (name) {
return results[name];
});
newArgs.push(taskCb);
taskFn.apply(null, newArgs);
}
});
auto(newTasks, callback);
}
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