Proper WP conditional tag to check for existing taxonomies to list out terms with wp_list_categories?

Question

This is what I currently have but its not rendering any results...
It was the closest conditional I could think of using to match what Im trying to output but it didnt seem to work. Any ideas?...

NOTE: The taxonomy terms that I am listing in the sidebar need to be visible at all times while viewing custom post type queries, taxonomy archives, and single product/post pages.

   <?php if (is_tax('productcategory')): ?>

        <div id="shop_by_cat">
            <?php
            echo '<ul>';
            $args_list = array(
                'taxonomy' => 'productcategory', 
                'title_li' => __(''),
                'show_count' => false,
                'hierarchical' => true,
                'echo' => '0',
            );   
            echo wp_list_categories($args_list);
            echo '</ul>';
            ?>
        </div>

    <?php else: ?>
    <?php endif; ?>

Answer 1

is_tax() returns true on a taxonomy archive page, it has nothing to do with whether terms exist in a taxonomy.

you just need to add a check for anything returned from wp_list_categories before outputting any markup:

<?php
$args_list = array(
    'taxonomy' => 'productcategory', 
    'title_li' => __(''),
    'show_count' => false,
    'hierarchical' => true,
    'echo' => '0',
);
$product_categories = wp_list_categories( $args_list );
if( $product_categories ):
    ?>
    <div id="shop_by_cat">
        <ul>
            <?php echo $product_categories; ?>
        </ul>
    </div>
    <?php
endif;
?>