Issue #3099662 by jibran, dpi, jptaranto, larowlan, nod_: Allow...

Issue #3099662 by jibran, dpi, jptaranto, larowlan, nod_: Allow ckeditor_stylesheets to refer to a Drupal root URL

core/modules/ckeditor/ckeditor.module

@@ -89,9 +89,15 @@ function _ckeditor_theme_css($theme = NULL) {
     if (isset($info['ckeditor_stylesheets'])) {
       $css = $info['ckeditor_stylesheets'];
       foreach ($css as $key => $url) {
+        // CSS url is external.
         if (UrlHelper::isExternal($url)) {
           $css[$key] = $url;
         }
+        // CSS url is relative to Drupal root.
+        elseif ($url[0] === '/') {
+          $css[$key] = substr($url, 1);
+        }
+        // CSS url is relative to theme.
         else {
           $css[$key] = $theme_path . '/' . $url;
         }

core/modules/ckeditor/tests/src/Functional/CKEditorLoadingTest.php

@@ -242,6 +242,14 @@ public function testExternalStylesheets() {
       'core/modules/system/tests/themes/test_ckeditor_stylesheets_relative/css/yokotsoko.css',
     ];
     $this->assertIdentical($expected, _ckeditor_theme_css('test_ckeditor_stylesheets_relative'));
+
+    // Case 4: Install theme which has a Drupal root CSS URL.
+    $theme_installer->install(['test_ckeditor_stylesheets_drupal_root']);
+    $this->config('system.theme')->set('default', 'test_ckeditor_stylesheets_drupal_root')->save();
+    $expected = [
+      'core/modules/system/tests/themes/test_ckeditor_stylesheets_drupal_root/css/yokotsoko.css',
+    ];
+    $this->assertIdentical($expected, _ckeditor_theme_css('test_ckeditor_stylesheets_drupal_root'));
   }
 
   protected function getThingsToCheck() {

core/modules/system/tests/themes/test_ckeditor_stylesheets_drupal_root/css/yokotsoko.css

+/**
+ * @file
+ * Test CSS asset file for test_ckeditor_stylesheets_drupal_root.theme.
+ */

core/modules/system/tests/themes/test_ckeditor_stylesheets_drupal_root/test_ckeditor_stylesheets_drupal_root.info.yml

+name: Test Drupal root CKEditor stylesheets
+type: theme
+description: 'A theme that uses a Drupal root CKEditor stylesheet.'
+package: Testing
+version: VERSION
+base theme: false
+
+ckeditor_stylesheets:
+  - /core/modules/system/tests/themes/test_ckeditor_stylesheets_drupal_root/css/yokotsoko.css