Install phpstan extension also for root package

composer.json

@@ -8,7 +8,7 @@
     "require": {
         "php": "^7.2 || ^8.0",
         "composer-plugin-api": "^2.0",
-        "phpstan/phpstan": ">=0.11.6"
+        "phpstan/phpstan": ">=0.12.19"
     },
     "require-dev": {
         "composer/composer": "^2.0",

e2e/FooTest.php

@@ -18,4 +18,12 @@ private function requireStd(\stdClass $std): void
 
 	}
 
+	/**
+	 * @return string
+	 */
+	protected function testRootPackageConfigInstall()
+	{
+		return 10;
+	}
+
 }

e2e/composer.json

@@ -13,5 +13,12 @@
 				"symlink": false
 			}
 		}
-	]
+	],
+    "extra": {
+        "phpstan": {
+            "includes": [
+                "phpstan-ext.neon"
+            ]
+        }
+    }
 }

e2e/phpstan-ext.neon

@@ -0,0 +1,6 @@
+parameters:
+    ignoreErrors:
+        -
+            path: FooTest.php
+            message: '~^Method App\\FooTest::testRootPackageConfigInstall\(\) should return string but returns int\.$~'
+            count: 1

src/Plugin.php

@@ -10,6 +10,7 @@
 use Composer\Script\ScriptEvents;
 use Composer\Util\Filesystem;
 use function array_keys;
+use function array_merge;
 use function dirname;
 use function file_exists;
 use function file_put_contents;
@@ -96,9 +97,12 @@ public function process(Event $event): void
 		$notInstalledPackages = [];
 		$installedPackages = [];
 
+		$rootPackage = $composer->getPAckage(); // @phpstan-ignore-line getpackage() for Composer v1, getPackage() for Composer v2
+		$dependencyPackages = $composer->getRepositoryManager()->getLocalRepository()->getPackages();
+
 		$data = [];
 		$fs = new Filesystem();
-		foreach ($composer->getRepositoryManager()->getLocalRepository()->getPackages() as $package) {
+		foreach (array_merge([$rootPackage], $dependencyPackages) as $package) {
 			if (
 				$package->getType() !== 'phpstan-extension'
 				&& !isset($package->getExtra()['phpstan'])
@@ -116,8 +120,13 @@ public function process(Event $event): void
 				}
 				continue;
 			}
-			$absoluteInstallPath = $installationManager->getInstallPath($package);
-			$data[$package->getName()] = [
+
+			$isRootPackage = $package === $rootPackage;
+			$packageName = $isRootPackage ? 'root (' . $package->getName() . ')' : $package->getName();
+			$absoluteInstallPath = $isRootPackage
+				? dirname($composer->getConfig()->getConfigSource()->getName())
+				: $installationManager->getInstallPath($package);
+			$data[$packageName] = [
 				'install_path' => $absoluteInstallPath,
 				'relative_install_path' => $fs->findShortestPath(dirname($generatedConfigFilePath), $absoluteInstallPath, true),
 				'extra' => $package->getExtra()['phpstan'] ?? null,