autonomic-block-theme/functions.php

<?php

add_action('init', 'custom_stylesheet');
 
function custom_stylesheet() {
    wp_register_style( 'custom-styles', get_template_directory_uri() . '/style.css' );
    
    /** 
     * making sure css from block styles gets loaded on front-end
     * TODO: unify both css files into one stylesheet
    */
    wp_register_style( 'block-styles', get_theme_file_uri( 'block-styles.css' ) );
}
wp_enqueue_style( 'custom-styles' );
wp_enqueue_style( 'block-styles' );


function autonomic_block_styles() {
    /**
    * Enable support for block editor styles
    * @link https://developer.wordpress.org/themes/basics/theme-functions/#theme-support-in-block-themes
	*/
	add_theme_support( 'editor-styles' );
	add_theme_support( 'wp-block-styles' );
	add_editor_style( 'block-styles.css' );
}
add_action( 'after_setup_theme', 'autonomic_block_styles' );

function autonomic_theme_scripts() {
    // this is also for block styles
    wp_enqueue_script( 'autonomic-block-styles', get_theme_file_uri( '/js/block-styles.js' ), array( 'wp-blocks', 'wp-dom-ready', 'wp-edit-post' ), filemtime( get_theme_file_uri( '/js/block-styles.js' ) ));
}
add_action( 'enqueue_block_editor_assets', 'autonomic_theme_scripts' );


// Code for enabling line breaks in post excerpts

define('EXCERPT_RARELY', '{[}]');
define('EXCERPT_BR', nl2br(PHP_EOL));

function so306588_trim_excerpt_custom($text = '')
{
    add_filter('the_content', 'so306588_trim_excerpt_custom_mark', 6);

    // get through origin filter
    $text = wp_trim_excerpt($text);

    remove_filter('the_content', 'so306588_trim_excerpt_custom_mark', 6);

    return so306588_trim_excerpt_custom_restore($text);
}

function so306588_trim_excerpt_custom_mark($text)
{
    $text = nl2br($text);
    return str_replace(EXCERPT_BR, EXCERPT_RARELY, $text);
}

function so306588_trim_excerpt_custom_restore($text)
{
    return str_replace(EXCERPT_RARELY, EXCERPT_BR, $text);
}

// remove default filter
remove_filter('get_the_excerpt', 'wp_trim_excerpt');

// add custom filter
add_filter('get_the_excerpt', 'so306588_trim_excerpt_custom');