WordPress shortcode example: output custom post type list by custom taxonomy

content-cpt-output-list.php

<?php
/**
 * Partial for custom_post_type_list shortcode output.
 *
 * @package ChildTheme
 */

if ( ! defined( 'ABSPATH' ) ) exit; ?>

<li><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></li>

custom_post_type_list_shortcode_func.php

<?php
/**
 * Theme shortcode for outputting custom post type list.
 *
 * This file is normally included from functions.php
 *
 * @package ChildTheme
 * @link https://codex.wordpress.org/Shortcode_API
 */

if ( ! defined( 'ABSPATH' ) ) exit;

/**
 * Output custom post type.
 * [custom_post_type_list category='category-slug']
 */
function ahd_custom_post_type_list_func( $atts ) {

  $a = shortcode_atts( array(
    'category' => '',
  ), $atts );

  $cpt_name = 'custom_post_type_name';
  $tax_name = 'custom_taxonomy_name';
  $tax_slug = $a[ 'category' ];
  $no_results_string = 'There are no results.';

  if ( $tax_slug ) {

    $args = array (
      'post_type' => $cpt_name,
      'order' => 'ASC',
      'orderby' => 'title',
      'tax_query' => array(
        array (
          'taxonomy' => $tax_name,
          'field' => 'slug',
          'terms' => $tax_slug
        )
      )
    );
        
  } else {

    $args = array (
      'post_type' => $cpt_name,
      'order' => 'ASC',
      'orderby' => 'title',
    );

  }

  $query = new WP_Query( $args );
      
  if ( $query->have_posts() ) {
        
    ob_start();
    echo '<ul>';
    while ( $query->have_posts() ) : $query->the_post();
      include get_stylesheet_directory() . '/partials/content-cpt-output-list.php';
    endwhile;
    echo '</ul>';
    wp_reset_postdata();
    $output = ob_get_clean();

  } else {
      
    $output = $no_results_string;

  }
      
  return $output;

}
add_shortcode( 'custom_post_type_list', 'ahd_custom_post_type_list_func' );