Add ForbiddenInheritanceRule

README.md

@@ -221,6 +221,76 @@ final class Alert
 
 <br>
 
+### ForbiddenInheritanceRule
+
+Forbids the use of class inheritance in Twig Components. Composition via traits should be used instead.
+This promotes better code reusability and avoids tight coupling between components.
+
+> [!TIP]
+> Another alternative is to use [Class Variant Authority](https://symfony.com/bundles/ux-twig-component/current/index.html#component-with-complex-variants-cva) to create variations of a base component without inheritance or traits,
+> for example `<twig:Alert variant="success"></twig:Alert>` instead of `<twig:AlertSuccess></twig:AlertSuccess>`.
+
+```yaml
+rules:
+    - Kocal\PHPStanSymfonyUX\Rules\TwigComponent\ForbiddenInheritanceRule
+```
+
+```php
+// src/Twig/Components/Alert.php
+namespace App\Twig\Components;
+
+use Symfony\UX\TwigComponent\Attribute\AsTwigComponent;
+
+abstract class BaseComponent
+{
+    public string $name;
+}
+
+#[AsTwigComponent]
+final class Alert extends BaseComponent
+{
+}
+```
+
+:x:
+
+<br>
+
+```php
+// src/Twig/Components/Alert.php
+namespace App\Twig\Components;
+
+use Symfony\UX\TwigComponent\Attribute\AsTwigComponent;
+
+trait CommonComponentTrait
+{
+    public string $name;
+}
+
+#[AsTwigComponent]
+final class Alert
+{
+    use CommonComponentTrait;
+}
+```
+
+```php
+// src/Twig/Components/Alert.php
+namespace App\Twig\Components;
+
+use Symfony\UX\TwigComponent\Attribute\AsTwigComponent;
+
+#[AsTwigComponent]
+final class Alert
+{
+    public string $name;
+}
+```
+
+:+1:
+
+<br>
+
 ### PublicPropertiesShouldBeCamelCaseRule
 
 Enforces that all public properties in Twig Components follow camelCase naming convention.

src/Rules/TwigComponent/ForbiddenInheritanceRule.php

@@ -0,0 +1,43 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Kocal\PHPStanSymfonyUX\Rules\TwigComponent;
+
+use Kocal\PHPStanSymfonyUX\NodeAnalyzer\AttributeFinder;
+use PhpParser\Node;
+use PhpParser\Node\Stmt\Class_;
+use PHPStan\Analyser\Scope;
+use PHPStan\Rules\Rule;
+use PHPStan\Rules\RuleErrorBuilder;
+use Symfony\UX\TwigComponent\Attribute\AsTwigComponent;
+
+/**
+ * @implements Rule<Class_>
+ */
+final class ForbiddenInheritanceRule implements Rule
+{
+    public function getNodeType(): string
+    {
+        return Class_::class;
+    }
+
+    public function processNode(Node $node, Scope $scope): array
+    {
+        if (! AttributeFinder::findAttribute($node, AsTwigComponent::class)) {
+            return [];
+        }
+
+        if ($node->extends !== null) {
+            return [
+                RuleErrorBuilder::message('Using class inheritance in a Twig component is forbidden, use traits for composition instead.')
+                    ->identifier('symfonyUX.twigComponent.forbiddenClassInheritance')
+                    ->line($node->extends->getLine())
+                    ->tip('Consider using traits to share common functionality between Twig components.')
+                    ->build(),
+            ];
+        }
+
+        return [];
+    }
+}

tests/Rules/TwigComponent/ForbiddenInheritanceRule/Fixture/ComponentUsingTrait.php

@@ -0,0 +1,18 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Kocal\PHPStanSymfonyUX\Tests\Rules\TwigComponent\ForbiddenInheritanceRule\Fixture;
+
+use Symfony\UX\TwigComponent\Attribute\AsTwigComponent;
+
+trait CommonComponentTrait
+{
+    public string $name;
+}
+
+#[AsTwigComponent]
+final class ComponentUsingTrait
+{
+    use CommonComponentTrait;
+}

tests/Rules/TwigComponent/ForbiddenInheritanceRule/Fixture/ComponentWithInheritance.php

@@ -0,0 +1,17 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Kocal\PHPStanSymfonyUX\Tests\Rules\TwigComponent\ForbiddenInheritanceRule\Fixture;
+
+use Symfony\UX\TwigComponent\Attribute\AsTwigComponent;
+
+abstract class BaseComponent
+{
+    public string $name;
+}
+
+#[AsTwigComponent]
+final class ComponentWithInheritance extends BaseComponent
+{
+}

tests/Rules/TwigComponent/ForbiddenInheritanceRule/Fixture/ComponentWithoutInheritance.php

@@ -0,0 +1,13 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Kocal\PHPStanSymfonyUX\Tests\Rules\TwigComponent\ForbiddenInheritanceRule\Fixture;
+
+use Symfony\UX\TwigComponent\Attribute\AsTwigComponent;
+
+#[AsTwigComponent]
+final class ComponentWithoutInheritance
+{
+    public string $name;
+}

tests/Rules/TwigComponent/ForbiddenInheritanceRule/Fixture/NotAComponent.php

@@ -0,0 +1,14 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Kocal\PHPStanSymfonyUX\Tests\Rules\TwigComponent\ForbiddenInheritanceRule\Fixture;
+
+abstract class BaseClass
+{
+    public string $name;
+}
+
+final class NotAComponent extends BaseClass
+{
+}

tests/Rules/TwigComponent/ForbiddenInheritanceRule/ForbiddenInheritanceRuleTest.php

@@ -0,0 +1,57 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Kocal\PHPStanSymfonyUX\Tests\Rules\TwigComponent\ForbiddenInheritanceRule;
+
+use Kocal\PHPStanSymfonyUX\Rules\TwigComponent\ForbiddenInheritanceRule;
+use PHPStan\Rules\Rule;
+use PHPStan\Testing\RuleTestCase;
+
+/**
+ * @extends RuleTestCase<ForbiddenInheritanceRule>
+ */
+final class ForbiddenInheritanceRuleTest extends RuleTestCase
+{
+    public function testViolations(): void
+    {
+        $this->analyse(
+            [__DIR__ . '/Fixture/ComponentWithInheritance.php'],
+            [
+                [
+                    'Using class inheritance in a Twig component is forbidden, use traits for composition instead.',
+                    15,
+                    'Consider using traits to share common functionality between Twig components.',
+                ],
+            ]
+        );
+    }
+
+    public function testNoViolations(): void
+    {
+        $this->analyse(
+            [__DIR__ . '/Fixture/NotAComponent.php'],
+            []
+        );
+
+        $this->analyse(
+            [__DIR__ . '/Fixture/ComponentWithoutInheritance.php'],
+            []
+        );
+
+        $this->analyse(
+            [__DIR__ . '/Fixture/ComponentUsingTrait.php'],
+            []
+        );
+    }
+
+    public static function getAdditionalConfigFiles(): array
+    {
+        return [__DIR__ . '/config/configured_rule.neon'];
+    }
+
+    protected function getRule(): Rule
+    {
+        return self::getContainer()->getByType(ForbiddenInheritanceRule::class);
+    }
+}

tests/Rules/TwigComponent/ForbiddenInheritanceRule/config/configured_rule.neon

@@ -0,0 +1,2 @@
+rules:
+    - Kocal\PHPStanSymfonyUX\Rules\TwigComponent\ForbiddenInheritanceRule