Challenge when using a RenderElement

First thing to say, I am not totally convinced that a) my use-case is legit, b) whether I am doing everything 'right' and c) where the fix should be done.

When I upgraded to v1.0 from the final RC I was unable to see any of my embedded entities (both in the WYSIWYG and when fully rendered).

I tracked it down to entity_embed's EntityReferenceFieldFormatter->build particularly these lines:

$build['#pre_render'][] = static::class . '::disableContextualLinks';
$build['#pre_render'][] = static::class . '::disableQuickEdit'; 

I have a custom entity that kinda works along the lines of a reusable version of Paragraphs. We call them embeddables and we have a mechanism to associate 'modifiers' with them at the point of embedding (see pull_quote.png) - in this case when a pull quote bundle is embedded the editors can pick whether the pull quote floats left, right or is in the middle (each bundle can have whatever modifiers make sense to it - it can get quite fancy). We use Entity Embed to embed these into the WYSIYWG (we also have page types that use embeddable to generate landing page ... our D7 site is rescue.org, a quick look will make things pretty obvious as to how we build our site).

Most of the complexity of the modifiers get handle in a custom EntityViewBuilder - so you pass in both the entity and the modifiers.

I decided to create a RenderElement to make the code usage easier e.g.

$build = [
        '#type' => 'embeddable',
        '#embeddable' => $embeddable,
        '#view_mode' => $view_mode,
        '#options' => $options, // array of whatever options make sense to this embeddable left, right, pink, blue etc
        '#mode' => $mode, // enabled, test or disabled
]

The RenderElement has a pre_render callback that takes the parameters passed in and ends up calling our custom EntityViewBuilder with the Embeddable entity and its modifiers (and view mode etc).

We have custom entity reference field/widget/formatters that extends the standard ones and basically handle the storage, capturing and rendering of an embeddable in the context of a 'entity reference' (like on a landing page or with entity embed). The formatter uses the RenderElement.

The challenge when we upgraded from RC to 8.1.0 was the removal of the contextual menu and the disabling of quick edit.

Inside the core render class there is this block of code:

if (isset($elements['#type']) && empty($elements['#defaults_loaded'])) {
  $elements += $this->elementInfo->getInfo($elements['#type']);
}

What this does is combines the build array generated in EntityReferenceFieldFormatter->build with the RenderElement's "info" - because they both have #pre_render entries in their respective arrays the one from the RenderElement are lost, essentially, lost because of the natural of the + operator.

Obviously, I am pretty much 100% sure core is doing the right thing ... I wondered whether the Entity Embed code was 'allowed' to add those pre_render entries where it does ... but it also seemed pretty legit. In the end I dodged my way around it, as I had already subclassed EntityReferenceFieldFormatter I just overloaded the build method and made sure my RenderElement's #pre_render was included too.

I've marked this as minor, as I doubt there are many folks doing this ... and chances are I am doing something wrong.