[5.1] Form: Add regex validation rule

libraries/src/Form/Rule/RegexRule.php

@@ -0,0 +1,55 @@
+<?php
+
+/**
+ * Joomla! Content Management System
+ *
+ * @copyright  (C) 2024 Open Source Matters, Inc. <https://www.joomla.org>
+ * @license    GNU General Public License version 2 or later; see LICENSE.txt
+ */
+
+namespace Joomla\CMS\Form\Rule;
+
+use Joomla\CMS\Form\Form;
+use Joomla\CMS\Form\FormRule;
+use Joomla\Registry\Registry;
+
+// phpcs:disable PSR1.Files.SideEffects
+\defined('_JEXEC') or die;
+// phpcs:enable PSR1.Files.SideEffects
+
+/**
+ * Form Rule class for the Joomla Platform.
+ *
+ * @since  __DEPLOY_VERSION__
+ */
+class RegexRule extends FormRule
+{
+    /**
+     * Method to test the value.
+     *
+     * @param   \SimpleXMLElement  $element  The SimpleXMLElement object representing the `<field>` tag for the form field object.
+     * @param   mixed              $value    The form field value to validate.
+     * @param   string             $group    The field name group control value. This acts as an array container for the field.
+     *                                       For example if the field has name="foo" and the group value is set to "bar" then the
+     *                                       full field name would end up being "bar[foo]".
+     * @param   ?Registry          $input    An optional Registry object with the entire data set to validate against the entire form.
+     * @param   ?Form              $form     The form object for which the field is being tested.
+     *
+     * @return  boolean  True if the value is valid, false otherwise.
+     *
+     * @since   __DEPLOY_VERSION__
+     * @throws  \UnexpectedValueException if rule is invalid.
+     */
+    public function test(\SimpleXMLElement $element, $value, $group = null, Registry $input = null, Form $form = null)
+    {
+        if ((string) $element['validate_regex']) {
+            $this->regex = (string) $element['validate_regex'];
+        }
+
+        if ((string) $element['validate_modifier']) {
+            $this->modifiers = (string) $element['validate_modifier'];
+        }
+
+        return parent::test($element, $value, $group, $input, $form);
+    }
+}