InvalidArgumentException: "0" is an invalid render array key

For a bug report we need technical details which explain precisely how to reproduce the bug.

In addition it is helpful to include a stack trace.

This might be related to this recent effort https://www.drupal.org/project/drupal/issues/3352256 📌 Move code from the experimental SDC module to core Fixed

But I also see a few very related issues https://www.drupal.org/project/twig_tweak/issues/3457069 🐛 drupal_view breaks in 10.3 Active
for Twig Tweak which I have on my site. But it also seems to be appearing elsewhere like https://www.drupal.org/project/adaptivetheme/issues/3460269 🐛 Error after updating to Drupal 10.3.1 Active which I don't use. So, it might not be limited to just twig_tweak users.

I was able to semi-resolve my issue by identifying a lone string in a render array on the affected page and converting it to [#markup" => "the string"]. I'm still looking for some deeper explanation for this.

Hello,
I have the same error on 10.3.1 and when donwgrade to 10.2.7 it works again.

There is part of my code :

$paragraphs['left_block'][] = $entityTypeManager->getViewBuilder('paragraph')->view($entityTypeManager->getStorage('paragraph')->load($paragraph_id), 'at_the_moment');

Then i insert this in a render array

$build['at_the_moment_block'] = [
          '#theme' => 'atm_block',
          '#elements' => [
            'paragraphs' => $paragraphs,
          ],
        ];

"atm_block" it's my custom theme

'atm_block' => array(
      'variables' => array('elements' => NULL),
      'template' => 'atm-block'
    ),

My part of twig

{% for paragraph in elements.paragraphs.left_block %}
                <li class="carousel-list-item">{{ paragraph }}</li>
            {% endfor %}

This works on 10.2.7 but i have the same error on 10.3.1.

I don't understand that the problem is on the view paragraph render array.

Thank you

Hello,
I am also facing issue after upgrade to 10.3.x form 10.2.7

Uncaught PHP Exception InvalidArgumentException: ""count" is an invalid render array key. Value should be an array but got a integer. at app\docroot\core\lib\Drupal\Core\Render\Element.php line 97.

Any support will be helpful.

Thank You.

Patch No. 17 resolved this issue for me. It should fix it for you as well.
https://www.drupal.org/project/skeletontheme/issues/3275683#comment-1565... 🐛 User error: "0" is an invalid render array key in Drupal\Core\Render\Element::children() (line 98 of core/lib/Drupal/Core/Render/Element.php) with Drupal 9.3.9 Needs review