Consider moving some of the module logic into services or OO code so that it can be easily tested and other modules can make use of it

Rerolled. It seems like most of this was committed in #3104318: Create tests and a config schema for taxonomy_entity_index.settings → .

The last submitted patch, 5: taxonomy_entity_index-n3109723-5.patch, failed testing. View results →
- codesniffer_fixes.patch Interdiff of automated coding standards fixes only.

taxonomy_entity_index_entity_update() needs to be replaced next.

I updated the issue summary.

And then another for the db operations.

Which ones specifically?

The test fails because the static cache in the FieldInformation service is not invalidated when the field is added.

Is this the problem?

Nope, #9 is not the correct approach.

Great work 🙌

I'd be keen to also add something to extract TID values from an entity too. Been running custom code for that on a few projects.

1. +++ b/src/FieldInformation.php
   @@ -0,0 +1,91 @@
   +    $cache_id = 'entity-taxonomy-fields_' . $entity_type_id;
   

   do we need the entity-taxonomy-fields_ prefix? we're only storing one thing in the cache and its per entity-type

2. +++ b/src/FieldInformation.php
   @@ -0,0 +1,91 @@
   +          if ($field_definition->getSetting('target_type') === 'taxonomy_term') {
   

   We can read this from the field storage definition as the target-type is a storage level setting, will likely mean we can avoid the ::getFieldDefinitions call inside the two inner for each loops.

   \Drupal\Core\Entity\EntityFieldManager::getFieldStorageDefinitions can be called outside both loops, and then if a $field_name key exits, we can call

   ::getSetting</code on that.
   
   Should be dramatically more performant.
   
   I realise we're just moving existing code, but we may as well speed it up while we're at it.
   </li>
   
   <li>
   <code>
   +++ b/taxonomy_entity_index.module
   @@ -157,44 +157,14 @@ function taxonomy_entity_index_entity_update(EntityInterface $entity) {
   +  @trigger_error('taxonomy_entity_index_get_taxonomy_field_names() is deprecated in taxonomy_entity_index:8.x-1.13. Use the \Drupal\taxonomy_entity_index\FieldInformation service instead.', E_USER_DEPRECATED);
   

   this will be 8.x-1.15 now (at least)

Oh, right, I wrote the first version of the patch and said the same thing 🤦 three year ago 😂

do we need the entity-taxonomy-fields_ prefix? we're only storing one thing in the cache and its per entity-type

The module includes optional support for per-field index instead of per-entity-type. I have not dug into the logic behind it yet, but I suspect that's part of it.