Note: This project is in development. It currently does not have even any releases. Want to help? Try using it. File issues. Run the tests. Write tests. Thanks. :-)

This plugin is currently being considered for use in the drupalci_testbot. Want to participate in this decision? Talk here: https://www.drupal.org/node/2597778

drupal-merge-plugin is a Composer plugin that allows Drupal extensions to specify their own Composer-based dependencies without extra infrastructure. This includes Drupal modules, themes, and profiles.

This plugin is an evolution of the plugin_manager module concept, using Drupal extension discovery to merge Composer-based dependencies.

It builds on the Wikimedia project's composer-merge-plugin, and inherits some of that project's behaviors.

You can read the documentation for Wikimedia's composer-merge-plugin here: https://github.com/wikimedia/composer-merge-plugin

Adding packagist.drupal-composer.org to your composer.json file is enough to help it find Drupal extensions, and install them along with their dependencies.

However, if you need to update, or re-install without a lock file, that won't be enough to manage those dependencies.

With this plugin, that's possible.

Once you're using this plugin, it will search for composer.json files within the extensions present in your Drupal project's file system, and then try to satisfy them. If they can't be satisfied (due to version constraints, etc.) then Composer will tell you.

Note that the plugin does not care if a given extension is enabled or not. It will satisfy all extensions in the Drupal filesystem regardless of the extension's enabled status.

At the command line, type this:

$ composer require mile23/drupal-merge-plugin

This adds the plugin to your Drupal project.

In order to get Drupal extensions using Composer, you must then add the special Drupal Packagist clone to your repositories section. There are instructions here: https://www.drupal.org/node/2718229

Basically, add a repository like this to your composer.json file:

"repositories": {
    "drupal": {
        "type": "composer",
        "url":  "https://packages.drupal.org/8"
    }
}

Then you can add Drupal extensions:

$ composer require drupal/your-module-here

You can add command-line scripts to your composer.json like this:

"scripts": {
    "list-extensions": "Mile23\\DrupalMerge\\Script::listExtensions",
    "list-managed-extensions": "Mile23\\DrupalMerge\\Script::listManagedExtensions",
    "list-unmanaged-extensions": "Mile23\\DrupalMerge\\Script::listUnmanagedExtensions",
},

Once you've done that, you can list available modules by their Composer status.

• composer list-extensions gives you all discoverable Drupal extensions which have a composer.json file.
• composer list-managed-extensions gives you the Drupal extensions which are in the requires section of the current Composer package. Restated: If the extension is in your composer.json file, it appears in this list.
• composer list-unmanaged-extensions gives you a list of extensions which have composer.json files, but which are not listed as dependencies in the current project. These would be extensions downloaded as tarballs, for instance.

Drupal extensions SHOULD NOT specify that they depend on this plugin. Only project-level composer.json files should use this plugin.

This plugin's behavior might also conflict with other Composer solutions built by the Drupal community.

You can supply a composer.json file per extension, at any folder depth supported by normal Drupal module discovery.

Your composer.json file must be in the same directory as the extension's .info.yml file.

Your comopser.json file should pass the test of running composer validate from the command line.

If your composer.json file does not specify requires and/or requires-dev, then this plugin probably won't be terribly useful to you.

drupal-merge-plugin will use the same merging rules as wikimedia/composer-merge-plugin. That is, requires and requires-dev will be merged, along with other sections of composer.json. Consult the composer-merge-plugin documentation for more information.

You should NOT use the autoload feature of Composer for your extension. Drupal will autoload the module as needed.

drupal-merge-plugin uses the same project type naming convention as composer-installers. This means your module's type field should be drupal-module. This allows the composer-installer plugin to place your module in the proper directory, and allows drupal-merge-plugin to discover it.