Just

Just is a build task definition library. It stands on the shoulders of two excellent and well tested libraries: undertaker and yargs.

Why not just gulp?

undertaker underpins the orchestration layer of gulp. So why not just use gulp? Everyone who uses gulp can related to these pain points:

1. It has a LOT of dependencies
2. gulp-* plugins adds an extra level of abstraction that isn't needed most of the time
3. vinylfs abstraction and streaming content from plugin to plugin is not an intuitive way to code tools
4. gulp has a strange versioning policy where @latest is still at 3.x while 4.0 is stable and released a while ago - this confuses consumers of the library

Core concepts

The core concept of this library is that related tasks are grouped together and exported via npm packages. Each project will have a just-task.js that imports tasks from those packages and also defines custom tasks for the project itself.

For example, the just-task-typescript package is installable from npmjs.org and exports typescript and typescript:watch tasks. A rig file can then import and use them it like this:

require('just-task-typescript');

const { task, series } = require('just-task');

task('clean', function() {
  // do the cleaning task stuff here
});

task('build', series('clean', 'typescript'));

Usage

With the just-task.js in the root of the project, you can run the task by running:

just <task> [arguments]

For example:

just build --production

What types of tasks are available?

Synchronous tasks

While gulp@4 got rid of the capability of having synchronous tasks. just-task augments undertaker to allow this style of task.

task('sync-task', function() {
  this.logger.info('Look ma! A Sync Task!');
});

As you can see, lambda's are NOT supported. This is because the functions are bound to a context for this so the tasks can gain access to just-task-provided things like logger. Another thing that can be accessed from the context is the argv which is parsed by yargs.

Asynchronous tasks with promises

just-task supports asynchronous tasks with promises. Simply return a promise in a task function and just-task will do the right thing.

// Async / Await automatically returns a promise
task('async-task', async function() {
  const response = await fetch('https://google.com');
  const html = await response.text();

  // do something with `html`
});

// Or remember to return a promise to make async tasks work
task('async-task-promise', function() {
  return Promise.resolve('dummy');
});

Asynchronous tasks with callback

There are times when a callback-based async task is desired. There are times when the task is waiting on the completion of an asynchronous procedure from Node.js. Since most long-running Node.js function expects a callback to notify completion, just-task supports this feature.

task('async-task-callback', function(cb) {
  const logger = this.logger;
  fs.readFile('./temp/file.txt', (err, data) => {
    logger.info('file contents: ' + data.toString());
    cb();
  });
});

Contributing

This project welcomes contributions and suggestions. Most contributions require you to agree to a Contributor License Agreement (CLA) declaring that you have the right to, and actually do, grant us the rights to use your contribution. For details, visit https://cla.microsoft.com.

When you submit a pull request, a CLA-bot will automatically determine whether you need to provide a CLA and decorate the PR appropriately (e.g., label, comment). Simply follow the instructions provided by the bot. You will only need to do this once across all repos using our CLA.

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact opencode@microsoft.com with any additional questions or comments.