Hide block if no submenu in Twig

Question

I'm creating a node--page.html.twig and I'm using twig_tweak to help render a block for my sidebar to display the sub-menus. Is there a way to hide it if the page doesn't have any submenus?

Here's my code:

<div class="page-sidebar grid-3 alpha">
  <div class="sub-region page-sidebar clearfix widgets widget-sidebar">
    <div class="contextual-links-region panel-pane pane-menu-tree pane-main-menu">
    {{ drupal_entity('block', 'mainmenu', check_access=false) }}
  </div>
</div>

Is there some sort of if statement I could use to hide the block if the page has no submenu?

Thank you!

Answer 1

I generally handle this sort of thing like:

// First render my content and set it to a variable.
{% set submenu = drupal_entity('block', 'mainmenu', check_access=false)|render %}
// Next, check if the variable have content.
{% if submenu %}
  // If variable has content, render with wrapping div(s).
  <div class="my-wrapping-div">
    {{ submenu }}
  </div>
{% endif %}

It's important to render the submenu whether or not it has any displayable content to make sure it's cache settings are bubbled up.

Note: this will only work if whatever your rendering returns no html. If you're seeing some wrapping divs, etc return, but no content, you can alter your if statement like {% if submenu|striptags|trim %} to strip html and check for only content.