`label` not defined in `entity keys` in `taxonomy_entity_info`

[bennybobw]

Label is not defined in taxonomy_entity_info entity keys

I looked at the Drupal 7 version of taxonomy_entity_info and it defines label under
I opened an issue over in the 'Title' module where it wasn't checking whether that array key existed and @argiepiano suggested opening a core issue

Current code

in core/modules/taxonomy/taxonomy.module

  $entity_info = array(
    'taxonomy_term' => array(
      'label' => t('Taxonomy term'),
      'bundle label' => t('Vocabulary'),
      'entity class' => 'TaxonomyTerm',
      'controller class' => 'TaxonomyTermController',
      'base table' => 'taxonomy_term_data',
      'token type' => 'term',
      'fieldable' => TRUE,
      'redirect support' => TRUE,
      'entity keys' => array(
        'id' => 'tid',
        'bundle' => 'vocabulary',
      ),

Suggested Code

  $entity_info = array(
    'taxonomy_term' => array(
      'label' => t('Taxonomy term'),
      'bundle label' => t('Vocabulary'),
      'entity class' => 'TaxonomyTerm',
      'controller class' => 'TaxonomyTermController',
      'base table' => 'taxonomy_term_data',
      'token type' => 'term',
      'fieldable' => TRUE,
      'redirect support' => TRUE,
      'entity keys' => array(
        'id' => 'tid',
        'bundle' => 'vocabulary',
        'label' => 'name'
      ),

I don't fully understand what label is notating in this case, so I'll wait for someone else to chime in before creating a pull request.

[bennybobw]

Hm. This is really weird because I swear @avpaderno commented on this ticket. I want to respond to their comment:

I thought that Backdrop did not need the label => 'name' line because the class for the taxonomy term entity (TaxonomyTerm) has the label() method, similarly to what happen with the User entity. (See User and user_entity_info().)

If that was the case, user_entity_info() should neither have a 'id' => 'uid' line, since User::id() exists.

There is a lot of code in this title module that does things like this:

  $entity_info = entity_get_info($type);
  $legacy_field = $entity_info['entity keys']['label'];
  $info = $entity_info['field replacement'][$legacy_field];

The User and TaxonomyTerm label methods aren't static, so since we don't have an actual instantiated entity I think we still need these?

Someone let me know if I'm wrong!

[herbdool]

This is when it was added to Drupal 7 https://git.drupalcode.org/project/drupal/-/commit/b06d19e34957bd3e719dfcff9e6d180ea95330e5. I'm not against adding them back if they don't interfere with anything. But we'll have to look at the reasons for why they were removed. And let @quicksketch chime in. Here's the issue where they were removed: #164

There have been other calls here and there to have some way of getting at entity type info without instantiating an entity. Doesn't happen often, but Title appears to be one of those times. That might be the only remaining use case.

Note: all core entities do not have label under entity keys.

[argiepiano]

The ['entity keys']['label'] key was used in Drupal to tell core the name of the entity's table column that held the label for the entity. For example, for node, the column that holds the label for each node is title - you can see that column in the node table. Additionally, this key also told core the name of the entity property used as the label of the entity (in D7 and Backdrop, the this entity property matches the name of the table column used to store the entity label).

This entity "metadata" was used in many places in Drupal, 7, for example, by the function entity_label(). This function was completely revamped in Backdrop.

So, in Backdrop, instead of providing the name of the column (or property) holding the label of the entity as metadata in order to get the entity title, we rely on the entity class itself to do this (e.g. Node::label()). If you look at Backdrop's entity_label() you'll see that the function has been greatly simplified - it just invokes $entity->label(), a method that is required in all entity classes in Backdrop.

Of course, this type of changes will always create some issues. For example, what you encountered in the contrib title. Also entity_plus relies on $info['entity keys']['label'].

So, in my opinion, rather than adding 'label' back, we should modify contrib to make the proper call to $entity->label() to obtain the label.

(edited to fix typos!)

[avpaderno]

The User and TaxonomyTerm label methods aren't static, so since we don't have an actual instantiated entity I think we still need these?

Without an actual instantiated entity, it is not possible to access any object properties too. Node::label() returns the node title, not a value that is valid for all nodes, like Node.

[avpaderno]

I removed my comment because I felt it did not add much to this issue.

Since Backdrop entities are implemented as class instances, not stdClass() instances, for each property there is a method which returns its value. It is not necessary to know the name of the property because the name of the method returning its value is the same for all the entity types (::label(), in this case).

The entity properties have been left public, probably for backward compatibility with Drupal 7 code. If this were the case, probably the 'entity keys' array should be kept for the same reason.

[bennybobw]

I'm working on fixing up the title module for nodes as well and it has the same problem.

I can add code to hook_entity_info_alter to achieve what I need. I guess there are not too many

One question I have is around calling ::label() for instantiated entities -- is there a way for other modules to override these methods?

[argiepiano]

I can add code to hook_entity_info_alter to achieve what I need. I guess there are not too many

That's a good way to approach this.

is there a way for other modules to override these methods?

Yes, but with a caveat. PHP lets you easily extend entity classes like Node. You can also use hook_entity_info_alter() to provide a different 'entity class' key. BUT...

Unfortunately, there are still several places in Backdrop core that hard-code things like $node = new Node();, which effectively "kills" the ability to use a different entity class for nodes (same for File, User, etc).

In fact I created an issue a few years ago to fix those hard-coded places and replace them with the entity constructor entity_create(). But it gained no traction. Perhaps if you post there it will be revived?

#6075

[bennybobw]

I'm closing this request because we're actually addressing it over in #6877 after some discussion in the Backdrop core developer meeting last week.