Allow use callable rules into Nested

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## 2.3.1 under development
 
+- Enh #770: Allow use callable rules into `Nested` (@Enjoyzz)
 - Bug #751: Fix incorrect `Nested` rule processing within `Each` (@Enjoyzz)
 
 ## 2.3.0 May 07, 2025

src/Rule/Nested.php

@@ -201,7 +201,7 @@
      * validated value is empty / not passed. See {@see SkipOnEmptyInterface}.
      * @param bool $skipOnError Whether to skip this `Nested` rule with all defined {@see $rules} if any of the previous
      * rules gave an error. See {@see SkipOnErrorInterface}.
-     * @param Closure|null $when  A callable to define a condition for applying this `Nested` rule with all defined
+     * @param Closure|null $when A callable to define a condition for applying this `Nested` rule with all defined
      * {@see $rules}. See {@see WhenInterface}.
      *
      * @psalm-param SkipOnEmptyValue $skipOnEmpty
@@ -453,13 +453,14 @@
             $rules = iterator_to_array($rules);
         }
 
-        /** @var mixed $rule */
         foreach ($rules as &$rule) {
-            if (is_iterable($rule)) {
+            if (is_callable($rule)) {
+                $rule = new Callback($rule);
+            } elseif (is_iterable($rule)) {
                 self::ensureArrayHasRules($rule);
             } elseif (!$rule instanceof RuleInterface) {
                 $message = sprintf(
-                    'Every rule must be an instance of %s, %s given.',
+                    'Every rule must be an instance of %s or a callable, %s given.',
                     RuleInterface::class,
                     get_debug_type($rule)
                 );

tests/Rule/NestedTest.php

@@ -226,7 +226,7 @@ public function testGetOptionsWithNotRule(): void
         $this->expectException(InvalidArgumentException::class);
 
         $ruleInterfaceName = RuleInterface::class;
-        $message = "Every rule must be an instance of $ruleInterfaceName, class@anonymous given.";
+        $message = "Every rule must be an instance of $ruleInterfaceName or a callable, class@anonymous given.";
         $this->expectExceptionMessage($message);
 
         $rule = new Nested([
@@ -1440,7 +1440,7 @@ public function testValidationFailedWithDetailedErrors(mixed $data, array $rules
     public function testInitWithNotARule(): void
     {
         $this->expectException(InvalidArgumentException::class);
-        $message = 'Every rule must be an instance of Yiisoft\Validator\RuleInterface, string given.';
+        $message = 'Every rule must be an instance of Yiisoft\Validator\RuleInterface or a callable, string given.';
         $this->expectExceptionMessage($message);
         new Nested([
             'data' => new Nested([
@@ -1502,6 +1502,17 @@ protected function getDifferentRuleInHandlerItems(): array
         return [Nested::class, NestedHandler::class];
     }
 
+    public function testUseCallableRules()
+    {
+        $rules = new Nested([
+            'tag' => static fn() => (new Result())->addError('Too short.'),
+        ]);
+        $data = ['tag' => 'value'];
+
+        $result = (new Validator())->validate($data, $rules);
+        $this->assertSame(['tag' => ['Too short.']], $result->getErrorMessagesIndexedByPath());
+    }
+
     public function testWithArrayOfObjects(): void
     {
         $obj = (new NestedIterableOfObjects())->setCollection([