Add validRegexPattern assertions

README.md

@@ -165,6 +165,7 @@ Method                                              | Description
 `ipv6($value, $message = '')`                       | Check that a string is a valid IPv6
 `email($value, $message = '')`                      | Check that a string is a valid e-mail address
 `notWhitespaceOnly($value, $message = '')`          | Check that a string contains at least one non-whitespace character
+`validRegexPattern($value, $message = '')`          | Check that a string is a valid regular expression pattern
 
 ### File Assertions
 

src/Assert.php

@@ -1227,6 +1227,26 @@ public static function notRegex($value, $pattern, $message = '')
         }
     }
 
+    /**
+     * @psalm-pure
+     *
+     * @param string $value
+     * @param string $message
+     *
+     * @throws InvalidArgumentException
+     */
+    public static function validRegexPattern($value, $message = 'The value %s must be a valid regex pattern.')
+    {
+        static::string($value);
+
+        if (@\preg_match($value, '') === false) {
+            static::reportInvalidArgument(\sprintf(
+                $message,
+                $value
+            ));
+        }
+    }
+
     /**
      * @psalm-pure
      *

src/Mixin.php

@@ -3200,6 +3200,59 @@ public static function allNullOrNotRegex($value, $pattern, $message = '')
         }
     }
 
+    /**
+     * @psalm-pure
+     *
+     * @param string|null $value
+     * @param string      $message
+     *
+     * @return void
+     *
+     * @throws InvalidArgumentException
+     */
+    public static function nullOrValidRegexPattern($value, $message = 'The value %s must be a valid regex pattern.')
+    {
+        null === $value || static::validRegexPattern($value, $message);
+    }
+
+    /**
+     * @psalm-pure
+     *
+     * @param iterable<string> $value
+     * @param string           $message
+     *
+     * @return void
+     *
+     * @throws InvalidArgumentException
+     */
+    public static function allValidRegexPattern($value, $message = 'The value %s must be a valid regex pattern.')
+    {
+        static::isIterable($value);
+
+        foreach ($value as $entry) {
+            static::validRegexPattern($entry, $message);
+        }
+    }
+
+    /**
+     * @psalm-pure
+     *
+     * @param iterable<string|null> $value
+     * @param string                $message
+     *
+     * @return void
+     *
+     * @throws InvalidArgumentException
+     */
+    public static function allNullOrValidRegexPattern($value, $message = 'The value %s must be a valid regex pattern.')
+    {
+        static::isIterable($value);
+
+        foreach ($value as $entry) {
+            null === $entry || static::validRegexPattern($entry, $message);
+        }
+    }
+
     /**
      * @psalm-pure
      *

tests/AssertTest.php

@@ -595,6 +595,11 @@ public function getTests()
             array('uniqueValues', array(array('qwerty', 'qwerty')), false),
             array('uniqueValues', array(array('asdfg', 'qwerty')), true),
             array('uniqueValues', array(array(123, '123')), false),
+            array('validRegexPattern', array('/^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/'), true),
+            array('validRegexPattern', array('/^\(\d{3}\) \d{3}-\d{4}$/'), true),
+            array('validRegexPattern', array('/^https?:\/\/[^\s\/$.?#].[^\s]*$/i'), true),
+            array('validRegexPattern', array('/^(abc/'), false), // Unclosed parenthesis
+            array('validRegexPattern', array('/(?:abc)\1/'), false), // Backreference to non-capturing group
         );
     }