Experimental asymmetrical content translation with Paragraphs breaks concurrent drafts

This has been identified in Paragraphs in the related issue. There will be actions to take in ERR, Paragraphs and likely Core as well to fix this.

You start best with reviewing the test coverage in the related issue and maybe improve it if we will need to test more. Fixing is going to be hard and will likely first address the case without asymmetric translation.

Ok, here we go.

I did *not* test this yet with paragraphs, this just contains an API test. So please make sure that this works when using paragraphs with the async translation widget patches.

If you still experience issues, have a close look at how many entities/translations you have and if the content of the other translations is changing when you cange a certain translation. You can also look at the translations that are affected by a given revision by looking at the /revisions page of each translations, you should not be seeing any revisions from other translations there.

+++ b/src/Plugin/Field/FieldType/EntityReferenceRevisionsItem.php
@@ -254,24 +255,35 @@ class EntityReferenceRevisionsItem extends EntityReferenceItem implements Option
+      // The item is considered to be affected if the field is either
+      // untranslatable or there are translation changes. This prevents
+      // that new revisions are created on translatable fields for all
+      // translations every time the entity is saved.
+      $is_affected = !$this->getFieldDefinition()->isTranslatable() || ($host instanceof TranslatableRevisionableInterface && $host->hasTranslationChanges());

This is the crucial part.. only creating a new revision if the current host translation has translation changes.

Performance is a concern here, since calculating that multiple times in a request is quite slow. But the problem is that \Drupal\Core\Entity\ContentEntityBase::isRevisionTranslationAffected() is at that point not yet re-calculated that only happens after the preSave() hook/field plugin method calls.

Cleaned up a weird test that was no failing which was due to some static cache side effects, not sure how it did *not* fail before. Also improved comments on some assertions there that were very confusing.

Test wasn't properly fixed yet, was actually not only the static cache, using the old object meant it didn't have parent fields yet and was saving again in postSave().

Just a couple of things I noticed while looking at this:

1. +++ b/src/Plugin/Field/FieldType/EntityReferenceRevisionsItem.php
   @@ -254,24 +255,35 @@ class EntityReferenceRevisionsItem extends EntityReferenceItem implements Option
   +      // The item is considered to be affected if the field is either
   +      // untranslatable or there are translation changes. This prevents
   +      // that new revisions are created on translatable fields for all
   +      // translations every time the entity is saved.
   

   I think the comments should say that this prevents all revision translation from being marked as affected, because we do get a new revision translation value for each field regardless.

   Also, does not wrap at 80 chars :)

2. +++ b/src/Plugin/Field/FieldType/EntityReferenceRevisionsItem.php
   @@ -254,24 +255,35 @@ class EntityReferenceRevisionsItem extends EntityReferenceItem implements Option
   +      $is_affected = !$this->getFieldDefinition()->isTranslatable() || ($host instanceof TranslatableRevisionableInterface && $host->hasTranslationChanges());
   

   TranslatableInterface should be enough here, I guess we already assume we are dealing with a revisionable entity type :)

Will commit after quick update and passes. :-)

Missed that review.

1. Improved the comment.

2. I used (and kept) this interface because below, we also call things like $host->isNewRevision() and then PHPStorm complains that those don't exist on TranslatableInterface, by using that other interface, I have all methods covered that I'm calling on $host.

Passed, committed. Awesome. :-)

These changes introduce the new problem: #2984027: Incorrect manipulation of default revision flag