Block Supports: Prevent Additional CSS duplication inside Query Loop

[Mustafabharmal]

Trac ticket: https://core.trac.wordpress.org/ticket/65268

What

When a block inside a Query Loop has Additional CSS, wp_add_inline_style was called once per post in the loop, duplicating the same CSS N times.

Why

wp_render_custom_css_support_styles hooks render_block_data, which fires for every block render. wp_unique_id_from_values produces the same hash for the same block template data on every loop iteration, so the same CSS gets injected repeatedly.

How

Added a static $enqueued_class_names array. The first time a class name is seen the CSS is enqueued; subsequent renders skip it.

Gutenberg PR: WordPress/gutenberg#78282

[github-actions]

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[github-actions]

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[mukeshpanchal27]

Can you add unit tests that verify the changes?

[mukeshpanchal27]

Suggested change

	* Track which class names have already had their CSS enqueued to prevent
	* duplicate styles when the same block is rendered multiple times inside
	* a Query Loop (render_block_data fires once per loop iteration).
	*/
	* Track which class names have already had their CSS enqueued to prevent
	* duplicate styles when the same block is rendered multiple times inside
	* a Query Loop (render_block_data fires once per loop iteration).
	*/

[mukeshpanchal27]

Suggested change

	/*
	* Register and add inline style for block custom CSS.
	* The style depends on global-styles to ensure custom CSS loads after
	* and can override global styles.
	*/
	/*
	* Register and add inline style for block custom CSS.
	* The style depends on global-styles to ensure custom CSS loads after
	* and can override global styles.
	*/

[westonruter]

A static variable can be very problematic for unit tests. I don't recommend using it. I suggest instead that we look at what wp_add_inline_style() is doing under the hood. It calls WP_Styles::add_inline_style( $handle, $code ) which in turn adds the provided code to an array of existing inline styles and then passes that amended array to WP_Styles::add_data( $handle, 'after', $after ).

So I think a better approach would be to use the underlying WP_Styles::$extra array instead of a static $enqueued_class_names here:

Suggested change

	* Track which class names have already had their CSS enqueued to prevent
	* duplicate styles when the same block is rendered multiple times inside
	* a Query Loop (render_block_data fires once per loop iteration).
	*/
	static $enqueued_class_names = array();
	if ( ! isset( $enqueued_class_names[ $class_name ] ) ) {
	$enqueued_class_names[ $class_name ] = true;
	/*
	* Register and add inline style for block custom CSS.
	* The style depends on global-styles to ensure custom CSS loads after
	* and can override global styles.
	*/
	wp_register_style( 'wp-block-custom-css', false, array( 'global-styles' ) );
	wp_add_inline_style( 'wp-block-custom-css', $processed_css );
	}
	* Track which class names have already had their CSS enqueued to prevent
	* duplicate styles when the same block is rendered multiple times inside
	* a Query Loop (render_block_data fires once per loop iteration).
	*/
	$handle = 'wp-block-custom-css';
	if ( ! wp_style_is( $handle, 'registered' ) ) {
	wp_register_style( $handle, false, array( 'global-styles' ) );
	}
	$after_styles = wp_styles()->get_data( $handle, 'after' );
	if ( ! is_array( $after_styles ) ) {
	$after_styles = array();
	}
	if ( ! in_array( $processed_css, $after_styles, true ) ) {
	wp_add_inline_style( $handle, $processed_css );
	}