Fix string rule array merge

Author: CWAscend

src/Resolvers/DataValidationRulesResolver.php

@@ -244,6 +244,10 @@ protected function resolveRules(
         $rulesFromRulesMethod = app()->call([$class->name, 'rules'], ['context' => $validationContext]);
 
         if ($this->shouldMergeRules($class)) {
+            $rulesFromRulesMethod = collect($rulesFromRulesMethod)->map(
+                fn (string|array $rules) => is_array($rules) ? $rules : explode('|', $rules)
+            )->all();
+
             $dataRules->rules = array_merge_recursive($dataRules->rules, $rulesFromRulesMethod);
             return;
         }

tests/Attributes/Validation/MergeRulesetTest.php

@@ -1,7 +1,9 @@
 <?php
 
 use Illuminate\Validation\ValidationException;
+use Spatie\LaravelData\Data;
 use Spatie\LaravelData\Tests\Fakes\DataWithMergedRuleset;
+use Spatie\LaravelData\Tests\Fakes\DataWithMergedStringRuleset;
 
 it('it will merge validation rules', function () {
     try {
@@ -21,3 +23,28 @@
     }
 });
 
+it('it will merge validation rules using string rules', function () {
+    try {
+        Data::validate(['first_name' => str_repeat('a', 1)]);
+    } catch (ValidationException $exception) {
+        expect($exception->errors())->toMatchArray([
+            'first_name' => ['The first name field must be at least 2 characters.']
+        ]);
+    }
+
+    try {
+        DataWithMergedStringRuleset::validate(['first_name' => str_repeat('a', 11)]);
+    } catch (ValidationException $exception) {
+        expect($exception->errors())->toMatchArray([
+            'first_name' => ['The first name field must not be greater than 10 characters.']
+        ]);
+    }
+
+    try {
+        DataWithMergedStringRuleset::validate(['first_name' => 'a123']);
+    } catch (ValidationException $exception) {
+        expect($exception->errors())->toMatchArray([
+            'first_name' => ['The first name field must only contain letters.']
+        ]);
+    }
+});

tests/Fakes/DataWithMergedStringRuleset.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace Spatie\LaravelData\Tests\Fakes;
+
+use Spatie\LaravelData\Attributes\MergeRules;
+use Spatie\LaravelData\Attributes\Validation\Max;
+use Spatie\LaravelData\Data;
+
+#[MergeRules]
+class DataWithMergedStringRuleset extends Data
+{
+    public function __construct(
+        #[Max(10)]
+        public string $first_name,
+    ) {
+    }
+
+    public static function rules(): array
+    {
+        return [
+            'first_name' => 'min:2|alpha'
+        ];
+    }
+}