Handle update and delete of Block `Component`s, plus react to dependency removal

👍

This should add \Drupal\Tests\experience_builder\Kernel\Plugin\ExperienceBuilder\ComponentSource\BlockComponentTest and test Delete block component config entities once the plugin (or derivative) no longer exists. — by for example deleting a Menu config entity, which will result in \Drupal\system\Plugin\Derivative\SystemMenuBlock deriving one fewer block.

I bet there will be config dependency-related challenges 😇 In fact … I see that the necessary config dependencies are missing currently. For example the experience_builder.component.block.system_menu_block.admin XB Component:

uuid: 784eab71-dbfa-49da-b932-dc703a5de2f8
langcode: en
status: true
dependencies: {  }
label: 'Administration block'
id: block.system_menu_block.admin
provider: system
source: block
category: Menus
settings:
  plugin_id: 'system_menu_block:admin'
  default_settings:
    id: 'system_menu_block:admin'
    label: Administration
    label_display: ''
    provider: system
    level: 1
    depth: 0
    expand_all_items: true

😱

That

dependencies: {  }

should be

dependencies:
  config:
    - system.menu.admin

That is an oversight/bug when Block support was first added in #3475584: Add support for Blocks as Components.

Yay for #3501290: Introduce unit test coverage for both ComponentSource plugins (Block + SDC) providing the appropriate place for this new test coverage!

I found a few problems in the MR, but I'm wondering if that's my brain still readjusting from the weekend? 🙈

Right. 🤔

What I'd like to see in the test coverage is — somehow — verifying that there's a confirmation dialog when humans try to delete a menu, which would then inform the user that they're making this component obsolete.

But we explicitly wanted to add the dependencies here, so what should we do? Prevent the menu from being deleted, or only have a soft dependency on the menu existing?

I don't think we need to prevent it. But we need to ensure that we do not cascade it down: if a ContentTemplate depends on a Component that depends on a Menu, the current code is basically saying that Component and ContentTemplate will disappear on you! That's bad 😅

I think we should implement \Drupal\Core\Config\Entity\ConfigEntityInterface::onDependencyRemoval(), to prevent that? 😇

Same exact challenge appeared over at #3519168-10: Handle components provided by ComponentSources EXPLICITLY disappearing — enables deleting JS components that are in use overnight! 😅

IDK about all of XB's config entities — perhaps only Component::onDependencyRemoval() is sufficient to start. Because … how do we remove a component instance in a Pattern, PageRegion or ContentTemplate that itself contains other component instances?! 😅

I guess we could do it automatically if the component instance is provided by a ComponentSource that does not implement \Drupal\experience_builder\ComponentSource\ComponentSourceWithSlotsInterface?

FYI In #3519168: Handle components provided by ComponentSources EXPLICITLY disappearing — enables deleting JS components that are in use I've added a fallback plugin that can step in and continue to render children when a JS component is removed if any instance exist.

@longwave: I think there's still things here that make sense to land independently of #3519168: Handle components provided by ComponentSources EXPLICITLY disappearing — enables deleting JS components that are in use?

@f.mazeikis fyi there's some overlap with #3519168: Handle components provided by ComponentSources EXPLICITLY disappearing — enables deleting JS components that are in use here that it would be good to be across, would appreciate your review there too - thanks!

@larowlan Yes, there's not just an overlap - this issue is pretty much blocked on #3519168.

#3519168: Handle components provided by ComponentSources EXPLICITLY disappearing — enables deleting JS components that are in use is in!

Responded to feedback, added additional test cases.

Very nice to see this solved so elegantly now! 😊

Retitling given the scope changed post-#3519168: Handle components provided by ComponentSources EXPLICITLY disappearing — enables deleting JS components that are in use.