@wordpress/block-editor/src/hooks/generated-class-name.js

Generic block editor.

/**
 * WordPress dependencies
 */
import { addFilter } from '@wordpress/hooks';
import { hasBlockSupport, getBlockDefaultClassName } from '@wordpress/blocks';

/**
 * Override props assigned to save component to inject generated className if
 * block supports it. This is only applied if the block's save result is an
 * element and not a markup string.
 *
 * @param {Object} extraProps Additional props applied to save element.
 * @param {Object} blockType  Block type.
 *
 * @return {Object} Filtered props applied to save element.
 */
export function addGeneratedClassName( extraProps, blockType ) {
	// Adding the generated className.
	if ( hasBlockSupport( blockType, 'className', true ) ) {
		if ( typeof extraProps.className === 'string' ) {
			// We have some extra classes and want to add the default classname
			// We use uniq to prevent duplicate classnames.

			extraProps.className = [
				...new Set( [
					getBlockDefaultClassName( blockType.name ),
					...extraProps.className.split( ' ' ),
				] ),
			]
				.join( ' ' )
				.trim();
		} else {
			// There is no string in the className variable,
			// so we just dump the default name in there.
			extraProps.className = getBlockDefaultClassName( blockType.name );
		}
	}
	return extraProps;
}

addFilter(
	'blocks.getSaveContent.extraProps',
	'core/generated-class-name/save-props',
	addGeneratedClassName
);