Merging casts when cloning

src/JoinsHelper.php

@@ -76,6 +76,7 @@ public static function ensureModelIsUniqueToQuery($query): void
             // This can happen if a certain query, *before having interacted with the library
             // `joinRelationship()` method*, was cloned by previous code.
             $query->setModel($model = new ($query->getModel()));
+            $model->mergeCasts($originalModel->getCasts());
 
             // Link the Spl Object ID of the query to the new model...
             static::$modelQueryDictionary[$model] = $querySplObjectId;
@@ -98,6 +99,7 @@ public static function ensureModelIsUniqueToQuery($query): void
 
             // Ensure the model of the cloned query is unique to the query.
             $query->setModel($model = new $originalModel());
+            $model->mergeCasts($originalModel->getCasts());
 
             // Update any `beforeQueryCallbacks` to link to the new `$this` as Eloquent Query,
             // otherwise the reference to the current Eloquent query goes wrong. These query

tests/WithCastsPreservationTest.php

@@ -0,0 +1,36 @@
+<?php
+
+namespace Kirschbaum\PowerJoins\Tests;
+
+use Kirschbaum\PowerJoins\Tests\Models\User;
+
+class WithCastsPreservationTest extends TestCase
+{
+    /** @test */
+    public function test_withcasts_values_preserved_when_joining_relationship()
+    {
+        $query = User::query()
+            ->withCasts(['created_at' => 'date:Y-m']) // Format date as year-month only
+            ->joinRelationship('posts');
+
+        $model = $query->getModel();
+
+        $this->assertArrayHasKey('created_at', $model->getCasts());
+        $this->assertSame('date:Y-m', $model->getCasts()['created_at']);
+    }
+
+    /** @test */
+    public function test_withcasts_values_preserved_after_query_is_cloned()
+    {
+        $query = User::query()
+            ->joinRelationship('posts')
+            ->withCasts(['another_field' => 'date:Y-m']);
+
+        $clonedQuery = $query->clone();
+        $clonedQuery->joinRelationship('images');
+
+        $model = $clonedQuery->getModel();
+        $this->assertArrayHasKey('another_field', $model->getCasts());
+        $this->assertSame('date:Y-m', $model->getCasts()['another_field']);
+    }
+}