Unable to render link with attributes twice

@webflo, I'm quite curious what removed the attributes, this solution could work but maybe better if we find where the attributes are being removed because that may have other negative effects elsewhere in the system?

This is a unit test which renders the link twice. Its a bug in the underlying link generator.

Related bug ... #2847611: \Drupal\Core\Template\TwigExtension::getLink overrides existing classes

@jorges and @dawehner debugged the remaining failure. Turns out, we need the original fix from @webflo as well.

This time with less commented out.

+++ b/core/lib/Drupal/Core/Template/TwigExtension.php
@@ -280,6 +280,10 @@ public function getLink($text, $url, $attributes = []) {
+    // The twig extension should not modify the original url object, this

+++ b/core/lib/Drupal/Core/Utility/LinkGenerator.php
@@ -76,6 +76,11 @@ public function generateFromLink(Link $link) {
+    // The link generator should not modify the original url object, this

Nit, s/url/URL

Fix looks good.

Url should so be immutable.

Committed and pushed 9c77748 to 8.4.x and 91d653d to 8.3.x. Thanks!

diff --git a/core/lib/Drupal/Core/Template/TwigExtension.php b/core/lib/Drupal/Core/Template/TwigExtension.php
index ed2b4c0..9f25959 100644
--- a/core/lib/Drupal/Core/Template/TwigExtension.php
+++ b/core/lib/Drupal/Core/Template/TwigExtension.php
@@ -280,7 +280,7 @@ public function getLink($text, $url, $attributes = []) {
     if (!$url instanceof Url) {
       $url = Url::fromUri($url);
     }
-    // The twig extension should not modify the original url object, this
+    // The twig extension should not modify the original URL object, this
     // ensures consistent rendering.
     // @see https://www.drupal.org/node/2842399
     $url = clone $url;
diff --git a/core/lib/Drupal/Core/Utility/LinkGenerator.php b/core/lib/Drupal/Core/Utility/LinkGenerator.php
index ed022a6..1dad742 100644
--- a/core/lib/Drupal/Core/Utility/LinkGenerator.php
+++ b/core/lib/Drupal/Core/Utility/LinkGenerator.php
@@ -76,7 +76,7 @@ public function generateFromLink(Link $link) {
    * @see system_page_attachments()
    */
   public function generate($text, Url $url) {
-    // The link generator should not modify the original url object, this
+    // The link generator should not modify the original URL object, this
     // ensures consistent rendering.
     // @see https://www.drupal.org/node/2842399
     $url = clone $url;

Fixed on commit.