Issue #2210755 by damiankloip, tim.plunkett: Add an area handler to display drupal_set_messages.

core/modules/views/lib/Drupal/views/Plugin/views/area/Messages.php

+<?php
+
+/**
+ * @file
+ * Contains \Drupal\views\Plugin\views\area\Messages.
+ */
+
+namespace Drupal\views\Plugin\views\area;
+
+/**
+ * Provides an area for messages.
+ *
+ * @ingroup views_area_handlers
+ *
+ * @PluginID("messages")
+ */
+class Messages extends AreaPluginBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function defineOptions() {
+    $options = parent::defineOptions();
+    // Set the default to TRUE so it shows on empty pages by default.
+    $options['empty']['default'] = TRUE;
+    return $options;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function render($empty = FALSE) {
+    if (!$empty || !empty($this->options['empty'])) {
+      return array(
+        '#theme' => 'status_messages',
+      );
+    }
+    return array();
+  }
+
+}

core/modules/views/tests/Drupal/views/Tests/Plugin/area/MessagesTest.php

+<?php
+
+/**
+ * @file
+ * Contains \Drupal\views\Tests\Plugin\area\MessagesTest.
+ */
+
+namespace Drupal\views\Tests\Plugin\area;
+
+use Drupal\Tests\UnitTestCase;
+use Drupal\views\Plugin\views\area\Messages;
+
+/**
+ * Tests the messages area handler
+ *
+ * @group Views
+ * @group Handlers
+ *
+ * @coversDefaultClass \Drupal\views\Plugin\views\area\Messages
+ */
+class MessagesTest extends UnitTestCase {
+
+  /**
+   * The view executable object.
+   *
+   * @var \Drupal\views\ViewExecutable
+   */
+  protected $view;
+
+  /**
+   * The message handler.
+   *
+   * @var \Drupal\views\Plugin\views\area\Messages
+   */
+  protected $messagesHandler;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getInfo() {
+    return array(
+      'name' => 'Area: Messages',
+      'description' => 'Tests the Drupal\views\Plugin\views\area\Messages handler.',
+      'group' => 'Views Handlers',
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setUp() {
+    parent::setUp();
+
+    $this->messagesHandler = new Messages(array(), 'result', array());
+  }
+
+  /**
+   * Tests the render method.
+   *
+   * @covers ::defineOptions()
+   * @covers ::render()
+   */
+  public function testRender() {
+    // The handler is configured to show with empty views by default, so should
+    // appear.
+    $this->assertSame(array('#theme' => 'status_messages'), $this->messagesHandler->render());
+
+    // Turn empty off, and make sure it isn't rendered.
+    $this->messagesHandler->options['empty'] = FALSE;
+    // $empty parameter passed to render will still be FALSE, so should still
+    // appear.
+    $this->assertSame(array('#theme' => 'status_messages'), $this->messagesHandler->render());
+    // Should now be empty as both the empty option and parameter are empty.
+    $this->assertSame(array(), $this->messagesHandler->render(TRUE));
+  }
+
+}

core/modules/views/views.views.inc

@@ -90,6 +90,14 @@ function views_views_data() {
     ),
   );
 
+  $data['views']['messages'] = array(
+    'title' => t('Messages'),
+    'help' => t('Displays messages in an area.'),
+    'area' => array(
+      'id' => 'messages',
+    ),
+  );
+
   $data['views']['http_status_code'] = array(
     'title' => t('Response status code'),
     'help' => t('Alter the HTTP response status code used by this view, mostly helpful for empty results.'),