Limit source entities in settings to ones that have fields

Here's the patch

+++ b/src/Form/EntityUsageSettingsForm.php
@@ -113,8 +114,13 @@ class EntityUsageSettingsForm extends ConfigFormBase {
+      // If the entity type doesn't have fields it can't be a source, e.g. views
+      if (method_exists($entity_type->getOriginalClass(), 'getFields')) {
+        $source_options[$entity_type->id()] = $entity_type->getLabel();

I think we should be checking FieldableEntityInterface so something like:

      if ($entity_type->entityClassImplements(FieldableEntityInterface::class)) {
        $source_options[$entity_type->id()] = $entity_type->getLabel();
      }

You will need to add a use statement too.

FWIW I think this is a bug.

I think theoretically you could implement any entity tracking plugin that does not use fields BUT the entity track plugin definition has field_types so it is going to be quite hard.

But this potentially would break such a use-case. Maybe the way around this is to look at all the entity track plugins and check to see if the extend from \Drupal\entity_usage\EntityUsageTrackBase - if they all do then there we should not include non-fiedldable types. This would improve the UI for 99.5% of users.

Working on it.

Checking using FieldableEntityInterface seems to filter out the entity types without any fields from the source entities list. Created the MR !116 according to it.
I have not tried using the EntityUsageTrackBase as I am not clear of the idea of how to use it to check for entities without fields.

I've fixed the tests and implemented my suggestion about checking the plugins. Ideally we'd have a more concrete way to deal with this. Also we need to think about upgrade paths and the like.

So what I think we should do here is an a new value to the tracking plugin config - 'source_entity_class' and then trigger a deprecation when a plugin does not implement it. That way we can limit the source entity type list using this information.

I agree it's a lot of code but definitely the most flexible fix. Thanks for writing it!
I have fixed a minor typo on commit.

Automatically closed - issue fixed for 2 weeks with no activity.

The update function was causing issues when we were updating to Drupal 11 and using the group module, which gets upgraded from v2->v3 in this process. Adding the fix here in case it helps anybody. Thx!
> [error] Update failed: entity_usage_post_update_remove_unsupported_source_entity_types

https://www.drupal.org/project/group/issues/3512099 🌱 The "group_content" entity type does not exist + content_lock module Active