interdiff impossible; taking evasive action
reverted:
--- b/src/Plugin/Field/FieldType/ViewsReferenceItem.php
+++ a/src/Plugin/Field/FieldType/ViewsReferenceItem.php
@@ -140,18 +140,6 @@
     return $form;
   }
 
-  /**
-   * {@inheritdoc}
-   */
-  public static function fieldSettingsFormValidate(array $form, FormStateInterface $form_state) {
-    // Remove unchecked values. so that we have only the checked values in the config.
-    $keys = ['plugin_types', 'preselect_views', 'enabled_settings'];
-    foreach ($keys as $key) {
-      $form_state->setValue(['settings', $key], array_filter($form_state->getValue(['settings', $key], [])));
-    }
-    parent::fieldSettingsFormValidate($form, $form_state);
-  }
-
   /**
    * {@inheritdoc}
    */
unchanged:
--- a/src/Plugin/Field/FieldType/ViewsReferenceItem.php
+++ b/src/Plugin/Field/FieldType/ViewsReferenceItem.php
@@ -148,6 +148,20 @@ class ViewsReferenceItem extends EntityReferenceItem {
     return $form;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public static function fieldSettingsFormValidate(array $form, FormStateInterface $form_state) {
+    // Remove unchecked values. so that we have only the checked values in the
+    // config.
+    $keys = ['plugin_types', 'preselect_views', 'enabled_settings'];
+    foreach ($keys as $key) {
+      $path = ['settings', $key];
+      $form_state->setValue($path, array_filter($form_state->getValue($path, [])));
+    }
+    parent::fieldSettingsFormValidate($form, $form_state);
+  }
+
   /**
    * {@inheritdoc}
    */
diff -u b/tests/src/Functional/Update/ViewsReferenceUpdateTest.php b/tests/src/Functional/Update/ViewsReferenceUpdateTest.php
--- b/tests/src/Functional/Update/ViewsReferenceUpdateTest.php
+++ b/tests/src/Functional/Update/ViewsReferenceUpdateTest.php
@@ -1,5 +1,7 @@
-<?php declare(strict_types=1);
+<?php
 
+declare(strict_types=1);
+
 namespace Drupal\Tests\viewsreference\Functional\Update;
 
 use Drupal\FunctionalTests\Update\UpdatePathTestBase;
@@ -24,25 +26,29 @@
      * data: a:1:{s:9:"view_mode";s:12:"preview_wide";}
      */
     $this->databaseDumpFiles = [
-      __DIR__ . '/../../../fixtures/update/drupal-8.9.6.viewsreference-8.x-1.4.php.gz'
+      __DIR__ . '/../../../fixtures/update/drupal-8.9.6.viewsreference-8.x-1.4.php.gz',
     ];
   }
 
+  /**
+   * Tests the update hook 8103.
+   */
   public function testUpdateHook8103() {
     $columns = ['field_viewsreference_argument', 'field_viewsreference_title'];
     $connection = $this->container->get('database');
     /** @var \Drupal\Core\Database\Schema $schema */
     $schema = $connection->schema();
-    foreach($columns as $column) {
+    foreach ($columns as $column) {
       self::assertTrue($schema->fieldExists('node__field_viewsreference', $column));
     }
 
     $query = $connection->select('node__field_viewsreference', 'vr');
     $query->addField('vr', 'field_viewsreference_data');
     $result = $query->execute();
+    // @phpcs:ignore
     $data = unserialize($result->fetchField(), ['allowed_class' => FALSE]);
 
-    self::assertTrue(array_key_exists('view_mode', $data) && $data['view_mode'] === 'preview_wide');
+    self::assertTrue(array_key_exists('view_mode', $data) && 'preview_wide' === $data['view_mode']);
     self::assertArrayNotHasKey('title', $data);
     self::assertArrayNotHasKey('argument', $data);
 
@@ -51,16 +57,17 @@
     $this->runUpdates();
 
     $this->assertEqual(drupal_get_installed_schema_version('viewsreference'), 8103);
-    foreach($columns as $column) {
+    foreach ($columns as $column) {
       self::assertFalse($schema->fieldExists('node__field_viewsreference', $column));
     }
     $query = $connection->select('node__field_viewsreference', 'vr');
     $query->addField('vr', 'field_viewsreference_data');
     $result = $query->execute();
+    // @phpcs:ignore
     $data = unserialize($result->fetchField(), ['allowed_class' => FALSE]);
-    self::assertTrue(array_key_exists('view_mode', $data) && $data['view_mode'] === 'preview_wide');
-    self::assertTrue(array_key_exists('title', $data) && $data['title'] === '1');
-    self::assertTrue(array_key_exists('argument', $data) && $data['argument'] === 'test');
+    self::assertTrue(array_key_exists('view_mode', $data) && 'preview_wide' === $data['view_mode']);
+    self::assertTrue(array_key_exists('title', $data) && '1' === $data['title']);
+    self::assertTrue(array_key_exists('argument', $data) && 'test' === $data['argument']);
   }
 
 }
diff -u b/viewsreference.install b/viewsreference.install
--- b/viewsreference.install
+++ b/viewsreference.install
@@ -33,15 +33,15 @@
  * Migrate title and argument columns to the new data field.
  */
 function viewsreference_update_8103() {
-  $field_type           = 'viewsreference';
-  $entity_type_manager  = \Drupal::entityTypeManager();
+  $field_type = 'viewsreference';
+  $entity_type_manager = \Drupal::entityTypeManager();
   /** @var \Drupal\Core\Entity\EntityFieldManagerInterface $entity_field_manager */
   $entity_field_manager = \Drupal::service('entity_field.manager');
-  $entity_field_map     = $entity_field_manager->getFieldMapByFieldType($field_type);
-  $database             = \Drupal::database();
-  $entity_def_manager   = \Drupal::entityDefinitionUpdateManager();
+  $entity_field_map = $entity_field_manager->getFieldMapByFieldType($field_type);
+  $database = \Drupal::database();
+  $entity_def_manager = \Drupal::entityDefinitionUpdateManager();
   /** @var \Drupal\Core\Entity\EntityDisplayRepositoryInterface $entity_display_manager */
-  $entity_display_manager      = \Drupal::service('entity_display.repository');
+  $entity_display_manager = \Drupal::service('entity_display.repository');
 
   foreach ($entity_field_map as $entity_type_id => $field_map) {
     $entity_storage = $entity_type_manager->getStorage($entity_type_id);
@@ -51,7 +51,7 @@
       continue;
     }
 
-    $entity_type               = $entity_type_manager->getDefinition($entity_type_id);
+    $entity_type = $entity_type_manager->getDefinition($entity_type_id);
     $field_storage_definitions = $entity_field_manager->getFieldStorageDefinitions($entity_type_id);
     /** @var Drupal\Core\Entity\Sql\DefaultTableMapping $table_mapping */
     $table_mapping = $entity_storage->getTableMapping($field_storage_definitions);
@@ -62,7 +62,8 @@
 
       try {
         $table = $table_mapping->getFieldTableName($field_name);
-      } catch (SqlContentEntityStorageException $e) {
+      }
+      catch (SqlContentEntityStorageException $e) {
         // Custom storage? Broken site? No matter what, if there is no table
         // or column, there's little we can do.
         continue;
@@ -92,7 +93,7 @@
           continue;
         }
 
-        // Wipe it
+        // Truncate the table.
         $database->truncate($_table)->execute();
       }
 
@@ -103,12 +104,13 @@
 
       foreach (array_filter([$table, $revision_table]) as $_table) {
         if (!empty($existing_data[$_table])) {
-          // Build and execute the insert query
+          // Build and execute the insert query.
           $insert_query = $database->insert($_table);
-          $did_fields   = FALSE;
+          $did_fields = FALSE;
 
           foreach (array_keys($existing_data[$_table]) as $k) {
-            $existing_data_row = unserialize($existing_data[$_table][$k]["${field_name}_data"], ['allowed_class' => false]);
+            // @phpcs:ignore
+            $existing_data_row = unserialize($existing_data[$_table][$k]["${field_name}_data"], ['allowed_class' => FALSE]);
             $existing_data_row['title'] = $existing_data[$_table][$k]["${field_name}_title"];
             $existing_data_row['argument'] = $existing_data[$_table][$k]["${field_name}_argument"];
             $existing_data[$_table][$k]["${field_name}_data"] = serialize(array_filter($existing_data_row));
@@ -126,7 +128,7 @@
           $insert_query->execute();
         }
 
-        // Drop existing argument and title fields
+        // Drop existing argument and title fields.
         $database->schema()->dropField($_table, "${field_name}_argument");
         $database->schema()->dropField($_table, "${field_name}_title");
       }
@@ -135,26 +137,26 @@
       foreach ((array) $field_map[$field_name]['bundles'] as $bundle) {
         $bundle_fields = $entity_field_manager->getFieldDefinitions($entity_type_id, $bundle);
         /** @var \Drupal\core\Field\FieldConfigInterface $field_definition */
-        $field_definition             = $bundle_fields[$field_name];
-        $settings                     = $field_definition->getSettings();
+        $field_definition = $bundle_fields[$field_name];
+        $settings = $field_definition->getSettings();
         $keys = ['plugin_types', 'preselect_views'];
         foreach ($keys as $key) {
           if (array_key_exists($key, $settings)) {
-            // Remove not enabled options for a valid schema. Unchecked option was a integer 0.
-            // Allows are only strings.
+            // Remove not enabled options for a valid schema. Unchecked option
+            // was a integer 0. Allows are only strings.
             $settings[$key] = is_array($settings[$key]) ? array_filter($settings[$key]) : [];
           }
         }
 
         $settings['enabled_settings'] = [
           'argument' => 'argument',
-          'title'    => 'title',
+          'title' => 'title',
         ];
         $field_definition->setSettings($settings);
         $field_definition->save();
 
-        // Remove not enabled options for a valid schema. Unchecked option was a integer 0.
-        // Allows are only strings.
+        // Remove not enabled options for a valid schema. Unchecked option was
+        // an integer 0. Allows are only strings.
         $view_modes = $entity_display_manager->getViewModeOptionsByBundle($entity_type_id, $bundle);
         foreach (array_keys($view_modes) as $view_mode) {
           $viewDisplay = $entity_display_manager->getViewDisplay($entity_type_id, $bundle, $view_mode);
@@ -181,18 +183,18 @@
  *   The names of the new fields to be added.
  */
 function viewsreference_update_viewsreference_fields(array $columns_to_add = []) {
-  $field_type         = 'viewsreference';
-  $processed_fields   = [];
+  $field_type = 'viewsreference';
+  $processed_fields = [];
   $field_type_manager = \Drupal::service('plugin.manager.field.field_type');
-  $field_definition   = $field_type_manager->getDefinition($field_type);
-  $field_item_class   = $field_definition['class'];
+  $field_definition = $field_type_manager->getDefinition($field_type);
+  $field_item_class = $field_definition['class'];
 
-  $schema               = \Drupal::database()->schema();
-  $entity_type_manager  = \Drupal::entityTypeManager();
+  $schema = \Drupal::database()->schema();
+  $entity_type_manager = \Drupal::entityTypeManager();
   $entity_field_manager = \Drupal::service('entity_field.manager');
-  $entity_field_map     = $entity_field_manager->getFieldMapByFieldType($field_type);
+  $entity_field_map = $entity_field_manager->getFieldMapByFieldType($field_type);
   // The key-value collection for tracking installed storage schema.
-  $entity_storage_schema_sql    = \Drupal::keyValue('entity.storage_schema.sql');
+  $entity_storage_schema_sql = \Drupal::keyValue('entity.storage_schema.sql');
   $entity_definitions_installed = \Drupal::keyValue('entity.definitions.installed');
 
   foreach ($entity_field_map as $entity_type_id => $field_map) {
@@ -203,7 +205,7 @@
       continue;
     }
 
-    $entity_type               = $entity_type_manager->getDefinition($entity_type_id);
+    $entity_type = $entity_type_manager->getDefinition($entity_type_id);
     $field_storage_definitions = $entity_field_manager->getFieldStorageDefinitions($entity_type_id);
     /** @var Drupal\Core\Entity\Sql\DefaultTableMapping $table_mapping */
     $table_mapping = $entity_storage->getTableMapping($field_storage_definitions);
@@ -213,7 +215,8 @@
       $field_name = $field_storage_definition->getName();
       try {
         $table = $table_mapping->getFieldTableName($field_name);
-      } catch (SqlContentEntityStorageException $e) {
+      }
+      catch (SqlContentEntityStorageException $e) {
         // Custom storage? Broken site? No matter what, if there is no table
         // or column, there's little we can do.
         continue;
@@ -229,7 +232,7 @@
         }
       }
       // Load the installed field schema so that it can be updated.
-      $schema_key        = "$entity_type_id.field_schema_data.$field_name";
+      $schema_key = "$entity_type_id.field_schema_data.$field_name";
       $field_schema_data = $entity_storage_schema_sql->get($schema_key);
 
       $processed_fields[] = [$entity_type_id, $field_name];
@@ -239,7 +242,7 @@
         // Add `initial_from_field` to the new spec, as this will copy over
         // the entire data.
         $field_schema = $field_item_class::schema($field_storage_definition);
-        $spec         = $field_schema['columns'][$column_id];
+        $spec = $field_schema['columns'][$column_id];
 
         // Add the new column.
         $schema->addField($table, $column, $spec);
@@ -249,10 +252,10 @@
 
         // Add the new column to the installed field schema.
         if ($field_schema_data) {
-          $field_schema_data[$table]['fields'][$column]             = $field_schema['columns'][$column_id];
+          $field_schema_data[$table]['fields'][$column] = $field_schema['columns'][$column_id];
           $field_schema_data[$table]['fields'][$column]['not null'] = FALSE;
           if ($revision_table) {
-            $field_schema_data[$revision_table]['fields'][$column]             = $field_schema['columns'][$column_id];
+            $field_schema_data[$revision_table]['fields'][$column] = $field_schema['columns'][$column_id];
             $field_schema_data[$revision_table]['fields'][$column]['not null'] = FALSE;
           }
         }