Issue #2658688 by slashrsm: Messages are not displayed in iFrame and …

…Modal displays

entity_browser.module

@@ -55,3 +55,27 @@ function entity_browser_form_alter(&$form, FormStateInterface &$form_state) {
     ];
   }
 }
+
+/**
+ * Implements hook_preprocess_page__entity_browser__iframe().
+ *
+ * Tries to figure out where messages block lives and display it separately.
+ */
+function entity_browser_preprocess_page__entity_browser__iframe(&$variables) {
+  $blocks = \Drupal::entityTypeManager()->getStorage('block')->loadByProperties([
+    'theme' => \Drupal::theme()->getActiveTheme()->getName(),
+    'plugin' => 'system_messages_block',
+  ]);
+  if ($messages = current($blocks)) {
+    $variables['messages'] = $variables['page'][$messages->getRegion()][$messages->id()];
+  }
+}
+
+/**
+ * Implements hook_preprocess_page__entity_browser__modal().
+ *
+ * Tries to figure out where messages block lives and display it separately.
+ */
+function entity_browser_preprocess_page__entity_browser__modal(&$variables) {
+  entity_browser_preprocess_page__entity_browser__iframe($variables);
+}

templates/page--entity-browser--iframe.html.twig

@@ -9,6 +9,15 @@
 #}
 <div class="layout-container">
 
+    {#
+      We ommit most of the regions in this template, which generally includes
+      messages too. Since this is not desired we try to figure out where messages
+      live and display them separately.
+
+      @see entity_browser_preprocess_page__entity_browser__iframe()
+    #}
+    {{ messages }}
+
     <main role="main">
         <a id="main-content" tabindex="-1"></a>{# link is in html.html.twig #}