Deleting a paragraph type can delete a field holding multiple paragraphs, not just that one reference

Yeah, it seems we enforced dependencies...
Since the deleted field is indicated, i'm not marking it critical. But i can see that this can lead to unexpected data loss and i doubt everyone really ready those pieces before confirming...

Instead we could decouple that dependency and simply remove the reference to the deleted paragraph type in the field configuration.

Still asking Berdir if this is well aligned with how Core decided to handle such a situation.

#2468045: When deleting a content type field, users do not realize the related View also is deleted

paragraph can't do anything about this, it's not our field type. If anything, then this needs to be fixed in ERR so it updates the field. but that's always hard, if you remove the last allowed value, then you implicitly allow all, so what then? Maybe only delete if there are still some left.

I don't think deleting a content type should ever delete a reference field just because it can point to that type. With core ER fields the field is updated, and when the last target entity type gets removed the system logs a critical message stating that the field is no longer in a valid state. I have essentially copied that code and changed the message to be less alarming since it is a valid state for ERR.

Makes sense to me to simply follow the ER case.

Is there some similar test coverage we can steal over there too? That's quite some code complexity that is hit a lot.

can't we just let it inherit from the parent? I thought we have the same settings structure?

It would probably work if it inherited from the parent however the message and code comments would contain incorrect information, and the logger would be posting for entity_reference instead of entity_reference_revisions:

              // In case we deleted the only target bundle allowed by the field
              // we have to log a critical message because the field will not
              // function correctly anymore.
              if ($handler_settings['target_bundles'] === []) {
                \Drupal::logger('entity_reference')->critical('The %target_bundle bundle (entity type: %target_entity_type) was deleted. As a result, the %field_name entity reference field (entity_type: %entity_type, bundle: %bundle) no longer has any valid bundle it can reference. The field is not working correctly anymore and has to be adjusted.', [

I didn't find anything in entity reference that checks for unnecessary field and data deletion when removing a target entity bundle, but there is some tests about dealing with multiple bundles including deleting one in EntityReferenceAdminTest so it looks like the equivalent class in ERR is where this would go.

#9 should work once #2817871: Tests are broken on head is fixed.

Rerolling patch. :).

We have similar problems with a custom entity type with bundles, where deleting one entity type will delete the entity-revision-reference field from a content-type. Applying the patch seem to fix it on our end.

Again duplicated by #2925591: Deleting a nested paragraph type also deletes host paragraph field from Paragraphs.

Somehow this issue got lost..

Committed, looks good. :-)

Lost data due to this issue 2 days before project deadline while deleting an unused paragraph. The reference field was set to "exclude" a couple paragraphs, therefore include all others. No content was entered on the site using the paragraph I deleted. The reference field was a "components" field that was setup to reference 6 or 7 different paragraphs. Rather than mark the paragraphs I wanted, I excluded the ones I didn't want. One of the paragraphs excluded was the one I deleted. The paragraph was excluded, meaning it was not displayed on any of the content types using the reference field, so absolutely no content data was entered using that paragraph. Deleting it caused my "components" field to be deleted. This resulted in the loss of all page data as the 'components' field was being used as a 'page-builder' for constructing page content. So all page content is lost. Paragraphs 1.2, Drupal 8.4.3