{%- macro render_nav(items, depth=0) %}
<ul class="md-nav {% if depth > 0 %}md-nav--nested{% endif %}">
  {%- for nav_item in items %}
  <li class="md-nav__item">
    {%- if nav_item.children %}
    <span class="md-nav__link md-nav__link--section">{{ nav_item.title }}</span>
    {{ render_nav(nav_item.children, depth + 1) }}
    {%- else %}
    <a
      href="{{ nav_item.url | url }}"
      class="md-nav__link {% if nav_item.active %}active{% endif %}"
      {% if nav_item.active %}aria-current="page"{% endif %}
    >{{ nav_item.title }}</a>
    {%- endif %}
  </li>
  {%- endfor %}
</ul>
{%- endmacro %}

<nav class="md-sidebar" id="sidebar" aria-label="Site navigation">
  <div class="md-sidebar__section">
    <div class="md-sidebar__section-title">Navigation</div>
    {{ render_nav(nav) }}
  </div>
</nav>