Issue #2999549 by mtift, Daniel Korte, mherchel, alexpott, larowlan: Allow button tag in LinkGenerator for better accessibility

(cherry picked from commit 8ed835c0bc)

core/lib/Drupal/Core/GeneratedButton.php

@@ -0,0 +1,19 @@
+<?php
+
+namespace Drupal\Core;
+
+/**
+ * This class holds a <button> generated from the <button> route.
+ *
+ * Unlike \Drupal\Core\Render\Element\Button, this is not for generating
+ * buttons for forms. This class is for putting a button in a list of links
+ * such as a multi-level menu.
+ */
+class GeneratedButton extends GeneratedLink {
+
+  /**
+   * {@inheritdoc}
+   */
+  const TAG = 'button';
+
+}

core/lib/Drupal/Core/Utility/LinkGenerator.php

@@ -7,6 +7,7 @@ use Drupal\Component\Utility\Html;
 use Drupal\Component\Render\MarkupInterface;
 use Drupal\Core\Extension\ModuleHandlerInterface;
 use Drupal\Core\GeneratedLink;
+use Drupal\Core\GeneratedButton;
 use Drupal\Core\GeneratedNoLink;
 use Drupal\Core\Link;
 use Drupal\Core\Render\RendererInterface;
@@ -165,19 +166,41 @@ class LinkGenerator implements LinkGeneratorInterface {
     if ($url->isExternal()) {
       $generated_link = new GeneratedLink();
       $attributes['href'] = $url->toString(FALSE);
+      return $this->doGenerate($generated_link, $attributes, $variables);
     }
-    elseif ($url->isRouted() && $url->getRouteName() === '<nolink>') {
+    if ($url->isRouted() && $url->getRouteName() === '<nolink>') {
       $generated_link = new GeneratedNoLink();
       unset($attributes['href']);
+      return $this->doGenerate($generated_link, $attributes, $variables);
     }
-    else {
-      $generated_url = $url->toString(TRUE);
-      $generated_link = GeneratedLink::createFromObject($generated_url);
-      // The result of the URL generator is a plain-text URL to use as the href
-      // attribute, and it is escaped by \Drupal\Core\Template\Attribute.
-      $attributes['href'] = $generated_url->getGeneratedUrl();
+    if ($url->isRouted() && $url->getRouteName() === '<button>') {
+      $generated_link = new GeneratedButton();
+      $attributes['type'] = 'button';
+      unset($attributes['href']);
+      return $this->doGenerate($generated_link, $attributes, $variables);
     }
+    $generated_url = $url->toString(TRUE);
+    $generated_link = GeneratedLink::createFromObject($generated_url);
+    // The result of the URL generator is a plain-text URL to use as the href
+    // attribute, and it is escaped by \Drupal\Core\Template\Attribute.
+    $attributes['href'] = $generated_url->getGeneratedUrl();
+    return $this->doGenerate($generated_link, $attributes, $variables);
+  }
 
+  /**
+   * Generates the link.
+   *
+   * @param Drupal\Core\GeneratedLink $generated_link
+   *   The generated link, along with its associated cacheability metadata.
+   * @param array $attributes
+   *   The attributes of the generated link.
+   * @param array $variables
+   *   The link text, url, and other options.
+   *
+   * @return Drupal\Core\GeneratedLink
+   *   The generated link, along with its associated cacheability metadata.
+   */
+  protected function doGenerate($generated_link, $attributes, $variables) {
     if (!($variables['text'] instanceof MarkupInterface)) {
       $variables['text'] = Html::escape($variables['text']);
     }

core/modules/system/system.routing.yml

@@ -412,6 +412,13 @@ system.theme_settings_theme:
   requirements:
     _access: 'TRUE'
 
+'<button>':
+  path: ''
+  options:
+    _no_path: TRUE
+  requirements:
+    _access: 'TRUE'
+
 '<current>':
   path: '<current>'
 

core/tests/Drupal/Tests/Core/Utility/LinkGeneratorTest.php

@@ -3,6 +3,7 @@
 namespace Drupal\Tests\Core\Utility;
 
 use Drupal\Component\Render\MarkupInterface;
+use Drupal\Core\GeneratedButton;
 use Drupal\Core\GeneratedNoLink;
 use Drupal\Core\GeneratedUrl;
 use Drupal\Core\Language\Language;
@@ -199,6 +200,26 @@ class LinkGeneratorTest extends UnitTestCase {
     $this->assertSame('<a href="">Test</a>', (string) $result);
   }
 
+  /**
+   * Tests the generate() method with the <button> route.
+   *
+   * @covers ::generate
+   */
+  public function testGenerateButton() {
+    $this->urlGenerator->expects($this->never())
+      ->method('generateFromRoute');
+    $this->moduleHandler->expects($this->once())
+      ->method('alter')
+      ->with('link', $this->isType('array'));
+
+    $url = Url::fromRoute('<button>');
+    $url->setUrlGenerator($this->urlGenerator);
+
+    $result = $this->linkGenerator->generate('Test', $url);
+    $this->assertTrue($result instanceof GeneratedButton);
+    $this->assertSame('<button type="button">Test</button>', (string) $result);
+  }
+
   /**
    * Tests the generate() method with an external URL.
    *