dev/core#2769 use php email validation not hacked qf

Per https://lab.civicrm.org/dev/core/-/issues/2769 we have had problems over the years with
quickform's email validation and we now have a hacked version that is
problematic from a maintenance pov & also doesn't work
with the string I have just encountered: name.-o-.i.10@example.com
(which I am told is valid and which passes the php filter).

We already have an email rule which calls a php native function
which is better maintained than our layers of hacks. This
PR registers our email rule - which overrides the quickform
one. If we merge this we can revert quickform back to
unhacked which will improve debugging
and maintenance (although it's actually bypassed
now with this change)

CRM/Core/Form.php

@@ -347,6 +347,7 @@ public function registerRules() {
       'settingPath',
       'autocomplete',
       'validContact',
+      'email',
     ];
 
     foreach ($rules as $rule) {

CRM/Utils/Rule.php

@@ -639,12 +639,46 @@ public static function boolean($value) {
    *
    * @return bool
    */
-  public static function email($value) {
+  public static function email($value): bool {
+    if (function_exists('idn_to_ascii')) {
+      $parts = explode('@', $value);
+      foreach ($parts as &$part) {
+        // if the function returns FALSE then let filter_var have at it.
+        $part = self::idnToAsci($part) ?: $part;
+        if ($part === 'localhost') {
+          // if we are in a dev environment add .com to trick it into accepting localhost.
+          // this is a bit best-effort - ie we don't really care that it's in a bigger if.
+          $part .= '.com';
+        }
+      }
+      $value = implode('@', $parts);
+    }
     return (bool) filter_var($value, FILTER_VALIDATE_EMAIL);
   }
 
   /**
-   * @param $list
+   * Convert domain string to ascii.
+   *
+   * See https://lab.civicrm.org/dev/core/-/issues/2769
+   * and also discussion over in guzzle land
+   * https://github.com/guzzle/guzzle/pull/2454
+   *
+   * @param string $string
+   *
+   * @return string|false
+   */
+  private static function idnToAsci(string $string) {
+    if (!\extension_loaded('intl')) {
+      return $string;
+    }
+    if (defined('INTL_IDNA_VARIANT_UTS46')) {
+      return idn_to_ascii($string, 0, INTL_IDNA_VARIANT_UTS46);
+    }
+    return idn_to_ascii($string);
+  }
+
+  /**
+   * @param string $list
    *
    * @return bool
    */

tests/phpunit/CRM/Utils/RuleTest.php

@@ -306,7 +306,8 @@ public function testCreditCardValidation($number, $type): void {
   }
 
   /**
-   * Test cvvs
+   * Test cvvs.
+   *
    * @return array
    */
   public static function cvvs(): array {
@@ -343,4 +344,30 @@ public function testCvvRule($cvv, $type, $expected): void {
     $this->assertEquals($expected, CRM_Utils_Rule::cvv($cvv, $type));
   }
 
+  /**
+   * Test CVV rule
+   *
+   * @param string $email
+   * @param bool $expected expected outcome of the rule validation
+   *
+   * @dataProvider emails
+   */
+  public function testEmailRule(string $email, bool $expected): void {
+    $this->assertEquals($expected, CRM_Utils_Rule::email($email));
+  }
+
+  /**
+   * Test emails.
+   *
+   * @return array
+   */
+  public static function emails(): array {
+    $cases = [];
+    $cases['name.-o-.i.10@example.com'] = ['name.-o-.i.10@example.com', TRUE];
+    $cases['test@ēxāmplē.co.nz'] = ['test@ēxāmplē.co.nz', TRUE];
+    $cases['test@localhost'] = ['test@localhost', TRUE];
+    $cases['test@ēxāmplē.co'] = ['test@exāmple', FALSE];
+    return $cases;
+  }
+
 }