286 lines
8.5 KiB
Markdown
286 lines
8.5 KiB
Markdown
<!--
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tagline: Modify and extend Composer's functionality
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-->
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# Setting up and using plugins
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## Synopsis
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You may wish to alter or expand Composer's functionality with your own. For
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example if your environment poses special requirements on the behaviour of
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Composer which do not apply to the majority of its users or if you wish to
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accomplish something with composer in a way that is not desired by most users.
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In these cases you could consider creating a plugin to handle your
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specific logic.
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## Creating a Plugin
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A plugin is a regular Composer package which ships its code as part of the
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package and may also depend on further packages.
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### Plugin Package
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The package file is the same as any other package file but with the following
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requirements:
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1. The [type][1] attribute must be `composer-plugin`.
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2. The [extra][2] attribute must contain an element `class` defining the
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class name of the plugin (including namespace). If a package contains
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multiple plugins, this can be array of class names.
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3. You must require the special package called `composer-plugin-api`
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to define which Plugin API versions your plugin is compatible with.
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The required version of the `composer-plugin-api` follows the same [rules][7]
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as a normal package's.
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The current composer plugin API version is 1.0.0.
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An example of a valid plugin `composer.json` file (with the autoloading
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part omitted):
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```json
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{
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"name": "my/plugin-package",
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"type": "composer-plugin",
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"require": {
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"composer-plugin-api": "^1.0"
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},
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"extra": {
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"class": "My\\Plugin"
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}
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}
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```
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### Plugin Class
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Every plugin has to supply a class which implements the
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[`Composer\Plugin\PluginInterface`][3]. The `activate()` method of the plugin
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is called after the plugin is loaded and receives an instance of
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[`Composer\Composer`][4] as well as an instance of
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[`Composer\IO\IOInterface`][5]. Using these two objects all configuration can
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be read and all internal objects and state can be manipulated as desired.
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Example:
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```php
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<?php
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namespace phpDocumentor\Composer;
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use Composer\Composer;
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use Composer\IO\IOInterface;
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use Composer\Plugin\PluginInterface;
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class TemplateInstallerPlugin implements PluginInterface
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{
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public function activate(Composer $composer, IOInterface $io)
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{
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$installer = new TemplateInstaller($io, $composer);
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$composer->getInstallationManager()->addInstaller($installer);
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}
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}
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```
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## Event Handler
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Furthermore plugins may implement the
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[`Composer\EventDispatcher\EventSubscriberInterface`][6] in order to have its
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event handlers automatically registered with the `EventDispatcher` when the
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plugin is loaded.
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To register a method to an event, implement the method `getSubscribedEvents()`
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and have it return an array. The array key must be the
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[event name](https://getcomposer.org/doc/articles/scripts.md#event-names)
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and the value is the name of the method in this class to be called.
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```php
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public static function getSubscribedEvents()
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{
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return array(
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'post-autoload-dump' => 'methodToBeCalled',
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// ^ event name ^ ^ method name ^
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);
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}
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```
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By default, the priority of an event handler is set to 0. The priority can be
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changed by attaching a tuple where the first value is the method name, as
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before, and the second value is an integer representing the priority.
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Higher integers represent higher priorities. Priority 2 is called before
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priority 1, etc.
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```php
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public static function getSubscribedEvents()
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{
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return array(
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// Will be called before events with priority 0
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'post-autoload-dump' => array('methodToBeCalled', 1)
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);
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}
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```
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If multiple methods should be called, then an array of tuples can be attached
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to each event. The tuples do not need to include the priority. If it is
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omitted, it will default to 0.
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```php
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public static function getSubscribedEvents()
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{
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return array(
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'post-autoload-dump' => array(
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array('methodToBeCalled' ), // Priority defaults to 0
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array('someOtherMethodName', 1), // This fires first
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)
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);
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}
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```
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Here's a complete example:
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```php
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<?php
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namespace Naderman\Composer\AWS;
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use Composer\Composer;
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use Composer\EventDispatcher\EventSubscriberInterface;
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use Composer\IO\IOInterface;
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use Composer\Plugin\PluginInterface;
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use Composer\Plugin\PluginEvents;
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use Composer\Plugin\PreFileDownloadEvent;
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class AwsPlugin implements PluginInterface, EventSubscriberInterface
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{
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protected $composer;
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protected $io;
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public function activate(Composer $composer, IOInterface $io)
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{
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$this->composer = $composer;
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$this->io = $io;
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}
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public static function getSubscribedEvents()
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{
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return array(
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PluginEvents::PRE_FILE_DOWNLOAD => array(
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array('onPreFileDownload', 0)
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),
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);
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}
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public function onPreFileDownload(PreFileDownloadEvent $event)
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{
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$protocol = parse_url($event->getProcessedUrl(), PHP_URL_SCHEME);
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if ($protocol === 's3') {
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$awsClient = new AwsClient($this->io, $this->composer->getConfig());
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$s3RemoteFilesystem = new S3RemoteFilesystem($this->io, $event->getRemoteFilesystem()->getOptions(), $awsClient);
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$event->setRemoteFilesystem($s3RemoteFilesystem);
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}
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}
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}
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```
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## Plugin capabilities
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Composer defines a standard set of capabilities which may be implemented by plugins.
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Their goal is to make the plugin ecosystem more stable as it reduces the need to mess
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with [`Composer\Composer`][4]'s internal state, by providing explicit extension points
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for common plugin requirements.
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Capable Plugins classes must implement the [`Composer\Plugin\Capable`][8] interface
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and declare their capabilities in the `getCapabilities()` method.
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This method must return an array, with the _key_ as a Composer Capability class name,
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and the _value_ as the Plugin's own implementation class name of said Capability:
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```php
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<?php
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namespace My\Composer;
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use Composer\Composer;
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use Composer\IO\IOInterface;
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use Composer\Plugin\PluginInterface;
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use Composer\Plugin\Capable;
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class Plugin implements PluginInterface, Capable
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{
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public function activate(Composer $composer, IOInterface $io)
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{
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}
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public function getCapabilities()
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{
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return array(
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'Composer\Plugin\Capability\CommandProvider' => 'My\Composer\CommandProvider',
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);
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}
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}
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```
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### Command provider
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The [`Composer\Plugin\Capability\CommandProvider`][9] capability allows to register
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additional commands for Composer :
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```php
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<?php
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namespace My\Composer;
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use Composer\Plugin\Capability\CommandProvider as CommandProviderCapability;
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use Symfony\Component\Console\Input\InputInterface;
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use Symfony\Component\Console\Output\OutputInterface;
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use Composer\Command\BaseCommand;
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class CommandProvider implements CommandProviderCapability
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{
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public function getCommands()
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{
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return array(new Command);
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}
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}
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class Command extends BaseCommand
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{
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protected function configure()
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{
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$this->setName('custom-plugin-command');
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}
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protected function execute(InputInterface $input, OutputInterface $output)
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{
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$output->writeln('Executing');
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}
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}
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```
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Now the `custom-plugin-command` is available alongside Composer commands.
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> _Composer commands are based on the [Symfony Console Component][10]._
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## Using Plugins
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Plugin packages are automatically loaded as soon as they are installed and will
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be loaded when composer starts up if they are found in the current project's
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list of installed packages. Additionally all plugin packages installed in the
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`COMPOSER_HOME` directory using the composer global command are loaded before
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local project plugins are loaded.
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> You may pass the `--no-plugins` option to composer commands to disable all
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> installed plugins. This may be particularly helpful if any of the plugins
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> causes errors and you wish to update or uninstall it.
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[1]: ../04-schema.md#type
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[2]: ../04-schema.md#extra
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[3]: https://github.com/composer/composer/blob/master/src/Composer/Plugin/PluginInterface.php
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[4]: https://github.com/composer/composer/blob/master/src/Composer/Composer.php
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[5]: https://github.com/composer/composer/blob/master/src/Composer/IO/IOInterface.php
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[6]: https://github.com/composer/composer/blob/master/src/Composer/EventDispatcher/EventSubscriberInterface.php
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[7]: ../01-basic-usage.md#package-versions
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[8]: https://github.com/composer/composer/blob/master/src/Composer/Plugin/Capable.php
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[9]: https://github.com/composer/composer/blob/master/src/Composer/Plugin/Capability/CommandProvider.php
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[10]: http://symfony.com/doc/current/components/console/introduction.html
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