composer

Run and compose async tasks. Easily define groups of tasks to run in series or parallel.

Please consider following this project's author, Brian Woodward, and consider starring the project to show your :heart: and support.

• Install
• Usage
• API
  • Tasks
  • Generators
• Events
  • task
  • task-pending
  • task-preparing
• Release history
• About

(TOC generated by verb using markdown-toc)

Install

Install with npm:

$ npm install --save composer

Usage

// Create an instance of `Composer`
const Composer = require('composer');
const composer = new Composer();

// Define tasks with the .task() method
composer.task('foo', callback => {
  callback(); // do stuff
});
composer.task('bar', callback => {
  callback(); // do stuff
});

composer.task('baz', ['foo'. 'bar']);

// Run tasks with the .build() method
composer.build('baz')
  .then(() => console.log('done!'))
  .catch(console.error);

API

.factory

Factory for creating a custom Tasks class that extends the given Emitter. Or, simply call the factory function to use the built-in emitter.

Params

• Emitter {function}: Event emitter.
• returns {Class}: Returns a custom Tasks class.

Example

// custom emitter
const Emitter = require('events');
const Tasks = require('composer/lib/tasks')(Emitter);
// built-in emitter
const Tasks = require('composer/lib/tasks')();
const composer = new Tasks();

Tasks

Create an instance of Tasks with the given options.

Params

• options {object}

Example

const Tasks = require('composer').Tasks;
const composer = new Tasks();

.task

Define a task. Tasks run asynchronously, either in series (by default) or parallel (when options.parallel is true). In order for the build to determine when a task is complete, one of the following things must happen: 1) the callback must be called, 2) a promise must be returned, or 3) a stream must be returned. Inside tasks, the "this" object is a composer Task instance created for each task with useful properties like the task name, options and timing information, which can be useful for logging, etc.

Params

• name {String}: The task name.
• deps {Object|Array|String|Function}: Any of the following: task dependencies, callback(s), or options object, defined in any order.
• callback {Function}: (optional) If the last argument is a function, it will be called after all of the task's dependencies have been run.
• returns {undefined}

Example

// 1. callback
app.task('default', cb => {
  // do stuff
  cb();
});
// 2. promise
app.task('default', () => {
  return Promise.resolve(null);
});
// 3. stream (using vinyl-fs or your stream of choice)
app.task('default', function() {
  return vfs.src('foo/*.js');
});

.build

Run one or more tasks.

Params

• tasks {object|array|string|function}: One or more tasks to run, options, or callback function. If no tasks are defined, the default task is automatically run.
• callback {function}: (optional)
• returns {undefined}

Example

const build = app.series(['foo', 'bar', 'baz']);
// promise
build().then(console.log).catch(console.error);
// or callback
build(function() {
  if (err) return console.error(err);
});

.series

Compose a function to run the given tasks in series.

Params

• tasks {object|array|string|function}: Tasks to run, options, or callback function. If no tasks are defined, the default task is automatically run, if one exists.
• callback {function}: (optional)
• returns {promise|undefined}: Returns a promise if no callback is passed.

Example

const build = app.series(['foo', 'bar', 'baz']);
// promise
build().then(console.log).catch(console.error);
// or callback
build(function() {
  if (err) return console.error(err);
});

.parallel

Compose a function to run the given tasks in parallel.

Params

• tasks {object|array|string|function}: Tasks to run, options, or callback function. If no tasks are defined, the default task is automatically run, if one exists.
• callback {function}: (optional)
• returns {promise|undefined}: Returns a promise if no callback is passed.

Example

// call the returned function to start the build
const build = app.parallel(['foo', 'bar', 'baz']);
// promise
build().then(console.log).catch(console.error);
// callback
build(function() {
  if (err) return console.error(err);
});
// example task usage
app.task('default', build);

.create

Static method for creating a custom Tasks class with the given `Emitter.

Params

• Emitter {Function}
• returns {Class}: Returns the custom class.

.create

Static factory method for creating a custom Composer class that extends the given Emitter.

Params

• Emitter {Function}: Event emitter.
• returns {Class}: Returns a custom Composer class.

Example

// Composer extends a basic event emitter by default
const Composer = require('composer');
const composer = new Composer();

// Create a custom Composer class with your even emitter of choice
const Emitter = require('some-emitter');
const CustomComposer = Composer.create(Emitter);
const composer = new CustomComposer();

Params

• name {String}
• options {Object}
• returns {Object}: Returns an instance of Composer.

Example

const composer = new Composer();

Create a wrapped generator function with the given name, config, and fn.

Params

• name {String}
• config {Object}: (optional)
• fn {Function}
• returns {Function}

Returns true if the given value is a Composer generator object.

Params

• val {Object}
• returns {Boolean}

.register

Alias to .setGenerator.

Params

• name {String}: The generator's name
• options {Object|Function|String}: or generator
• generator {Object|Function|String}: Generator function, instance or filepath.
• returns {Object}: Returns the generator instance.

Example

app.register('foo', function(app, base) {
  // "app" is a private instance created for the generator
  // "base" is a shared instance
});

.generator

Get and invoke generator name, or register generator name with the given val and options, then invoke and return the generator instance. This method differs from .register, which lazily invokes generator functions when .generate is called.

Params

• name {String}
• fn {Function|Object}: Generator function, instance or filepath.
• returns {Object}: Returns the generator instance or undefined if not resolved.

Example

app.generator('foo', function(app, options) {
  // "app" - private instance created for generator "foo"
  // "options" - options passed to the generator
});

.setGenerator

Store a generator by file path or instance with the given name and options.

Params

• name {String}: The generator's name
• options {Object|Function|String}: or generator
• generator {Object|Function|String}: Generator function, instance or filepath.
• returns {Object}: Returns the generator instance.

Example

app.setGenerator('foo', function(app, options) {
  // "app" - new instance of Generator created for generator "foo"
  // "options" - options passed to the generator
});

.getGenerator

Get generator name from app.generators, same as [findGenerator], but also invokes the returned generator with the current instance. Dot-notation may be used for getting sub-generators.

Params

• name {String}: Generator name.
• returns {Object|undefined}: Returns the generator instance or undefined.

Example

const foo = app.getGenerator('foo');

// get a sub-generator
const baz = app.getGenerator('foo.bar.baz');

.findGenerator

Find generator name, by first searching the cache, then searching the cache of the base generator. Use this to get a generator without invoking it.

Params

• name {String}
• options {Function}: Optionally supply a rename function on options.toAlias
• returns {Object|undefined}: Returns the generator instance if found, or undefined.

Example

// search by "alias"
const foo = app.findGenerator('foo');

// search by "full name"
const foo = app.findGenerator('generate-foo');

Params

• name {String}
• returns {Boolean}

Example

console.log(app.hasGenerator('foo'));
console.log(app.hasGenerator('foo.bar'));

.generate

Run one or more tasks or sub-generators and returns a promise.

Params

• name {String}
• tasks {String|Array}
• returns {Promise}

Events

• emits: generate with the generator name and the array of tasks that are queued to run.

Example

// run tasks `bar` and `baz` on generator `foo`
app.generate('foo', ['bar', 'baz']);

// or use shorthand
app.generate('foo:bar,baz');

// run the `default` task on generator `foo`
app.generate('foo');

// run the `default` task on the `default` generator, if defined
app.generate();

.toAlias

Create a generator alias from the given name. By default, generate- is stripped from beginning of the generator name.

Params

• name {String}
• options {Object}
• returns {String}: Returns the alias.

Example

// customize the alias
const app = new Generate({ toAlias: require('camel-case') });

.isGenerators

Returns true if every name in the given array is a registered generator.

Params

• names {Array}
• returns {Boolean}

.formatError

Format task and generator errors.

Params

• name {String}
• returns {Error}

.disableInspect

Disable inspect. Returns a function to re-enable inspect. Useful for debugging.

.base

Get the first ancestor instance of Composer. Only works if generator.parent is defined on child instances.

.name

Get or set the generator name.

Params

• {String}

• returns {String}

.alias

Get or set the generator alias. By default, the generator alias is created by passing the generator name to the .toAlias method.

Params

• {String}

• returns {String}

.namespace

Get the generator namespace. The namespace is created by joining the generator's alias to the alias of each ancestor generator.

Params

• {String}

• returns {String}

.depth

Get the depth of a generator - useful for debugging. The root generator has a depth of 0, sub-generators add 1 for each level of nesting.

• returns {Number}

Composer#parse

Static method that returns a function for parsing task arguments.

Params

• register {Function}: Function that receives a name of a task or generator that cannot be found by the parse function. This allows the register function to dynamically register tasks or generators.
• returns {Function}: Returns a function for parsing task args.

Composer#isGenerator

Static method that returns true if the given val is an instance of Generate.

Params

• val {Object}
• returns {Boolean}

Composer#create

Static method for creating a custom Composer class with the given `Emitter.

Params

• Emitter {Function}
• returns {Class}: Returns the custom class.

Composer#Tasks

Static getter for getting the Tasks class with the same Emitter class as Composer.

Params

• Emitter {Function}
• returns {Class}: Returns the Tasks class.

Composer#Task

Static getter for getting the Task class.

Example

const { Task } = require('composer');

Events

task

app.on('task', function(task) {
  switch (task.status) {
    case 'starting':
      // Task is running
      break;
    case 'finished':
      // Task is finished running
      break;
  }
});

task-pending

Emitted after a task is registered.

task-preparing

Emitted when a task is preparing to run, right before it's called. You can use this event to dynamically skip tasks by updating task.skip to true or a function.

Release history

See the changelog.

About

Pull requests and stars are always welcome. For bugs and feature requests, please create an issue.

Running and reviewing unit tests is a great way to get familiarized with a library and its API. You can install dependencies and run tests with the following command:

$ npm install && npm test

(This project's readme.md is generated by verb, please don't edit the readme directly. Any changes to the readme must be made in the .verb.md readme template.)

To generate the readme, run the following command:

$ npm install -g verbose/verb#dev verb-generate-readme && verb

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Contributors

| Commits | Contributor |
| --- | --- |
| 227 | doowb |
| 72 | jonschlinkert |

Author

Brian Woodward

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• LinkedIn Profile

License

Copyright © 2018, Brian Woodward. Released under the MIT License.

This file was generated by verb-generate-readme, v0.8.0, on November 11, 2018.