Selecting the 'views' selection handler on an entity_reference field causes a fatal error

The patch and test looks great, just one tiny nitpick:

+++ b/core/modules/entity_reference/src/Tests/EntityReferenceAdminTest.php
@@ -28,7 +28,7 @@ class EntityReferenceAdminTest extends WebTestBase {
+  public static $modules = array('node', 'field_ui', 'entity_reference', 'path', 'taxonomy', 'block', 'views', 'views_ui');

We don't need to enable the views_ui module :)

+++ b/core/modules/views/src/Plugin/EntityReferenceSelection/ViewsSelection.php
@@ -120,12 +120,18 @@ public function buildConfigurationForm(array $form, FormStateInterface $form_sta
+      $account = \Drupal::currentUser();
+      if ($account->hasPermission('administer views') && \Drupal::moduleHandler()->moduleExists('views_ui')) {

If we're going down this path, the current_user and module_handler services can be injected in the plugin.

Perfect!

Why does #element_validate have to be static? I.e can't we do

$form['view']['#element_validate'] = array(array($this, 'settingsFormValidate'));

By declaring element validate (also process, etc.) handlers as a static methods we skip a lot of form object serialization. Field API does this consistently all over the place :)

Huh http://3v4l.org/S0onn?

Basically I don't get the argument in #25 - using $this will not save any form serialisation and if the form is serialised the object detection in serialisation might well end up being more memory efficient that storing the classname.

When you start adding objects (e.g. entities, services) to $d, all of them will need to go through the serialization process, while the simple array(array('\some\class\name', 'someMethod')) will not.

Yeah but this is $this

I don't understand #29.

re #29 - there is no saving when doing get_called_class($this) because $this is what is being serialised.

It's not the $this that is serialized. It's $form, containing references to $this. And if we make that static, then we can avoid that being serialized. As @amateescu said, field api widgets use that pattern a lot.

Being able to do this is one of the main reasons I introduced support for '::methodName' , but that only works in the actual form objects.

See http://3v4l.org/ALTTj

I agree that we should serialize as less as possible to avoid deep-object-references.

Ok get_called_class it is - not going to fight - but it makes code less testable and dependencies less obvious.

I agree that we should serialize as less as possible to avoid deep-object-references.

We have object serialization going on all over the place.

Looks like Alex has been all over this one.

This issue addresses a major bug and is allowed per https://www.drupal.org/core/beta-changes. Committed 9dfa950 and pushed to 8.0.x. Thanks!