feat(metadata): expose a default attribute on parameters

Author: aegypius

src/Metadata/Parameter.php

@@ -56,6 +56,7 @@ public function __construct(
         protected ?bool $castToArray = null,
         protected ?bool $castToNativeType = null,
         protected mixed $castFn = null,
+        protected mixed $default = null,
     ) {
     }
 
@@ -139,7 +140,7 @@ public function getSecurityMessage(): ?string
      */
     public function getValue(mixed $default = new ParameterNotFound()): mixed
     {
-        return $this->extraProperties['_api_values'] ?? $default;
+        return $this->extraProperties['_api_values'] ?? $this->default ?? $default;
     }
 
     /**
@@ -370,4 +371,12 @@ public function withCastFn(mixed $castFn): self
 
         return $self;
     }
+
+    public function withDefault(mixed $default): self
+    {
+        $self = clone $this;
+        $self->default = $default;
+
+        return $self;
+    }
 }

src/Metadata/Tests/ParameterTest.php

@@ -13,16 +13,41 @@
 
 namespace ApiPlatform\Metadata\Tests;
 
+use ApiPlatform\Metadata\Parameter;
 use ApiPlatform\Metadata\QueryParameter;
 use ApiPlatform\State\ParameterNotFound;
+use PHPUnit\Framework\Attributes\DataProvider;
 use PHPUnit\Framework\TestCase;
 
 class ParameterTest extends TestCase
 {
     public function testDefaultValue(): void
     {
-        $parameter = new QueryParameter();
-        $this->assertSame('test', $parameter->getValue('test'));
-        $this->assertInstanceOf(ParameterNotFound::class, $parameter->getValue());
+        $this->assertInstanceOf(ParameterNotFound::class, (new QueryParameter())->getValue());
+    }
+
+    #[DataProvider('provideDefaultValueCases')]
+    public function testDefaultValueWithFallbackValue(Parameter $parameter, mixed $fallbackValue, mixed $expectedDefault): void
+    {
+        $this->assertSame($expectedDefault, $parameter->getValue($fallbackValue));
+    }
+
+
+    /** @return iterable<[Parameter, mixed, mixed]> */
+    public static function provideDefaultValueCases(): iterable
+    {
+        $fallbackValue = new ParameterNotFound();
+
+        yield 'no default specified' => [
+            new QueryParameter(), $fallbackValue, $fallbackValue,
+        ];
+
+        yield 'with a default specified' => [
+            new QueryParameter(default: false), $fallbackValue, false,
+        ];
+
+        yield 'with null as default' => [
+            new QueryParameter(default: null), $fallbackValue,  $fallbackValue,
+        ];
     }
 }