Create a IsA expression (#396)

* Create a IsA expression

This will allow for testing if a class extends or
implements another code unit, anywhere in the inheritance tree.

---------

Co-authored-by: Herberto Graca <[email protected]>

Author: hgraca

src/Expression/ForClasses/IsA.php

@@ -0,0 +1,44 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Arkitect\Expression\ForClasses;
+
+use Arkitect\Analyzer\ClassDescription;
+use Arkitect\Expression\Description;
+use Arkitect\Expression\Expression;
+use Arkitect\Rules\Violation;
+use Arkitect\Rules\ViolationMessage;
+use Arkitect\Rules\Violations;
+
+final class IsA implements Expression
+{
+    /** @var class-string */
+    private string $allowedFqcn;
+
+    /**
+     * @param class-string $allowedFqcn
+     */
+    public function __construct(string $allowedFqcn)
+    {
+        $this->allowedFqcn = $allowedFqcn;
+    }
+
+    public function describe(ClassDescription $theClass, string $because = ''): Description
+    {
+        return new Description("should inherit from: $this->allowedFqcn", $because);
+    }
+
+    public function evaluate(ClassDescription $theClass, Violations $violations, string $because = ''): void
+    {
+        if (!is_a($theClass->getFQCN(), $this->allowedFqcn, true)) {
+            $violation = Violation::create(
+                $theClass->getFQCN(),
+                ViolationMessage::selfExplanatory($this->describe($theClass, $because)),
+                $theClass->getFilePath()
+            );
+
+            $violations->add($violation);
+        }
+    }
+}

tests/Unit/Expressions/ForClasses/IsATest.php

@@ -0,0 +1,112 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Arkitect\Tests\Unit\Expressions\ForClasses;
+
+use Arkitect\Analyzer\ClassDescriptionBuilder;
+use Arkitect\Expression\ForClasses\IsA;
+use Arkitect\Rules\Violations;
+use Arkitect\Tests\Unit\Expressions\ForClasses\IsOneOfTest\Animal\Dog;
+use Arkitect\Tests\Unit\Expressions\ForClasses\IsOneOfTest\Fruit\Banana;
+use Arkitect\Tests\Unit\Expressions\ForClasses\IsOneOfTest\Fruit\CavendishBanana;
+use Arkitect\Tests\Unit\Expressions\ForClasses\IsOneOfTest\Fruit\DwarfCavendishBanana;
+use Arkitect\Tests\Unit\Expressions\ForClasses\IsOneOfTest\Fruit\FruitInterface;
+use PHPUnit\Framework\TestCase;
+
+final class IsATest extends TestCase
+{
+    public function test_it_should_have_no_violation_when_it_implements(): void
+    {
+        $interface = FruitInterface::class;
+        $isA = new IsA($interface);
+        $classDescription = (new ClassDescriptionBuilder())
+            ->setFilePath('src/Foo.php')
+            ->setClassName(CavendishBanana::class)
+            ->addInterface($interface, 10)
+            ->build();
+
+        $violations = new Violations();
+        $isA->evaluate($classDescription, $violations, '');
+
+        self::assertEquals(0, $violations->count());
+    }
+
+    public function test_it_should_have_no_violation_when_it_extends(): void
+    {
+        $class = Banana::class;
+        $isA = new IsA($class);
+        $classDescription = (new ClassDescriptionBuilder())
+            ->setFilePath('src/Foo.php')
+            ->setClassName(DwarfCavendishBanana::class)
+            ->addExtends($class, 10)
+            ->build();
+
+        $violations = new Violations();
+        $isA->evaluate($classDescription, $violations, '');
+
+        self::assertEquals(0, $violations->count());
+    }
+
+    public function test_it_should_have_violation_if_it_doesnt_extend(): void
+    {
+        $interface = FruitInterface::class;
+        $isA = new IsA($interface);
+        $classDescription = (new ClassDescriptionBuilder())
+            ->setFilePath('src/Foo.php')
+            ->setClassName(Dog::class)
+            ->build();
+
+        $violations = new Violations();
+        $isA->evaluate($classDescription, $violations, '');
+
+        self::assertEquals(1, $violations->count());
+        self::assertEquals(
+            "should inherit from: $interface",
+            $isA->describe($classDescription, '')->toString()
+        );
+    }
+
+    public function test_it_should_have_violation_if_it_doesnt_implement(): void
+    {
+        $class = Banana::class;
+        $isA = new IsA($class);
+        $classDescription = (new ClassDescriptionBuilder())
+            ->setFilePath('src/Foo.php')
+            ->setClassName(Dog::class)
+            ->build();
+
+        $violations = new Violations();
+        $isA->evaluate($classDescription, $violations, '');
+
+        self::assertEquals(1, $violations->count());
+        self::assertEquals(
+            "should inherit from: $class",
+            $isA->describe($classDescription, '')->toString()
+        );
+    }
+}
+
+namespace Arkitect\Tests\Unit\Expressions\ForClasses\IsOneOfTest\Animal;
+
+final class Dog
+{
+}
+
+namespace Arkitect\Tests\Unit\Expressions\ForClasses\IsOneOfTest\Fruit;
+
+interface FruitInterface
+{
+}
+
+class Banana implements FruitInterface
+{
+}
+
+class CavendishBanana extends Banana
+{
+}
+
+final class DwarfCavendishBanana extends CavendishBanana
+{
+}