您正在使用get_posts 它返回一个帖子数组，您可以使用foreach, 但不是the_loop. 请尝试此版本的代码：

function ia_news_display_test($atts){ // [ia_news cat=\'category\' num=\'numbertodisplay\']

extract(shortcode_atts(array(
        \'cat\' => \'any\',
        \'num\' => \'2\',
        ), $atts));

$dirloop = new WP_Query( array( 
    \'post_type\' => \'ia_news\', 
    \'category_name\' => $cat,
    \'posts_per_page\' => $num,
    \'orderby\' => \'menu_order\',
    \'order\' => \'ASC\'
));

    if ($dirloop->have_posts())
    {
        $content = "<ul class=\'ia_news_list\'>\\n";
        while ( $dirloop->have_posts() ) : $dirloop->the_post();

            $file_id = get_post_meta(get_the_id(), "upload_file", true);
            $file_begin = get_post_meta(get_the_id(), "begin_date", true);
            $file_end = get_post_meta(get_the_id(), "end_date", true);

            if (\'\' != $file_end)
            {
                $file_end = " to ".$file_end;
            }
            $file_url = wp_get_attachment_url($file_id);

            if (\'\' != $file_url) 
            {   
                //CHECK FOR EXISTENCE OF FILE URL
                $content .= "<li class=\'ia_nl\'><a href=\'".$file_url."\'>".$cat." ".$file_begin.$file_end."</a></li>\\n";
            }
        endwhile;
        $content .= "</ul>\\n";
    } 
    else
    { 
        $content = "nothing";
    }
    wp_reset_postdata();

    return $content;
}

add_shortcode(\'ia_news_test\', \'ia_news_display_test\');