Enable constructing DTOs *without* passing parameter array.

src/DataTransferObject.php

@@ -20,12 +20,12 @@ abstract class DataTransferObject
      *
      * @return \Spatie\DataTransferObject\ImmutableDataTransferObject|static
      */
-    public static function immutable(array $parameters): ImmutableDataTransferObject
+    public static function immutable(array $parameters = []): ImmutableDataTransferObject
     {
         return new ImmutableDataTransferObject(new static($parameters));
     }
 
-    public function __construct(array $parameters)
+    public function __construct(array $parameters = [])
     {
         $class = new ReflectionClass(static::class);
 

tests/DataTransferTransferObjectTest.php → tests/DataTransferObjectTest.php

@@ -369,4 +369,18 @@ public function empty_dto_objects_can_be_cast_using_arrays()
 
         $this->assertInstanceOf(EmptyChild::class, $object->child);
     }
+
+    /** @test */
+    public function empty_constructor_is_supported()
+    {
+        $valueObject = new class() extends DataTransferObject {
+            /** @var string */
+            public $foo = 'abc';
+
+            /** @var bool|null */
+            public $bar;
+        };
+
+        $this->assertEquals(['foo' => 'abc', 'bar' => null], $valueObject->all());
+    }
 }

tests/ImmutableTest.php

@@ -4,6 +4,7 @@
 
 use Spatie\DataTransferObject\DataTransferObjectError;
 use Spatie\DataTransferObject\Tests\TestClasses\TestDataTransferObject;
+use Spatie\DataTransferObject\Tests\TestClasses\NullableTestDataTransferObject;
 
 class ImmutableTest extends TestCase
 {
@@ -30,4 +31,12 @@ public function method_calls_are_proxied()
 
         $this->assertEquals(['testProperty' => 1], $dto->toArray());
     }
+
+    /** @test */
+    public function passing_parameters_is_not_required()
+    {
+        $dto = NullableTestDataTransferObject::immutable();
+
+        $this->assertEquals(['foo' => 'abc', 'bar' => null], $dto->toArray());
+    }
 }

tests/TestClasses/NullableTestDataTransferObject.php

@@ -0,0 +1,16 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Spatie\DataTransferObject\Tests\TestClasses;
+
+use Spatie\DataTransferObject\DataTransferObject;
+
+class NullableTestDataTransferObject extends DataTransferObject
+{
+    /** @var string */
+    public $foo = 'abc';
+
+    /** @var bool|null */
+    public $bar;
+}