undertaker

Task registry that allows composition through series/parallel methods.

Usage

var fs = require('fs');
var Undertaker = require('undertaker');

var taker = new Undertaker();

taker.task('task1', function(cb){
  // do things

  cb(); // when everything is done
});

taker.task('task2', function(){
  return fs.createReadStream('./myFile.js')
    .pipe(fs.createWriteStream('./myFile.copy.js'));
});

taker.task('task3', function(){
  return new Promise(function(resolve, reject){
    // do things

    resolve(); // when everything is done
  });
});

taker.task('combined', taker.series('task1', 'task2'));

taker.task('all', taker.parallel('combined', 'task3'));

API

Task functions can be completed in any of the ways supported by async-done

`new Undertaker([registryInstance])`

The constructor is used to create a new instance of Undertaker. Each instance of Undertaker gets its own instance of a registry. By default, the registry is an instance of undertaker-registry but it can be an instance of any other registry that follows the Custom Registries API.

To use a custom registry, pass a custom registry instance (new CustomRegistry([options])) when instantiating a new Undertaker instance. This will use the custom registry instance for that Undertaker instance.

`task([taskName,] fn)`

Both a getter and setter for tasks.

If a string (taskName) is given as the only argument, it behaves as a getter and returns the wrapped task (not the original function). The wrapped task has a unwrap method that will return the original function.

If a function (fn) and optionally a string (taskName) is given, it behaves as a setter and will register the task by the taskName. If taskName is not specified, the name or displayName property of the function is used as the taskName.

Will throw if:

As a getter: taskName is missing or not a string.
As a setter: taskName is missing and fn is anonymous.
As a setter: fn is missing or not a function.

`series(taskName || fn...)`

Takes a variable amount of strings (taskName) and/or functions (fn) and returns a function of the composed tasks or functions. Any taskNames are retrieved from the registry using the get method.

When the returned function is executed, the tasks or functions will be executed in series, each waiting for the prior to finish. If an error occurs, execution will stop.

`parallel(taskName || fn...)`

When the returned function is executed, the tasks or functions will be executed in parallel, all being executed at the same time. If an error occurs, all execution will complete.

`registry([registryInstance])`

Optionally takes an instantiated registry object. If no arguments are passed, returns the current registry object. If an instance of a registry (customRegistry) is passed the tasks from the current registry will be transferred to it and the current registry will be replaced with the new registry.

The ability to assign new registries will allow you to pre-define/share tasks or add custom functionality to your registries. See Custom Registries for more information.

`tree([options])`

Optionally takes an options object and returns an object representing the tree of registered tasks. The object returned is archy compatible. Also, each node has a type property that can be used to determine if the node is a task or function.

`options`

`options.deep`

Whether or not the whole tree should be returned.

Type: Boolean

Default: false

`lastRun(task, [precision])`

Takes a string or function (task) and returns a timestamp of the last time the task was run successfully. The time will be the time the task started.

Returns undefined if the task has not been run.

If a task errors, the result of lastRun will be undefined because the task should probably be re-run from scratch to get into a good state again.

The timestamp is always given in millisecond but the time resolution can be rounded using the precision parameter. The use case is to be able to compare a build time to a file time attribute.

Assuming undertakerInst.lastRun('someTask') returns 1426000001111, undertakerInst.lastRun('someTask', 1000) returns 1426000001000.

The default time resolution is 1.

Custom Registries

Custom registries are constructor functions allowing you to pre-define/share tasks or add custom functionality to your registries.

A registry's prototype should define:

init(taker): receives the undertaker instance to set pre-defined tasks using the task(taskName, fn) method.
get(taskName): returns the task with that name or undefined if no task is registered with that name.
set(taskName, fn): add task to the registry. If set modifies a task, it should return the new task.
tasks(): returns an object listing all tasks in the registry.

You should not call these functions yourself; leave that to Undertaker, so it can keep its metadata consistent.

The easiest way to create a custom registry is to inherit from undertaker-registry:

var util = require('util');

var DefaultRegistry = require('undertaker-registry');

function MyRegistry(){
  DefaultRegistry.call(this);
}

util.inherits(MyRegistry, DefaultRegistry);

module.exports = MyRegistry;

Sharing tasks

To share common tasks with all your projects, you can expose an init method on the registry prototype and it will receive the Undertaker instance as the only argument. You can then use undertaker.task(name, fn) to register pre-defined tasks.

For example you might want to share a clean task:

var fs = require('fs');
var util = require('util');

var DefaultRegistry = require('undertaker-registry');
var del = require('del');

function CommonRegistry(opts){
  DefaultRegistry.call(this);

  opts = opts || {};

  this.buildDir = opts.buildDir || './build';
}

util.inherits(CommonRegistry, DefaultRegistry);

CommonRegistry.prototype.init = function(takerInst){
  var buildDir = this.buildDir;
  var exists = fs.existsSync(buildDir);

  if(exists){
    throw new Error('Cannot initialize common tasks. ' + buildDir + ' directory exists.');
  }

  takerInst.task('clean', function(){
    return del([buildDir]);
  });
}

module.exports = CommonRegistry;

Then to use it in a project:

var Undertaker = require('undertaker');
var CommonRegistry = require('myorg-common-tasks');

var taker = new Undertaker(CommonRegistry({ buildDir: '/dist' }));

taker.task('build', taker.series('clean', function build(cb) {
  // do things
  cb();
}));

Sharing Functionalities

By controlling how tasks are added to the registry, you can decorate them.

For example if you wanted all tasks to share some data, you can use a custom registry to bind them to that data. Be sure to return the altered task, as per the description of registry methods above:

var util = require('util');

var Undertaker = require('undertaker');
var DefaultRegistry = require('undertaker-registry');

// Some task defined somewhere else
var BuildRegistry = require('./build.js');
var ServeRegistry = require('./serve.js');

function ConfigRegistry(config){
  DefaultRegistry.call(this);
  this.config = config;
}

util.inherits(ConfigRegistry, DefaultRegistry);

ConfigRegistry.prototype.set = function set(name, fn) {
  // The `DefaultRegistry` uses `this._tasks` for storage.
  var task = this._tasks[name] = fn.bind(this.config);
  return task;
};

var taker = new Undertaker();

taker.registry(new BuildRegistry());
taker.registry(new ServeRegistry());

// `taker.registry` will reset each task in the registry with
// `ConfigRegistry.prototype.set` which will bind them to the config object.
taker.registry(new ConfigRegistry({
  src: './src',
  build: './build',
  bindTo: '0.0.0.0:8888'
}));

taker.task('default', taker.series('clean', 'build', 'serve', function(cb) {
  console.log('Server bind to ' + this.bindTo);
  console.log('Serving' + this.build);
  cb();
}));

In the wild

undertaker-registry - Custom registries probably want to inherit from this.
undertaker-forward-reference - Custom registry supporting forward referenced tasks (similar to gulp 3.x).
undertaker-task-metadata - Proof-of-concept custom registry that attaches metadata to each task.
undertaker-common-tasks - Proof-of-concept custom registry that pre-defines some tasks.
alchemist-gulp - A default set of tasks for building alchemist plugins.
gulp-hub - Custom registry to run tasks in multiple gulpfiles. (In a branch as of this writing)
gulp-pipeline - RailsRegistry is an ES2015 class that provides a gulp pipeline replacement for rails applications