Added rule for enforcing final class usage

extension.neon

@@ -7,3 +7,4 @@ parameters:
 		- stubs/Money/MoneyParser.stub
 rules:
     - Ibexa\PHPStan\Rules\NoConfigResolverParametersInConstructorRule
+    - Ibexa\PHPStan\Rules\FinalClassRule

rules/FinalClassRule.php

@@ -0,0 +1,77 @@
+<?php
+
+/**
+ * @copyright Copyright (C) Ibexa AS. All rights reserved.
+ * @license For full copyright and license information view LICENSE file distributed with this source code.
+ */
+declare(strict_types=1);
+
+namespace Ibexa\PHPStan\Rules;
+
+use PhpParser\Node;
+use PHPStan\Analyser\Scope;
+use PHPStan\Reflection\ReflectionProvider;
+use PHPStan\Rules\Rule;
+use PHPStan\Rules\RuleErrorBuilder;
+
+/**
+ * @implements \PHPStan\Rules\Rule<\PhpParser\Node\Stmt\Class_>
+ */
+final class FinalClassRule implements Rule
+{
+    private ReflectionProvider $reflectionProvider;
+
+    public function __construct(
+        ReflectionProvider $reflectionProvider
+    ) {
+        $this->reflectionProvider = $reflectionProvider;
+    }
+
+    public function getNodeType(): string
+    {
+        return Node\Stmt\Class_::class;
+    }
+
+    public function processNode(Node $node, Scope $scope): array
+    {
+        // Skip anonymous classes
+        if (!isset($node->namespacedName)) {
+            return [];
+        }
+
+        $className = $node->namespacedName->toString();
+
+        if (!$this->reflectionProvider->hasClass($className)) {
+            return [];
+        }
+
+        $reflection = $this->reflectionProvider->getClass($className);
+
+        // Skip if already final
+        if ($reflection->isFinal()) {
+            return [];
+        }
+
+        // Skip if abstract (abstract classes shouldn't be final)
+        if ($reflection->isAbstract()) {
+            return [];
+        }
+
+        // Skip interfaces and traits
+        if ($reflection->isInterface() || $reflection->isTrait()) {
+            return [];
+        }
+
+        return [
+            RuleErrorBuilder::message(
+                sprintf(
+                    'Class %s is not final. All non-abstract classes should be final.',
+                    $reflection->getName()
+                )
+            )
+                ->identifier('class.notFinal')
+                ->tip('Add "final" keyword to the class declaration.')
+                ->build(),
+        ];
+    }
+}

tests/rules/FinalClassRuleTest.php

@@ -0,0 +1,53 @@
+<?php
+
+/**
+ * @copyright Copyright (C) Ibexa AS. All rights reserved.
+ * @license For full copyright and license information view LICENSE file distributed with this source code.
+ */
+declare(strict_types=1);
+
+namespace Ibexa\Tests\PHPStan\Rules;
+
+use Ibexa\PHPStan\Rules\FinalClassRule;
+use PHPStan\Rules\Rule;
+use PHPStan\Testing\RuleTestCase;
+
+/**
+ * @extends \PHPStan\Testing\RuleTestCase<\Ibexa\PHPStan\Rules\FinalClassRule>
+ */
+final class FinalClassRuleTest extends RuleTestCase
+{
+    protected function getRule(): Rule
+    {
+        return new FinalClassRule($this->createReflectionProvider());
+    }
+
+    public function testRule(): void
+    {
+        $this->analyse(
+            [
+                __DIR__ . '/Fixtures/FinalClass/NonFinalClass.php',
+            ],
+            [
+                [
+                    'Class Ibexa\Tests\PHPStan\Rules\Fixtures\FinalClass\NonFinalClass is not final. All non-abstract classes should be final.',
+                    11,
+                    'Add "final" keyword to the class declaration.',
+                ],
+            ]
+        );
+    }
+
+    public function testNoErrorsOnFinalAndAbstractClassesAndInterfaces(): void
+    {
+        $this->analyse(
+            [
+                __DIR__ . '/Fixtures/FinalClass/FinalClass.php',
+                __DIR__ . '/Fixtures/FinalClass/AbstractClass.php',
+                __DIR__ . '/Fixtures/FinalClass/SomeInterface.php',
+                __DIR__ . '/Fixtures/FinalClass/SomeTrait.php',
+            ],
+            []
+        );
+    }
+}

tests/rules/Fixtures/FinalClass/AbstractClass.php

@@ -0,0 +1,13 @@
+<?php
+
+/**
+ * @copyright Copyright (C) Ibexa AS. All rights reserved.
+ * @license For full copyright and license information view LICENSE file distributed with this source code.
+ */
+declare(strict_types=1);
+
+namespace Ibexa\Tests\PHPStan\Rules\Fixtures\FinalClass;
+
+abstract class AbstractClass
+{
+}

tests/rules/Fixtures/FinalClass/FinalClass.php

@@ -0,0 +1,13 @@
+<?php
+
+/**
+ * @copyright Copyright (C) Ibexa AS. All rights reserved.
+ * @license For full copyright and license information view LICENSE file distributed with this source code.
+ */
+declare(strict_types=1);
+
+namespace Ibexa\Tests\PHPStan\Rules\Fixtures\FinalClass;
+
+final class FinalClass
+{
+}

tests/rules/Fixtures/FinalClass/NonFinalClass.php

@@ -0,0 +1,13 @@
+<?php
+
+/**
+ * @copyright Copyright (C) Ibexa AS. All rights reserved.
+ * @license For full copyright and license information view LICENSE file distributed with this source code.
+ */
+declare(strict_types=1);
+
+namespace Ibexa\Tests\PHPStan\Rules\Fixtures\FinalClass;
+
+class NonFinalClass
+{
+}

tests/rules/Fixtures/FinalClass/SomeInterface.php

@@ -0,0 +1,13 @@
+<?php
+
+/**
+ * @copyright Copyright (C) Ibexa AS. All rights reserved.
+ * @license For full copyright and license information view LICENSE file distributed with this source code.
+ */
+declare(strict_types=1);
+
+namespace Ibexa\Tests\PHPStan\Rules\Fixtures\FinalClass;
+
+interface SomeInterface
+{
+}

tests/rules/Fixtures/FinalClass/SomeTrait.php

@@ -0,0 +1,16 @@
+<?php
+
+/**
+ * @copyright Copyright (C) Ibexa AS. All rights reserved.
+ * @license For full copyright and license information view LICENSE file distributed with this source code.
+ */
+declare(strict_types=1);
+
+namespace Ibexa\Tests\PHPStan\Rules\Fixtures\FinalClass;
+
+/**
+ * @phpstan-ignore trait.unused
+ */
+trait SomeTrait
+{
+}