Initial commit

codefu/Installer.php

+<?php
+
+namespace Foobar;
+
+use Composer\Installers;
+use Composer\Package\PackageInterface;
+use Composer\Repository\InstalledRepositoryInterface;
+
+class Installer extends \Composer\Installers\Installer {
+  public function uninstall(InstalledRepositoryInterface $repo, PackageInterface $package) {
+    echo "A1\n";
+    if ('web/core' != substr($this->getInstallPath($package), -8)) {
+      return parent::uninstall($repo, $package);
+    }
+    echo "B1\n";
+    return NULL;
+  }
+
+  public function cleanup($type, PackageInterface $package, ?PackageInterface $prevPackage = null) {
+    echo "A2\n";
+    if ('web/core' != substr($this->getInstallPath($package), -8)) {
+      return parent::cleanup($type, $package, $prevPackage);
+    }
+    echo "B2\n";
+    return NULL;
+  }
+  
+}

codefu/Plugin.php

+<?php
+
+namespace Foobar;
+
+use Composer\Composer;
+use Composer\IO\IOInterface;
+use Composer\Plugin\PluginInterface;
+
+class Plugin implements PluginInterface {
+  public function activate(Composer $composer, IOInterface $io) {
+    $installer = new Installer($io, $composer);
+    $composer->getInstallationManager()->addInstaller($installer);
+    echo "\n\nACTIVATE!!\n\n";
+  }
+
+  public function deactivate(Composer $composer, IOInterface $io) {
+    echo "\n\nDEACTIVATE!!\n\n";
+  }
+
+  public function uninstall(Composer $composer, IOInterface $io) {
+    echo "\n\nUNINSTALL!!\n\n";
+  }
+}

composer.json

+{
+  "name": "foobar/plugin",
+  "type": "composer-plugin",
+  "require": {
+    "composer-plugin-api": "^2.0"
+  },
+  "require-dev": {
+    "composer/composer": "^2.0"
+  },
+  "extra": {
+    "class": "Foobar\\Plugin2"
+  },
+  "autoload": {
+    "psr-4": {
+      "Foobar\\": "codefu/"
+    }
+  }
+}