Added optional directive

src/OptionalDirective.php

@@ -0,0 +1,61 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace Graphpinator\ExtraTypes;
+
+final class OptionalDirective extends \Graphpinator\Typesystem\Directive implements
+    \Graphpinator\Typesystem\Location\ArgumentDefinitionLocation
+{
+    protected const NAME = 'optional';
+    protected const DESCRIPTION = 'Input value for this argument can be either omitted or have non-null value.';
+
+    public static function isPure() : bool
+    {
+        return true;
+    }
+
+    public function validateArgumentUsage(
+        \Graphpinator\Typesystem\Argument\Argument $argument,
+        \Graphpinator\Value\ArgumentValueSet $arguments,
+    ) : bool
+    {
+        return true;
+    }
+
+    public function validateVariance(
+        ?\Graphpinator\Value\ArgumentValueSet $biggerSet,
+        ?\Graphpinator\Value\ArgumentValueSet $smallerSet,
+    ) : void
+    {
+        if ($biggerSet instanceof \Graphpinator\Value\ArgumentValueSet &&
+            $smallerSet instanceof \Graphpinator\Value\ArgumentValueSet &&
+            $biggerSet->isSame($smallerSet)) {
+            return;
+        }
+
+        throw new \Exception();
+    }
+
+    public function resolveArgumentDefinition(
+        \Graphpinator\Value\ArgumentValueSet $arguments,
+        \Graphpinator\Value\ArgumentValue $argumentValue,
+    ) : void
+    {
+        if ($argumentValue->getValue() instanceof \Graphpinator\Value\NullInputedValue) {
+            throw new class extends \Graphpinator\Exception\GraphpinatorBase {
+                public const MESSAGE = 'Input field is @optional and therefore cannot contain null value.';
+
+                public function isOutputable(): bool
+                {
+                    return true;
+                }
+            };
+        }
+    }
+
+    protected function getFieldDefinition() : \Graphpinator\Typesystem\Argument\ArgumentSet
+    {
+        return new \Graphpinator\Typesystem\Argument\ArgumentSet();
+    }
+}

tests/Unit/OptionalDirectiveTest.php

@@ -0,0 +1,56 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace Graphpinator\ExtraTypes\Tests\Unit;
+
+final class OptionalDirectiveTest extends \PHPUnit\Framework\TestCase
+{
+    public function testValue() : void
+    {
+        $value = self::getInput()->accept(
+            new \Graphpinator\Value\ConvertRawValueVisitor((object) ['arg1' => 'Value'], new \Graphpinator\Common\Path()),
+        );
+        $value->applyVariables(new \Graphpinator\Normalizer\VariableValueSet([]));
+
+        self::assertInstanceOf(\Graphpinator\Value\InputValue::class, $value);
+    }
+
+    public function testOmitted() : void
+    {
+        $value = self::getInput()->accept(
+            new \Graphpinator\Value\ConvertRawValueVisitor((object) [], new \Graphpinator\Common\Path()),
+        );
+        $value->applyVariables(new \Graphpinator\Normalizer\VariableValueSet([]));
+
+        self::assertInstanceOf(\Graphpinator\Value\InputValue::class, $value);
+    }
+
+    public function testInvalid() : void
+    {
+        $this->expectException(\Graphpinator\Exception\GraphpinatorBase::class);
+        $this->expectExceptionMessage('Input field is @optional and therefore cannot contain null value.');
+
+        $value = self::getInput()->accept(
+            new \Graphpinator\Value\ConvertRawValueVisitor((object) ['arg1' => null], new \Graphpinator\Common\Path()),
+        );
+        $value->applyVariables(new \Graphpinator\Normalizer\VariableValueSet([]));
+    }
+
+    private static function getInput() : \Graphpinator\Typesystem\InputType
+    {
+        return new class extends \Graphpinator\Typesystem\InputType {
+            protected const NAME = 'ConstraintInput';
+
+            protected function getFieldDefinition() : \Graphpinator\Typesystem\Argument\ArgumentSet
+            {
+                return new \Graphpinator\Typesystem\Argument\ArgumentSet([
+                    \Graphpinator\Typesystem\Argument\Argument::create(
+                        'arg1',
+                        \Graphpinator\Typesystem\Container::String(),
+                    )->addDirective(new \Graphpinator\ExtraTypes\OptionalDirective()),
+                ]);
+            }
+        };
+    }
+}