Issue #2501655 by tim.plunkett, hchonov, willzyx:...

Issue #2501655 by tim.plunkett, hchonov, willzyx: ConfirmFormHelper::buildCancelLink() incorrectly handles ?destination URLs with a leading slash

core/lib/Drupal/Core/Form/ConfirmFormHelper.php

@@ -34,7 +34,7 @@ public static function buildCancelLink(ConfirmFormInterface $form, Request $requ
     if ($query->has('destination')) {
       $options = UrlHelper::parse($query->get('destination'));
       // @todo Revisit this in https://www.drupal.org/node/2418219.
-      $url = Url::fromUserInput('/' . $options['path'], $options);
+      $url = Url::fromUserInput('/' . ltrim($options['path'], '/'), $options);
     }
     // Check for a route-based cancel link.
     else {

core/tests/Drupal/Tests/Core/Form/ConfirmFormHelperTest.php

@@ -92,9 +92,11 @@ public function testCancelLinkRouteWithUrl() {
    * @covers ::buildCancelLink
    *
    * Tests a cancel link provided by the destination.
+   *
+   * @dataProvider providerTestCancelLinkDestination
    */
-  public function testCancelLinkDestination() {
-    $query = array('destination' => 'baz');
+  public function testCancelLinkDestination($destination) {
+    $query = array('destination' => $destination);
     $form = $this->getMock('Drupal\Core\Form\ConfirmFormInterface');
 
     $path_validator = $this->getMock('Drupal\Core\Path\PathValidatorInterface');
@@ -112,4 +114,14 @@ public function testCancelLinkDestination() {
     $this->assertSame($url, $link['#url']);
   }
 
+  /**
+   * Provides test data for testCancelLinkDestination().
+   */
+  public function providerTestCancelLinkDestination() {
+    $data = [];
+    $data[] = ['baz'];
+    $data[] = ['/baz'];
+    return $data;
+  }
+
 }