How do I programmatically add fields to a custom entity bundle?

Question

I created a custom Entity, using the following code in the CustomEntity.php file.

public static function baseFieldDefinitions(EntityTypeInterface $entity_type) {
  $fields = parent::baseFieldDefinitions($entity_type);

  $fields['name'] = BaseFieldDefinition::create('string')
    ->setLabel(t('Name'))
    ->setDescription(t('Name'))
    ->setSettings([
      'max_length' => 50,
      'text_processing' => 0,
    ])
    ->setDefaultValue('')
    ->setDisplayOptions('view', [
      'label' => 'above',
      'type' => 'string',
      'weight' => -4,
    ])
    ->setDisplayOptions('form', [
      'type' => 'string_textfield',
      'weight' => -4,
    ])
    ->setDisplayConfigurable('form', TRUE)
    ->setDisplayConfigurable('view', TRUE);

  return $fields;
}

We can add fields for the entity and all bundles will automatically inherit them.

I set a bundle in the myModule/config/install/myModule.customEntity.bundleA.yml file.

uuid: db129d12-849a-4e68-bb56-d787b4b0cf42
langcode: en
status: true
dependencies: {  }
id: bundleA
label: bundleA

How can I programmatically add fields to that bundle?

Answer 1

An entity class can implement FieldableEntityInterface::bundleFieldDefinitions() to add fields to a bundle, but as that documentation page says, the recommended approach is another one.

This function can return definitions both for bundle fields (fields that are not defined in $base_field_definitions, and therefore might not exist on some bundles) as well as bundle-specific overrides of base fields (fields that are defined in $base_field_definitions, and therefore exist for all bundles). However, bundle-specific base field overrides can also be provided by 'base_field_override' configuration entities, and that is the recommended approach except in cases where an entity type needs to provide a bundle-specific base field override that is decoupled from configuration.

As for decoupling the bundle fields from the configuration, the same page says:

Note that for most entity types, the bundles themselves are derived from configuration (e.g., 'node' bundles are managed via 'node_type' configuration entities), so decoupling bundle-specific base field overrides from configuration only makes sense for entity types that also decouple their bundles from configuration.

Finalize API for creating, overriding, and altering code-defined bundle fields could change how bundle fields are created. That issue isn't yet marked as fixed, and it has been opened 8 years ago.