Issue #2534780 by olli, dawehner: Fatal error rendering fields using an optional relationship

core/modules/views/src/Entity/Render/EntityFieldRenderer.php

@@ -138,13 +138,18 @@ public function render(ResultRow $row, Field $field = NULL) {
         $build = $this->build[$row->index][$field_id];
         unset($this->build[$row->index][$field_id]);
       }
-      else {
+      elseif (isset($this->build[$row->index])) {
         // In the uncommon case where a field gets rendered several times
         // (typically through direct Views API calls), the pre-computed render
         // array was removed by the unset() above. We have to manually rebuild
         // the render array for the row.
         $build = $this->buildFields([$row])[$row->index][$field_id];
       }
+      else {
+        // In case the relationship is optional, there might not be any fields
+        // to render for this row.
+        $build = [];
+      }
     }
     else {
       // Same logic as above, in the case where we are being called for a whole
@@ -199,8 +204,9 @@ protected function buildFields(array $values) {
       $entities_by_bundles = [];
       $field = $this->view->field[current($field_ids)];
       foreach ($values as $result_row) {
-        $entity = $field->getEntity($result_row);
-        $entities_by_bundles[$entity->bundle()][$result_row->index] = $this->getEntityTranslation($entity, $result_row);
+        if ($entity = $field->getEntity($result_row)) {
+          $entities_by_bundles[$entity->bundle()][$result_row->index] = $this->getEntityTranslation($entity, $result_row);
+        }
       }
 
       // Determine unique sets of fields that can be processed by the same

core/modules/views/src/Plugin/views/field/FieldPluginBase.php

@@ -395,7 +395,7 @@ public function getEntity(ResultRow $values) {
     if ($relationship_id == 'none') {
       return $values->_entity;
     }
-    else {
+    elseif (isset($values->_relationship_entities[$relationship_id])) {
       return $values->_relationship_entities[$relationship_id];
     }
   }

core/modules/views/src/Tests/Handler/RelationshipTest.php

@@ -7,8 +7,8 @@
 
 namespace Drupal\views\Tests\Handler;
 
+use Drupal\simpletest\UserCreationTrait;
 use Drupal\views\Views;
-use Drupal\views\Tests\ViewUnitTestBase;
 use Drupal\views\Tests\Plugin\RelationshipJoinTestBase;
 
 /**
@@ -18,6 +18,7 @@
  * @see \Drupal\views\Plugin\views\relationship\RelationshipPluginBase
  */
 class RelationshipTest extends RelationshipJoinTestBase {
+  use UserCreationTrait;
 
   /**
    * Views used by this test.
@@ -133,4 +134,51 @@ public function testRelationshipQuery() {
     $this->assertIdenticalResultset($view, $expected_result, $this->columnMap);
   }
 
+  /**
+   * Tests rendering of a view with a relationship.
+   */
+  public function testRelationshipRender() {
+    $author1 = $this->createUser();
+    db_query("UPDATE {views_test_data} SET uid = :uid WHERE id = 1", [':uid' => $author1->id()]);
+    $author2 = $this->createUser();
+    db_query("UPDATE {views_test_data} SET uid = :uid WHERE id = 2", [':uid' => $author2->id()]);
+    // Set uid to non-existing author uid for row 3.
+    db_query("UPDATE {views_test_data} SET uid = :uid WHERE id = 3", [':uid' => $author2->id() + 123]);
+
+    $view = Views::getView('test_view');
+    // Add a relationship for authors.
+    $view->getDisplay()->overrideOption('relationships', [
+      'uid' => [
+        'id' => 'uid',
+        'table' => 'views_test_data',
+        'field' => 'uid',
+      ],
+    ]);
+    // Add fields for {views_test_data}.id and author name.
+    $view->getDisplay()->overrideOption('fields', [
+      'id' => [
+        'id' => 'id',
+        'table' => 'views_test_data',
+        'field' => 'id',
+      ],
+      'author' => [
+        'id' => 'author',
+        'table' => 'users_field_data',
+        'field' => 'name',
+        'relationship' => 'uid',
+      ],
+    ]);
+
+    // Render the view.
+    $output = $view->preview();
+    $html = $this->container->get('renderer')->renderRoot($output);
+    $this->setRawContent($html);
+
+    // Check that the output contains correct values.
+    $xpath = '//div[@class="views-row" and div[@class="views-field views-field-id"]=:id and div[@class="views-field views-field-author"]=:author]';
+    $this->assertEqual(1, count($this->xpath($xpath, [':id' => 1, ':author' => $author1->getUsername()])));
+    $this->assertEqual(1, count($this->xpath($xpath, [':id' => 2, ':author' => $author2->getUsername()])));
+    $this->assertEqual(1, count($this->xpath($xpath, [':id' => 3, ':author' => ''])));
+  }
+
 }