[regression] EntityStorageException when reverting layout to defaults after entity field values

[update] Thanks quietone, my apologies I was unaware of the AI disclosure policy. AI was used for this issue summary, but I verified it all, and it's suggested fix is currently in use on my site. [/update]

Problem/Motivation

The fix committed in #3035992: Stale values can be displayed by the Layout Builder UI but are saved correctly introduced a regression in LayoutOverrideFieldHelper::updateTempstoreEntityContext(). When a node is edited via the normal edit form while a Layout Builder tempstore exists, the method replaces the stored entity context with the post-save entity object. This post-save entity carries a new revision ID (because the node edit created a new revision), but the OverridesSectionStorage was originally loaded against the previous revision.

When the user subsequently clicks "Revert to defaults," RevertOverridesForm::submitForm() calls $this->sectionStorage->removeAllSections()->save(), which internally calls $this->getEntity()->save(). SqlContentEntityStorage detects the revision ID mismatch between the entity's claimed revision and the loaded revision, and throws:

Drupal\Core\Entity\EntityStorageException: Update existing 'node' entity
revision while changing the revision ID is not supported.

Environment: Drupal 11.x-dev. Also reproduced on Drupal 10.6.7 with the #3035992 patch backported.

Steps to reproduce

1. Enable Layout Builder on a content type with "Allow each content item to have its layout customized" checked (e.g., at /admin/structure/types/manage/page/display/default)
2. Create a node of that type with body text "original" and save it
3. Open the node's Layout Builder page at /node/1/layout — this creates a tempstore entry via the PrepareLayout event subscriber
4. Navigate away from Layout Builder without clicking "Save layout" or "Discard changes" (e.g., click the "View" tab or use the browser back button)
5. Edit the node at /node/1/edit, change the body text to "updated", and save
6. Open /node/1/layout again — the updated body text "updated" is correctly displayed (the #3035992 fix is working)
7. Click "Revert to defaults" and confirm

Expected behavior: The layout reverts to the default display and redirects to the node view showing the current field values.

What happened instead: An uncaught EntityStorageException is thrown:

Drupal\Core\Entity\EntityStorageException: Update existing 'node' entity
revision while changing the revision ID is not supported.
in Drupal\Core\Entity\Sql\SqlContentEntityStorage->save()

Full stack trace:

SqlContentEntityStorage->save() (line 815)
EntityBase->save() (line 370)
OverridesSectionStorage->save() (line 331)
RevertOverridesForm->submitForm()
FormSubmitter->executeSubmitHandlers()
FormSubmitter->doSubmitForm()
FormBuilder->processForm()
FormBuilder->buildForm()
FormController->getContentResult()

Proposed resolution

In LayoutOverrideFieldHelper::updateTempstoreEntityContext(), instead of assigning the post-save entity directly, reload the entity fresh from storage using EntityStorageInterface::load(). This returns the current default revision with all internal state (revision ID, original values, loaded revision tracking) fully consistent with the database. Then copy only the layout field from the tempstore to preserve in-progress layout changes.

Replace:

$updated_entity = $entity;
$updated_entity->{OverridesSectionStorage::FIELD_NAME} = $stored_entity->{OverridesSectionStorage::FIELD_NAME};

With:

$entity_storage = \Drupal::entityTypeManager()->getStorage($entity->getEntityTypeId());
$updated_entity = $entity_storage->load($entity->id());
$updated_entity->{OverridesSectionStorage::FIELD_NAME} = $stored_entity->{OverridesSectionStorage::FIELD_NAME};