commit aebe033a3f500996dd53cdaed9857e96f60adcc0
Author: Joel Pittet <joel@pittet.ca>
Date:   Wed May 7 23:08:08 2014 -0700

    leave arrays as arrays and booleans as booleans, ftw!

diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index 5bfac2e..a2a333d 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -2252,14 +2252,12 @@ function template_preprocess_maintenance_page(&$variables) {
   template_preprocess_page($variables);
 
   $page_object = $variables['page']['#page'];
-  $attributes = $page_object->getBodyAttributes();
-  $classes = $attributes['class'];
-  $classes[] = 'maintenance-page';
-  $classes[] = 'in-maintenance';
+  $variables['attributes'] = $page_object->getBodyAttributes();
+  $variables['attributes']['class'][] = 'maintenance-page';
+  $variables['attributes']['class'][] = 'in-maintenance';
   if (isset($variables['db_is_active']) && !$variables['db_is_active']) {
-    $classes[] = 'db-offline';
+    $variables['attributes']['class'][] = 'db-offline';
   }
-  $attributes['class'] = $classes;
 
   // @see system_page_build()
   $attached = array(
@@ -2288,10 +2286,8 @@ function template_preprocess_install_page(&$variables) {
   template_preprocess_maintenance_page($variables);
 
   $page_object = $variables['page']['#page'];
-  $attributes = $page_object->getBodyAttributes();
-  $classes = $attributes['class'];
-  $classes[] = 'install-page';
-  $attributes['class'] = $classes;
+  $variables['attributes'] = $page_object->getBodyAttributes();
+  $variables['attributes']['class'][] = 'install-page';
 
   // Override the site name that is displayed on the page, since Drupal is
   // still in the process of being installed.
diff --git a/core/lib/Drupal/Core/Template/Attribute.php b/core/lib/Drupal/Core/Template/Attribute.php
index d2fa8bb..c3b3ad6 100644
--- a/core/lib/Drupal/Core/Template/Attribute.php
+++ b/core/lib/Drupal/Core/Template/Attribute.php
@@ -34,27 +34,15 @@
 class Attribute extends \ArrayObject {
 
   /**
-   * Constructor
-   *
-   * Enforces that we have an array, and enforces parameter access to array
-   * elements.
-   *
-   * @param  array $values
-   */
-  public function __construct(array $values = null) {
-    if (null === $values) {
-      $values = array();
-    }
-    parent::__construct($values, \ArrayObject::ARRAY_AS_PROPS);
-  }
-
-  /**
    * Implements the magic __toString() method.
    */
   public function __toString() {
     $return = '';
     foreach ($this as $name => $value) {
       $rendered = NULL;
+      if ($value === NULL) {
+        continue;
+      }
       $name = String::checkPlain($name);
       if (is_array($value)) {
         $rendered = $name . '="' . String::checkPlain(implode(' ', $value)) . '"';
@@ -71,25 +59,4 @@ public function __toString() {
     }
     return $return;
   }
-
-  /**
-   * Implements the magic __call() method.
-   */
-  public function __call($name, $arguments) {
-    $rendered = NULL;
-    if (isset($this[$name])) {
-      $value = $this[$name];
-      if (is_array($value)) {
-        $rendered = String::checkPlain(implode(' ', $value));
-      }
-      elseif (is_bool($value)) {
-        $rendered = ($value === FALSE) ? NULL : $name;
-      }
-      else {
-        $rendered = String::checkPlain($value);
-      }
-    }
-    return $rendered;
-  }
-
 }
diff --git a/core/modules/comment/comment.module b/core/modules/comment/comment.module
index 9cc9a8b..2080fa4 100644
--- a/core/modules/comment/comment.module
+++ b/core/modules/comment/comment.module
@@ -437,7 +437,7 @@ function comment_node_links_alter(array &$node_links, NodeInterface $node, array
                 'title' => '',
                 'href' => '',
                 'attributes' => array(
-                  'class' => 'hidden',
+                  'class' => array('hidden'),
                   'title' => t('Jump to the first new comment of this posting.'),
                   'data-history-node-last-comment-timestamp' => $node->get($field_name)->last_comment_timestamp,
                   'data-history-node-field-name' => $field_name,
diff --git a/core/modules/node/templates/node.html.twig b/core/modules/node/templates/node.html.twig
index ae1162e..c19db96 100644
--- a/core/modules/node/templates/node.html.twig
+++ b/core/modules/node/templates/node.html.twig
@@ -75,7 +75,7 @@
  * @ingroup themeable
  */
 #}
-<article id="node-{{ node.id }}" class="{{ attributes.class }} clearfix"{{ attributes|without('id', 'class') }}>
+<article id="node-{{ node.id }}" class="{{ attributes.class|merge(['clearfix'])|join(' ') }}"{{ attributes|without('id', 'class') }}>
 
   {{ title_prefix }}
   {% if not page %}
diff --git a/core/modules/system/tests/modules/twig_theme_test/templates/twig_theme_test.filter.html.twig b/core/modules/system/tests/modules/twig_theme_test/templates/twig_theme_test.filter.html.twig
index 28e5c15..c292ca1 100644
--- a/core/modules/system/tests/modules/twig_theme_test/templates/twig_theme_test.filter.html.twig
+++ b/core/modules/system/tests/modules/twig_theme_test/templates/twig_theme_test.filter.html.twig
@@ -13,10 +13,10 @@
   </blockquote>
 </div>
 <div><span{{ attributes }}>All attributes:</span></div>
-<div><span class="{{ attributes.class }}"{{ attributes|without('class') }}>Class attributes in front, remainder at the back:</span></div>
-<div><span{{ attributes|without('class') }} data-class="{{ attributes.class }}">Class attributes in back, remainder at the front:</span></div>
-<div><span class="{{ attributes.class }}">Class attributes only:</span></div>
-<div><span {{ attributes.checked }}{{ attributes|without('checked') }}>Without boolean attribute.</span></div>
+<div><span class="{{ attributes.class|join(' ') }}"{{ attributes|without('class') }}>Class attributes in front, remainder at the back:</span></div>
+<div><span{{ attributes|without('class') }} data-class="{{ attributes.class|join(' ') }}">Class attributes in back, remainder at the front:</span></div>
+<div><span class="{{ attributes.class|join(' ') }}">Class attributes only:</span></div>
+<div><span{{ attributes.checked ? ' checked' }}{{ attributes|without('checked') }}>Without boolean attribute.</span></div>
 <div><span data-id="{{ attributes.id }}"{{ attributes|without('id') }}>Without string attribute.</span></div>
 <div><span{{ attributes|without('id', 'class') }}>Without either nor class attributes.</span></div>
 <div><span{{ attributes }}>All attributes again.</span></div>
diff --git a/core/themes/bartik/templates/comment.html.twig b/core/themes/bartik/templates/comment.html.twig
index d2c4584..b034351 100644
--- a/core/themes/bartik/templates/comment.html.twig
+++ b/core/themes/bartik/templates/comment.html.twig
@@ -62,7 +62,7 @@
  * @see template_preprocess_comment()
  */
 #}
-<article class="{{ attributes.class }} clearfix" role="article"{{ attributes|without('class', 'role') }}>
+<article class="{{ attributes.class|merge(['clearfix'])|join(' ') }}" role="article"{{ attributes|without('class', 'role') }}>
 
   <header class="comment-header">
     <div class="attribution">
diff --git a/core/themes/bartik/templates/field--taxonomy-term-reference.html.twig b/core/themes/bartik/templates/field--taxonomy-term-reference.html.twig
index fad1ed7..40545cc 100644
--- a/core/themes/bartik/templates/field--taxonomy-term-reference.html.twig
+++ b/core/themes/bartik/templates/field--taxonomy-term-reference.html.twig
@@ -16,7 +16,7 @@
  * @see bartik_preprocess_field()
  */
 #}
-<div class="{{ attributes.class }} clearfix"{{ attributes|without('class') }}>
+<div class="{{ attributes.class|merge(['clearfix'])|join(' ') }}"{{ attributes|without('class') }}>
   <h3{{ label_attributes }}>{{ label }}: </h3>
   <ul class="links">
     {% for delta, item in items %}
diff --git a/core/themes/bartik/templates/node.html.twig b/core/themes/bartik/templates/node.html.twig
index 2848899..214c222 100644
--- a/core/themes/bartik/templates/node.html.twig
+++ b/core/themes/bartik/templates/node.html.twig
@@ -69,7 +69,7 @@
  * @see template_preprocess_node()
  */
 #}
-<article id="node-{{ node.id }}" class="{{ attributes.class }} clearfix" role="article"{{ attributes|without('id', 'class', 'role') }}>
+<article id="node-{{ node.id }}" class="{{ attributes.class|merge(['clearfix'])|join(' ') }}" role="article"{{ attributes|without('id', 'class', 'role') }}>
 
   <header>
     {{ title_prefix }}
diff --git a/core/themes/seven/seven.theme b/core/themes/seven/seven.theme
index b337c10..313242b 100644
--- a/core/themes/seven/seven.theme
+++ b/core/themes/seven/seven.theme
@@ -15,15 +15,15 @@ use Drupal\Component\Utility\String;
 function seven_preprocess_page(&$variables) {
   /** @var \Drupal\Core\Page\HtmlPage $page_object */
   $page_object = $variables['page']['#page'];
-  $attributes = $page_object->getBodyAttributes();
+  $variables['attributes'] = $page_object->getBodyAttributes();
 
   // Add information about the number of sidebars.
   if (!empty($variables['page']['sidebar_first'])) {
-    $attributes['class'][] = 'one-sidebar';
-    $attributes['class'][] = 'sidebar-first';
+    $variables['attributes']['class'][] = 'one-sidebar';
+    $variables['attributes']['class'][] = 'sidebar-first';
   }
   else {
-    $attributes['class'][] = 'no-sidebars';
+    $variables['attributes']['class'][] = 'no-sidebars';
   }
 
   $variables['primary_local_tasks'] = $variables['tabs'];
@@ -269,10 +269,8 @@ function seven_element_info_alter(&$type) {
  */
 function seven_preprocess_install_page(&$variables) {
   $page_object = $variables['page']['#page'];
-  $attributes = $page_object->getHtmlAttributes();
-  $classes = $attributes['class'];
-  $classes[] = 'install-background';
-  $attributes['class'] = $classes;
+  $variables['attributes'] = $page_object->getHtmlAttributes();
+  $variables['attributes']['class'][] = 'install-background';
 
   // Normally we could attach libraries via hook_page_alter(), but when the
   // database is inactive it's not called so we add them here.
@@ -292,10 +290,8 @@ function seven_preprocess_install_page(&$variables) {
  */
 function seven_preprocess_maintenance_page(&$variables) {
   $page_object = $variables['page']['#page'];
-  $attributes = $page_object->getHtmlAttributes();
-  $classes = $attributes['class'];
-  $classes[] = 'maintenance-background';
-  $attributes['class'] = $classes;
+  $variables['attributes'] = $page_object->getHtmlAttributes();
+  $variables['attributes']['class'][] = 'maintenance-background';
 
   // // Normally we could attach libraries via hook_page_alter(), but when the
   // // database is inactive it's not called so we add them here.