Allow deserialization of nullable arrays

src/Attributes/Field.php

@@ -373,15 +373,19 @@ public function exclude(): bool
      */
     public function validate(mixed $value): bool
     {
+        if ($this->nullable && $value === null) {
+            // If the field is nullable and the value is null, we know it's valid.
+            // No need to call the validate() method further down.
+            return true;
+        }
+
         $valueType = \get_debug_type($value);
 
         if ($this->phpType === $valueType) {
             $valid = true;
         } elseif ($this->phpType === 'mixed') {
             // From a type perspective, mixed accepts anything.
             $valid = true;
-        } elseif ($this->nullable && $valueType === 'null') {
-            $valid = true;
         } elseif (is_object($value) || class_exists($this->phpType) || interface_exists($this->phpType)) {
             // For objects, do a type check and we're done.
             $valid = $value instanceof $this->phpType;

tests/Records/NullablePointList.php

@@ -0,0 +1,19 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Crell\Serde\Records;
+
+use Crell\Serde\Attributes\SequenceField;
+
+readonly final class NullablePointList
+{
+    /**
+     * @param list<Point>|null $points
+     */
+    public function __construct(
+        #[SequenceField(arrayType: Point::class)]
+        public array|null $points = null,
+    ) {
+    }
+}

tests/Records/NullablePointListWithoutConstructor.php

@@ -0,0 +1,24 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Crell\Serde\Records;
+
+use Crell\Serde\Attributes\Field;
+use Crell\Serde\Attributes\SequenceField;
+
+readonly final class NullablePointListWithoutConstructor
+{
+    /**
+     * When the object does not have a constructor, We need to specify the default value.
+     *
+     * In cases of readonly properties, we can't use the default value
+     * as the property can't have a default value in that scenario.
+     *
+     * Therefore, #[Field(default: null)] must be used in such circumstances
+     * to avoid the object instantiation with uninitialized properties.
+     */
+    #[Field(default: null)]
+    #[SequenceField(arrayType: Point::class)]
+    public array|null $points;
+}

tests/SerdeTestCases.php

@@ -68,6 +68,8 @@
 use Crell\Serde\Records\NestedFlattenObject;
 use Crell\Serde\Records\NestedObject;
 use Crell\Serde\Records\NonPromotedDefault;
+use Crell\Serde\Records\NullablePointListWithoutConstructor;
+use Crell\Serde\Records\NullablePointList;
 use Crell\Serde\Records\NullArrays;
 use Crell\Serde\Records\NullProps;
 use Crell\Serde\Records\OptionalPoint;
@@ -120,6 +122,7 @@
 use PHPUnit\Framework\Attributes\Test;
 use PHPUnit\Framework\TestCase;
 use Crell\Serde\Records\UnionTypes;
+use ReflectionClass;
 
 /**
  * Testing base class.
@@ -352,6 +355,16 @@ interfaceProperty: new \DateTimeImmutable('2025-12-25 12:34:56.789'),
                 extendsProperty: new DateTimeExtends('2025-12-25 12:34:56.789'),
             ),
         ];
+        yield 'nullable_list_with_constructor' => [
+            'data' => new NullablePointList(),
+        ];
+
+        $reflected = new ReflectionClass(NullablePointListWithoutConstructor::class);
+        $instance = $reflected->newInstanceWithoutConstructor();
+        $reflected->getProperty('points')->setValue($instance, null);
+        yield 'nullable_list_without_constructor' => [
+            'data' => $instance,
+        ];
     }
 
     public static function value_object_flatten_examples(): \Generator