url-generator-host-option.patch

diff --git a/core/lib/Drupal/Core/Routing/UrlGenerator.php b/core/lib/Drupal/Core/Routing/UrlGenerator.php
index 9979b73..3dce650 100644
--- a/core/lib/Drupal/Core/Routing/UrlGenerator.php
+++ b/core/lib/Drupal/Core/Routing/UrlGenerator.php
@@ -340,7 +340,10 @@ public function generateFromRoute($name, $parameters = array(), $options = array
     $base_url = $this->context->getBaseUrl();
 
     $absolute = !empty($options['absolute']);
-    if (!$absolute || !$host = $this->context->getHost()) {
+
+    $host = isset($options['host']) && strlen((string) $options['host']) > 0 ? (string) $options['host'] : $this->context->getHost();
+
+    if (!$absolute || !$host) {
       $url = $base_url . $path . $fragment;
       return $collect_bubbleable_metadata ? $generated_url->setGeneratedUrl($url) : $url;
     }
diff --git a/core/tests/Drupal/Tests/Core/Routing/UrlGeneratorTest.php b/core/tests/Drupal/Tests/Core/Routing/UrlGeneratorTest.php
index 4d91218..6a0fcc5 100644
--- a/core/tests/Drupal/Tests/Core/Routing/UrlGeneratorTest.php
+++ b/core/tests/Drupal/Tests/Core/Routing/UrlGeneratorTest.php
@@ -410,4 +410,14 @@ protected function assertGenerateFromRoute($route_name, array $route_parameters,
     $this->assertEquals($expected_bubbleable_metadata, BubbleableMetadata::createFromObject($generated_url));
   }
 
+  /**
+   * Confirms that URL generation works with `host` option specified.
+   */
+  public function testUrlGenerationWithHostOption() {
+
+    $options = array('absolute' => TRUE, 'fragment' => 'top', 'host' => 'local.dev');
+    // Extra parameters should appear in the query string.
+    $this->assertGenerateFromRoute('test_1', ['zoo' => 5], $options, 'http://local.dev/hello/world?zoo=5#top', (new BubbleableMetadata())->setCacheMaxAge(Cache::PERMANENT)->setCacheContexts(['url.site']));
+  }
+
 }