如何开发一个自定义的 composer 插件（Plugin）？

{
  "name": "your-vendor/my-composer-plugin",
  "type": "composer-plugin",
  "require": {
    "php": "^7.4 || ^8.0",
    "composer-plugin-api": "^2.0",
    "composer/composer": "^2.0"
  },
  "autoload": {
    "psr-4": {
      "MyPlugin\": "src/"
    }
  },
  "extra": {
    "class": "MyPlugin\Plugin"
  }
}

<code><?php

namespace MyPlugin;

use ComposerComposer;
use ComposerEventDispatcherEventSubscriberInterface;
use ComposerIOIOInterface;
use ComposerPluginPluginInterface;
use ComposerScriptScriptEvents;

class Plugin implements PluginInterface, EventSubscriberInterface
{
    protected $composer;
    protected $io;

    public function activate(Composer $composer, IOInterface $io)
    {
        $this->composer = $composer;
        $this->io = $io;
    }

    public static function getSubscribedEvents()
    {
        return [
            ScriptEvents::POST_INSTALL_CMD => 'onPostInstall',
            ScriptEvents::POST_UPDATE_CMD => 'onPostUpdate',
        ];
    }

    public function onPostInstall()
    {
        $this->io->write('<info>自定义插件：安装完成！</info>');
        // 可以在这里执行文件生成、权限检查等操作
    }

    public function onPostUpdate()
    {
        $this->io->write('<info>自定义插件：更新完成！</info>');
    }
}

<?php

namespace MyPlugin;

use ComposerConsoleApplication;
use ComposerIOIOInterface;
use SymfonyComponentConsoleCommandCommand;
use SymfonyComponentConsoleInputInputInterface;
use SymfonyComponentConsoleOutputOutputInterface;

class CustomCommand extends Command
{
    private $io;

    public function __construct(IOInterface $io)
    {
        parent::__construct();
        $this->io = $io;
    }

    protected function configure()
    {
        $this->setName('hello')
             ->setDescription('Say hello from plugin');
    }

    protected function execute(InputInterface $input, OutputInterface $output)
    {
        $this->io->write('Hello from my custom plugin!');
        return 0;
    }
}

public function activate(Composer $composer, IOInterface $io)
{
    $this->composer = $composer;
    $this->io = $io;

    // 注册自定义命令
    if ($composer->getBinDir()) {
        $application = $composer->getAutoloadGenerator()->getInstallationManager();
        $application = $this->composer->getPluginManager()->getApplication();
        if ($application instanceof Application) {
            $application->add(new CustomCommand($io));
        }
    }
}

"repositories": [
  {
    "type": "path",
    "url": "../my-composer-plugin"
  }
],
"require": {
  "your-vendor/my-composer-plugin": "*"
}