Empty field for Drupal core Layout builder (layout_builder)

Unfortunately this does not seem to work when Allow each content item to have its layout customized. is enabled and a per-entity layout wants to display a field with empty fields config that is not available in the default layout builder config for the an entity view mode.

Steps to reproduce:

• Create a node type and enable layout builder for its Full display
• Leave the Full display completely empty (in layout builder as well as in normal field UI)
• Enable Allow each content item to have its layout customized. for Full view mode
• Create a node of that type
• Use the Layout tab to add fields to the layout and add a field that is empty, configure its empty field settings and save the per-node layout
• Check the output -> the field is not outputted with the selected empty field behavior

If you add that field to the default layout for the Full view mode at admin/structure/types/manage/NODE_TYPE/display/full/layout, accessing node/ID throws the following error:

TypeError: array_merge(): Argument #1 must be of type array, null given in array_merge() (line 215 of modules/contrib/empty_fields/empty_fields.module).

Accessing node/ID/layout displays everything the correct way - with empty field fallback and without any errors.

So, I guess there is still some work to do :(

both cases from comment #30 should be added to test

Roll in the similar one-liner change from 3192991 🐛 Contrib module classes are overwritten Needs review since it was closed in favor of this issue.

Undoing #33. Misread the other issue.

Improved patch from #24 and used \Drupal\layout_builder\LayoutBuilderEvents::SECTION_COMPONENT_BUILD_RENDER_ARRAY instead.
This way we have build and all correct third party settings depending on entity, if it has overrides.
Also noticed test fail on D9.5, so made changes so it passes both cases. I checked locally and visually nothing changed, html output for field is the same, probably test engine method that were retrieving html changed.
Added functional javascript test as well to make sure empty fields working for default and custom layouts on test node type.

1. +++ b/empty_fields.services.yml
   @@ -2,3 +2,9 @@ services:
   +  empty_fields.event_subscriber:
   +    class: Drupal\empty_fields\EventSubscriber\EmptyFieldsSubscriber
   +    arguments: ['@plugin.manager.empty_fields']
   +    tags:
   +      - { name: event_subscriber }
   

   is needs change but for 10.2+ https://www.drupal.org/node/3357408 →

   let's keep it as is

2. +++ b/src/EventSubscriber/EmptyFieldsSubscriber.php
   @@ -0,0 +1,109 @@
   +  protected $manager;
   ...
   +  public function __construct(EmptyFieldsPluginManager $empty_fields_plugin_manager) {
   +    $this->manager = $empty_fields_plugin_manager;
   

   it should use constructor promotion

please convert patch to MR

Hi @andypost
thank you for your comments, MR created

Same as #38 just in patch file format for our composer based builds to rely on.