Composing with Composer Manager

Why Composer?

We at Savas Labs love Composer and use it with many of our projects to help manage our automated testing dependencies.

For those not already familiar, Composer is a package manager for PHP. If you want to go further down the rabbit hole “a package is a namespace that organizes a set of related classes and interfaces.”

Basically, Composer allows you to manage dependencies on a per project basis. Those dependencies live within the project directory so that everything is encapsulated there. And since you can specify package versions, different projects on your systems can depend on different versions. Composer also pulls in the dependencies of your project’s dependencies, keeping you out of ‘dependency hell’. You simply specify your projects dependencies in a composer.json file, then pull in all of your project’s dependencies into a /vendor directory on the command line via composer install. (You can also update your dependencies via composer update).

Composer with Drupal Modules?

But recently, one of our projects required a custom module that depended on a PHP package that expected to be installed via Composer.

While we were excited that we could use Composer to easily install the dependency, we hadn’t used Composer to manage dependencies within a Drupal module before, and this requirement raised a new concern: What if more than one module requires the same package? In that scenario, how do we avoid duplicate code, and more seriously, how do we avoid version conflicts?

Composer Manager to the Rescue!

Things get a little more complex when Drupal modules start specifying dependencies. But luckily for us, Composer Manager thought this through and provides a solution.

Composer Manager is a Drupal contributed module with releases for Drupal 6, 7, and 8. From the project description:

Composer Manager allows each contributed module to ship with its own composer.json file, listing the module-specific requirements. It then merges the requirements of all found modules into the consolidated composer.json file, consumed by composer install/update. This results in a single vendor directory shared across all modules which prevents code duplication and version mismatches.

Composer Manager Overview

Composer Manager addressed our concerns in an easy and well thought out way. And while the module provides excellent documentation, I’ll briefly describe some of the features:

The consolidated composer.json is created at sites/default/files/composer/composer.json by default. Meanwhile, the dependencies are installed to sites/all/vendor by default. Both of these locations are configurable and can easily be changed.

By default, if a module includes a composer.json file and is enabled or disabled via Drush, then Composer Manager automatically

  • Adds or removes the module’s dependencies to or from the consolidated composer.json file.
  • Installs and updates the required dependencies in the vendor directory.

You can also use Drush to manually update the consolidated composer.json file via drush composer-json-rebuild, and manually install or update dependencies via drush composer-manager [COMMAND] [OPTIONS]. For example drush composer-manager update.

Conclusion

We at Savas Labs love any tool or module that makes our development easier, and Composer Manager fits that bill. As Drupal modules start making more and more use of libraries from the greater PHP community, we expect to be using Composer Manager on more and more projects.

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