Introduce a custom version of the enqueue_block_styles_assets function

[david-binda]

Description

The WordPress enqueue_block_styles_assets function contains a bug which may lead to fatal errors for full site editing enabled themes which register custom styles and are missing a HTML template for request (for instance 404.html). As described in #35912 and #35903

The bug was patched in WordPress core ( see https://core.trac.wordpress.org/ticket/54323 ), but since the Gutenberg
11.8.0 introduced the following line in 16633ff

add_filter( 'should_load_separate_core_block_assets', '__return_true' );

it, in my humble opinion, also should patch the issue, in order to prevent fatal errors for the themes matching the above mentioned criteria.

How has this been tested?

In the WordPress 5.8 install, I have enabled the latest version of the blockbase theme (see https://github.com/Automattic/themes/tree/trunk/blockbase ) which does not include the 404.html block-template (which is still present in the version distributed via WordPress.org themes repository).

Further, I have enabled the Gutenberg v11.8.0 and experienced a fatal error on a URL which results in 404 page, and experienced a fatal error.

Applying the patch introduced in this PR fixed the fatal error.

Screenshots

Types of changes

Introduces a custom override of the enqueue_block_styles_assets with a patch introduced to WordPress in https://core.trac.wordpress.org/changeset/51941

The original function is being unhooked from the enqueue_block_assets and the new Gutenberg override is hooked.

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• I've tested my changes with keyboard and screen readers.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR (please manually search all *.native.js files for terms that need renaming or removal).

[aristath]

Seems pretty straight-forward... basically a copy-paste of the updated function from core.
However, I think we should only do this for older versions of WP and not for versions where the core patch has already been applied. 👍

[aristath]

Shouldn't this only run if the WP version is lower than 5.8.2?
Since the patch has already been applied to core, it makes sense to only target previous versions.

Suggested change

	remove_action( 'enqueue_block_assets', 'enqueue_block_styles_assets', 30 );
	add_action( 'enqueue_block_assets', 'gutenberg_enqueue_block_styles_assets', 30 );
	if ( version_compare( get_bloginfo( 'version' ), '5.8.2', '<' ) ) {
	remove_action( 'enqueue_block_assets', 'enqueue_block_styles_assets', 30 );
	add_action( 'enqueue_block_assets', 'gutenberg_enqueue_block_styles_assets', 30 );
	}

[david-binda]

Thanks for the suggestion @aristath ! You're right, there is no need to replace the callback by the patched version, if WordPress 5.8.2 is patched.

I have addressed that by the code you are suggesting here, and have also added an extra check for making sure the callback is only being replaced when it's actually hooked (eg.: in WordPress < 5.3 and possibly when removed by developer)

[skorasaurus]

Can this be closed since the Plugin now requires WP 6.0?

[t-hamano]

Can this be closed since the Plugin #46102?

I think so too. As of the time I write this comment, the Gutenberg plugin requires WordPress 6.3.

@david-binda Thank you for your work!