From 375bacaf1cd6e581ca77545ef8012f49845e5c40 Mon Sep 17 00:00:00 2001
From: David Smith <dasmith@zero-to-prod.com>
Date: Tue, 2 Jun 2026 20:03:36 -0400
Subject: [PATCH] Add support for single-parameter cast functions in
 class-level casting

Handle cast functions with varying parameter counts by detecting the number of parameters and passing only the required arguments. Add test coverage for readonly properties with class-level cast using native PHP functions like `strtolower`.
---
 src/DataModel.php                             | 17 +++++++++++-----
 .../ClassLevelCastReadonly/ClaimSync.php      | 20 +++++++++++++++++++
 .../ClassLevelCastReadonly/ClaimSyncTest.php  | 18 +++++++++++++++++
 3 files changed, 50 insertions(+), 5 deletions(-)
 create mode 100644 tests/Unit/Describe/ClassLevelCastReadonly/ClaimSync.php
 create mode 100644 tests/Unit/Describe/ClassLevelCastReadonly/ClaimSyncTest.php

diff --git a/src/DataModel.php b/src/DataModel.php
index 930152f..550bce9 100644
--- a/src/DataModel.php
+++ b/src/DataModel.php
@@ -2,13 +2,13 @@
 
 namespace Zerotoprod\DataModel;
 
+use Closure;
 use ReflectionAttribute;
 use ReflectionClass;
 use ReflectionException;
 use ReflectionFunction;
 use ReflectionMethod;
 use ReflectionUnionType;
-use Closure;
 use UnitEnum;
 
 use function is_array;
@@ -87,9 +87,9 @@ trait DataModel
      * @return self
      *
      * @throws PropertyRequiredException         When a required property key is missing.
-     * @throws DuplicateDescribeAttributeException When two methods target the same property.
+     * @throws DuplicateDescribeAttributeException|ReflectionException When two methods target the same property.
      *
-     * @see Describe
+     * @see  Describe
      * @link https://github.com/zero-to-prod/data-model
      */
     public static function from(array|object|null|string $context = [], mixed $instance = null): self
@@ -281,8 +281,15 @@ public static function from(array|object|null|string $context = [], mixed $insta
             }
             /** Class-level cast  */
             if ($ClassDescribe?->cast[$property_type] ?? false) {
-                $self->{$property_name} =
-                    $ClassDescribe?->cast[$property_type]($context[$context_key], $context, $ClassDescribeArguments);
+                $cast = $ClassDescribe->cast[$property_type];
+                $param_count = ($cast instanceof Closure
+                    ? new ReflectionFunction($cast)
+                    : new (is_array($cast) ? ReflectionMethod::class : ReflectionFunction::class)(...(array)$cast))
+                    ->getNumberOfParameters();
+
+                $self->{$property_name} = $param_count === 1
+                    ? $cast($context[$context_key])
+                    : $cast($context[$context_key], $context, $ClassDescribeArguments);
                 continue;
             }
 
diff --git a/tests/Unit/Describe/ClassLevelCastReadonly/ClaimSync.php b/tests/Unit/Describe/ClassLevelCastReadonly/ClaimSync.php
new file mode 100644
index 0000000..1e5c43b
--- /dev/null
+++ b/tests/Unit/Describe/ClassLevelCastReadonly/ClaimSync.php
@@ -0,0 +1,20 @@
+<?php
+
+namespace Tests\Unit\Describe\ClassLevelCastReadonly;
+
+use Zerotoprod\DataModel\DataModel;
+use Zerotoprod\DataModel\Describe;
+
+#[Describe([
+    'cast' => [
+        'string' => 'strtolower'
+    ]
+])]
+class ClaimSync
+{
+    use DataModel;
+
+    public const name = 'name';
+
+    readonly public string $name;
+}
\ No newline at end of file
diff --git a/tests/Unit/Describe/ClassLevelCastReadonly/ClaimSyncTest.php b/tests/Unit/Describe/ClassLevelCastReadonly/ClaimSyncTest.php
new file mode 100644
index 0000000..71ba687
--- /dev/null
+++ b/tests/Unit/Describe/ClassLevelCastReadonly/ClaimSyncTest.php
@@ -0,0 +1,18 @@
+<?php
+
+namespace Tests\Unit\Describe\ClassLevelCastReadonly;
+
+use PHPUnit\Framework\Attributes\Test;
+use Tests\TestCase;
+
+class ClaimSyncTest extends TestCase
+{
+    #[Test] public function class_level_cast_applies_to_readonly_class(): void
+    {
+        $ClaimSync = ClaimSync::from([
+            ClaimSync::name => 'HELLO World',
+        ]);
+
+        $this->assertEquals('hello world', $ClaimSync->name);
+    }
+}
\ No newline at end of file