Add SubEntityInterface, getParent()/hasParent() methods, and parent_entity_type/parent_id base fields to SubEntityBase
>>> [!note] Migrated issue
<!-- Drupal.org comment -->
<!-- Migrated from issue #3593856. -->
Reported by: [macsim](https://www.drupal.org/user/2664025)
Related to !20
>>>
<h3>Problem/Motivation</h3>
<p><code>SubEntityBase</code> is almost entirely empty. It extends <code>ContentEntityBase</code> but adds no helper methods for module developers who implement a subentity type.</p>
<p>Two common needs are completely unaddressed:</p>
<ol>
<li>Retrieving the parent entity from a subentity instance.</li>
<li>Checking whether a given entity is a subentity at all, without coupling to the concrete class.</li>
</ol>
<p>Currently, the only way to find the parent is through <code>EntityParentHandler::getStorageByEntityType()</code>, which issues database queries for every subentity row — an O(n) query problem for any listing.</p>
<h3>Proposed resolution</h3>
<h4>1. Add parent_entity_type and parent_id base fields to SubEntityBase</h4>
<p>Store the parent reference directly on the subentity so it is always available without scanning referencing fields:</p>
<pre>public static function baseFieldDefinitions(EntityTypeInterface $entity_type): array {<br> $fields = parent::baseFieldDefinitions($entity_type);<br><br> $fields['parent_entity_type'] = BaseFieldDefinition::create('string')<br> ->setLabel(new TranslatableMarkup('Parent entity type'))<br> ->setRequired(FALSE)<br> ->setSetting('max_length', 128)<br> ->setReadOnly(TRUE);<br><br> $fields['parent_id'] = BaseFieldDefinition::create('integer')<br> ->setLabel(new TranslatableMarkup('Parent entity ID'))<br> ->setRequired(FALSE)<br> ->setReadOnly(TRUE);<br><br> return $fields;<br>}</pre><p>These fields are populated automatically when the subentity is saved through <code>ReferencedEntityForm</code> or via a <code>hook_entity_presave</code> on the parent.</p>
<h4>2. Add SubEntityInterface with getParent() and hasParent()</h4>
<p>Define a proper interface so consumer modules do not need to couple to the concrete base class:</p>
<pre>interface SubEntityInterface extends ContentEntityInterface {<br><br> /**<br> * Returns the parent entity, or NULL if none is found.<br> */<br> public function getParent(): ?EntityInterface;<br><br> /**<br> * Returns TRUE if a parent entity can be resolved.<br> */<br> public function hasParent(): bool;<br><br>}</pre><p>The implementation in <code>SubEntityBase</code> reads directly from the new base fields:</p>
<pre>public function getParent(): ?EntityInterface {<br> $type = $this->get('parent_entity_type')->value;<br> $id = $this->get('parent_id')->value;<br> if (!$type || !$id) {<br> return NULL;<br> }<br> return $this->entityTypeManager()->getStorage($type)->load($id);<br>}<br><br>public function hasParent(): bool {<br> return $this->getParent() !== NULL;<br>}</pre><p>Having an interface also replaces fragile <code>is_subclass_of($entity, SubEntityBase::class)</code> checks with the standard <code>$entity instanceof SubEntityInterface</code> pattern.</p>
<h3>Remaining tasks</h3>
<ul>
<li>Add <code>parent_entity_type</code> and <code>parent_id</code> base fields in <code>SubEntityBase::baseFieldDefinitions()</code>.</li>
<li>Add a <code>hook_update_N</code> in <code>subentity.install</code> to install the new field storage definitions on sites where the module is already installed, using <code>entityDefinitionUpdateManager()->installFieldStorageDefinition()</code> for each subentity type.</li>
<li>Add a <code>hook_post_update</code> in <code>subentity.post_update.php</code> to backfill <code>parent_entity_type</code> and <code>parent_id</code> on all existing subentity records by delegating to <code>EntityParentHandler</code> — this hook runs after all <code>hook_update_N</code> have completed, making it the right place for data migrations that depend on the schema being up to date.</li>
<li>Populate these fields in <code>ReferencedEntityForm</code> on save.</li>
<li>Define <code>SubEntityInterface</code> in a new <code>src/SubEntityInterface.php</code> file.</li>
<li>Implement the interface and the two methods in <code>SubEntityBase</code>.</li>
<li>Update <code>ReferencedEntityListBuilder::buildRow()</code> to read <code>parent_entity_type</code> and <code>parent_id</code> directly instead of calling <code>EntityParentHandler</code> per row.</li>
<li>Update the Drush generator template to declare <code>implements SubEntityInterface</code> on the generated entity class.</li>
<li>Add a kernel test covering <code>getParent()</code> and <code>hasParent()</code>.</li>
</ul>
<h3>Original report</h3>
<p>Identified while reviewing the module architecture. The lack of stored parent references forces repeated database scans and makes type-checking fragile.</p>
issue
GitLab AI Context
Project: project/subentity
Instance: https://git.drupalcode.org
Before proposing or making any changes, READ each of these files and FOLLOW their guidance:
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Repository: https://git.drupalcode.org/project/subentity
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