Issue #2967567 by WalkingDexter, borisson_, catch, dawehner, Lendude: Views...

Issue #2967567 by WalkingDexter, borisson_, catch, dawehner, Lendude: Views display extenders validation

core/modules/views/src/Plugin/views/display/DisplayPluginBase.php

@@ -2479,6 +2479,14 @@ public function validate() {
       }
     }
 
+    // Validate extenders.
+    foreach ($this->extenders as $extender) {
+      $result = $extender->validate();
+      if (!empty($result) && is_array($result)) {
+        $errors = array_merge($errors, $result);
+      }
+    }
+
     return $errors;
   }
 

core/modules/views/tests/modules/views_test_data/src/Plugin/views/display_extender/DisplayExtenderTest3.php

+<?php
+
+namespace Drupal\views_test_data\Plugin\views\display_extender;
+
+/**
+ * Defines the third display extender test plugin.
+ *
+ * @ViewsDisplayExtender(
+ *   id = "display_extender_test_3",
+ *   title = @Translation("Display extender test number three")
+ * )
+ */
+class DisplayExtenderTest3 extends DisplayExtenderTest {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function validate() {
+    return ['Display extender test error.'];
+  }
+
+}

core/modules/views/tests/src/Kernel/Plugin/DisplayExtenderTest.php

@@ -42,4 +42,18 @@ public function testDisplayExtenders() {
     $this->assertTrue($display_extender->testState['query'], 'Make sure the display extender was able to react on query.');
   }
 
+  /**
+   * Test display extenders validation.
+   */
+  public function testDisplayExtendersValidate() {
+    $this->config('views.settings')->set('display_extenders', ['display_extender_test_3'])->save();
+
+    $view = Views::getView('test_view');
+    $errors = $view->validate();
+
+    foreach ($view->displayHandlers as $id => $display) {
+      $this->assertTrue(isset($errors[$id]) && in_array('Display extender test error.', $errors[$id]), format_string('Error message found for @id display', ['@id' => $id]));
+    }
+  }
+
 }