Front-End JS Libraries with Composer

Reposted from the Acquia Lightning site.

In Lightning 2.1.7, we're finally answering a long-standing question: "If I'm managing my code base with Composer, how can I bring front-end JavaScript libraries into my site?"

This has long been a tricky issue. drupal.org doesn't really provide an official solution -- modules that require JavaScript libraries usually include instructions for downloading and extracting said libraries yourself. Libraries API can help in some cases; distributions are allowed to ship certain libraries. But if you're building your site with Composer, you've been more or less on your own.

Now, the Lightning team has decided to add support for Asset Packagist. This useful repository acts as a bridge between Composer and the popular NPM and Bower repositories, which catalog thousands of useful front-end and JavaScript packages. When you have Asset Packagist enabled in a Composer project, you can install a Bower package like this (using Dropzone as an example):

$ composer require bower-asset/dropzone

And you can install an NPM package just as easily:

$ composer require npm-asset/dropzone

To use Asset Packagist in your project, merge the following into your composer.json:

"repositories": [ { "type: "composer", "url": "https://asset-packagist.org" }]

Presto! You can now add Bower and NPM packages to your project as if they were normal PHP packages. Yay! However...

Normally, asset packages will be installed in the vendor directory, like any other Composer package. This probably isn't what you want to do with a front-end JavaScript library, though -- luckily, there is a special plugin you can use to install the libraries in the right place. Note that you'll need Composer 1.5 (recently released) or later for this to work; run composer self-update if you're using an older version of Composer.

Now, add the plugin as a dependency:

$ composer require oomphinc/composer-installers-extender

Then merge the following into your composer.json:

"extra": { "installer-types": [ "bower-asset", "npm-asset" ], "installer-paths": { "path/to/docroot/libraries/{$name}": [ "type:bower-asset", "type:npm-asset" ] }}

Now, when you install a Bower or NPM package, it will be placed in docroot/libraries/NAME_OF_PACKAGE. Boo-yah!

Let's face it -- if you're using Composer to manage your Drupal code base and you want to add some JavaScript libraries, Asset Packagist rocks your socks around the block.

BUT! Note that this -- adding front-end libraries to a browser-based application -- is really the only use case for which Asset Packagist is appropriate. If you're writing a JavaScript app for Node, you should use NPM or Yarn, not Composer! Asset Packagist isn't meant to replace NPM or Bower, and it doesn't necessarily resolve dependencies the same way they do. So use this power wisely and well!

P.S. Lightning 2.1.7 includes a script which can help set up your project's composer.json to use Asset Packagist. To run this script, switch into the Lightning profile directory and run:

$ composer run enable-asset-packagist