app/views/catalog/_sort_widget.html.erb
<% if show_sort_and_per_page? and active_sort_fields.many? %>
<div id="sort-dropdown" class="sort-dropdown btn-group">
<button type="button" class="btn btn-outline-secondary dropdown-toggle" data-toggle="dropdown" data-display="static" aria-expanded="false">
<%= t('blacklight.search.sort.label', field: sort_field_label(current_sort_field.key)) %> <span class="caret"></span>
</button>
<div class="dropdown-menu dropdown-menu-right dropdown-menu-md-left" role="menu">
<%- active_sort_fields.each do |sort_key, field_config| %>
<%= link_to(sort_field_label(sort_key), url_for(search_state.params_for_search(sort: sort_key)), class: 'dropdown-item') %>
<%- end -%>
</div>
</div>
<% end %>