Change node type field to an entity reference

Sure we want this? Because getting all article nids was (so) straight. $nids = db_query("SELECT nid FROM {node} WHERE type = :type", array(':type' => 'article'))->fetchCol() :(

In the new world order, that's what EntityFieldQuery is for:
Something like

$nids = Drupal::entityQuery('node')->condition('type', $type)->execute();

should do the trick. In D8 you will almost never write a direct query anyway, unless you're writing a storage backend.

Edit: Apparently, EFQ -> EQ

This means that type will go out from {node} (plus {node_field_data}, {node_field_revision}) and will be stored, as body, in his own table?

More:

1. The field widget should be hidden (locked) by default in node forms?
2. Every new node bundle will automatically get an instance of Entity Reference field?

I hope what Xano meant was to use the entity reference field that came with the new Entity API (Drupal\Core\Entity\Plugin\DataType\EntityReferenceItem) not the configurable field provided by the Entity reference module (Drupal\field\Plugin\Type\FieldType\ConfigEntityReferenceItemBase), which means that it will still be stored in the base tables of the node entity.

Ok, ok, that sounds good. I was tempted to take this task but I got no other similar example in core and, as I'm not 100% familiar with this, I don't know exactly were to start :)

I think this is what we want here... or I'm missing something.

With this patch, the node type entity can be reached in this way:

$node->get('type')->entity;

$node->getNodeType();

Yep, that's exactly what we need :) This probably needs to be extended to all content entity types, and I would prefer to do it in a single issue/patch since it's such a small change.

From IRC:

Xano: claudiu_cristea: Then I'd add a setter to the interface as well

It seems to me a read-only property but let's debate this. Opinions?

Unfortunately it breaks Condition tests. What I found is that validate fails in \Drupal\Core\Plugin\ContextAwarePluginBase::setContextValue() . It seems that, somewhere, the validation still tries to check $node->type[0]['target_id'] for node type value. It should check $node->type.

EDIT: And this seems something changed by the fact that type is now entity_reference_field.

Think somebody else has to take this.

This has been committed already in #2112239: Convert base field and property definitions, yay!