Issue #2887860 by drumm, Cottser: Allow attributes to be passed to admin...

Issue #2887860 by drumm, Cottser: Allow attributes to be passed to admin blocks (admin_block theme hook)

core/modules/system/system.module

@@ -250,7 +250,7 @@ function system_theme() {
       'file' => 'system.admin.inc',
     ],
     'admin_block' => [
-      'variables' => ['block' => NULL],
+      'variables' => ['block' => NULL, 'attributes' => []],
       'file' => 'system.admin.inc',
     ],
     'admin_block_content' => [

core/modules/system/templates/admin-block.html.twig

@@ -10,11 +10,17 @@
  *   - content: (optional) The content of the block.
  *   - description: (optional) A description of the block.
  *     (Description should only be output if content is not available).
+ * - attributes: HTML attributes for the containing div element.
  *
  * @ingroup themeable
  */
 #}
-<div class="panel">
+{%
+  set classes = [
+    'panel',
+  ]
+%}
+<div{{ attributes.addClass(classes) }}>
   {% if block.title %}
     <h3 class="panel__title">{{ block.title }}</h3>
   {% endif %}

core/themes/seven/seven.libraries.yml

@@ -10,7 +10,6 @@ global-styling:
       css/components/content-header.css: {}
       css/components/breadcrumb.css: {}
       css/components/buttons.css: {}
-      css/components/colors.css: {}
       css/components/messages.css: {}
       css/components/dropbutton.component.css: {}
       css/components/entity-meta.css: {}
@@ -33,6 +32,8 @@ global-styling:
       css/components/system-status-counter.css: {}
       css/components/tabs.css: {}
       css/components/views-ui.css: {}
+    theme:
+      css/theme/colors.css: {}
     layout:
       css/layout/layout.css: {}
   dependencies:

core/themes/stable/templates/admin/admin-block.html.twig

@@ -10,9 +10,15 @@
  *   - content: (optional) The content of the block.
  *   - description: (optional) A description of the block.
  *     (Description should only be output if content is not available).
+ * - attributes: HTML attributes for the containing div element.
  */
 #}
-<div class="panel">
+{%
+  set classes = [
+    'panel',
+  ]
+%}
+<div{{ attributes.addClass(classes) }}>
   {% if block.title %}
     <h3 class="panel__title">{{ block.title }}</h3>
   {% endif %}