function wp_register_anchor_support( WP_Block_Type $block_type ) {
	if ( ! block_has_support( $block_type, array( 'anchor' ) ) ) {
		return;
	}

	if ( ! isset( $block_type->attributes ) ) {
		$block_type->attributes = array();
	}

	if ( ! array_key_exists( 'anchor', $block_type->attributes ) ) {
		$block_type->attributes['anchor'] = array(
			'type' => 'string',
		);
	}
}

/**
 * Add the anchor id to the output.
 *
 * @since 7.0.0
 * @access private
 *
 * @param WP_Block_Type        $block_type       Block Type.
 * @param array<string, mixed> $block_attributes Block attributes.
 * @return array<string, string> Attributes with block anchor id.
 */
function wp_apply_anchor_support( WP_Block_Type $block_type, array $block_attributes ): array {
	if ( empty( $block_attributes ) ) {
		return array();
	}

	if ( ! block_has_support( $block_type, array( 'anchor' ) ) ) {
		return array();
	}

	if ( ! isset( $block_attributes['anchor'] ) || ! is_string( $block_attributes['anchor'] ) || '' === $block_attributes['anchor'] ) {
		return array();
	}

	return array( 'id' => $block_attributes['anchor'] );
}

// Register the block support.
WP_Block_Supports::get_instance()->register(
	'anchor',
	array(
		'register_attribute' => 'wp_register_anchor_support',
		'apply'              => 'wp_apply_anchor_support',
	)
);
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