Undefined array key "type" in Drupal\Core\Theme\ThemeManager->render()

Fixes are made on on 11.x (our main development branch) first, and are then back ported as needed according to our policies. Also, 10.2 is in security mode now.

Hi @dmytro.chornyi,

I verified it both in 10.2.x and 11.x, i am not able to reproduce it at my end, I added following code in sites/development.services.yml

twig.config:
    debug: true
    auto_reload: true

Also checked all the check-boxes on admin/config/development/settings page. Adding screenshot for the reference.

It might me the Theme issue. Can you please share all the details like the theme name etc.

Thanks
Samit K.

Don't know if this is relevant but here's a quick fix that worked for me. I'm on Drupal 10.3.1 though, and I faced this exact warning while customising the default user login page using hook_theme_suggestions_alter() and hook_theme_registry_alter(), but this might help others as well, if you are in similar endeavour.

<?php
$theme_registry['page__custom_page']['type'] = 'base_theme_engine';

Setting the type key for the theme suggestion directly in the theme registry resolves it.

Cheers :)
Malhar

Since there's been no follow up to reproduce this going to close out. If still an issue in D11 please re-open updating summary.

I am also getting this warning after updated to d11 latest.

In custom module I define hook_theme() and there custom theme hooks with template names. However it warns me about empty template and next render chain is failing

The website encountered an unexpected error. Try again later.

Twig\Error\LoaderError: Template "modules/custom/mymodule/templates/.html.twig" is not defined. in Twig\Loader\ChainLoader->getCacheKey() (line 111 of /var/www/vhosts/myhost/httpdocs/updates/vendor/twig/twig/src/Loader/ChainLoader.php).
Twig\Environment->getTemplateClass() (Line: 204)
Drupal\Core\Template\TwigEnvironment->getTemplateClass() (Line: 370)
Twig\Environment->load() (Line: 34)
twig_render_template() (Line: 380)
Drupal\Core\Theme\ThemeManager->render() (Line: 497)
Drupal\Core\Render\Renderer->doRender() (Line: 227)
Drupal\Core\Render\Renderer->render() (Line: 242)
Drupal\Core\Render\MainContent\HtmlRenderer->Drupal\Core\Render\MainContent\{closure}() (Line: 627)
Drupal\Core\Render\Renderer->executeInRenderContext() (Line: 235)
Drupal\Core\Render\MainContent\HtmlRenderer->prepare() (Line: 131)
Drupal\Core\Render\MainContent\HtmlRenderer->renderResponse() (Line: 90)
Drupal\Core\EventSubscriber\MainContentViewSubscriber->onViewRenderArray() (Line: 246)
Symfony\Component\EventDispatcher\EventDispatcher::Symfony\Component\EventDispatcher\{closure}() (Line: 206)
Symfony\Component\EventDispatcher\EventDispatcher->callListeners() (Line: 56)
Symfony\Component\EventDispatcher\EventDispatcher->dispatch() (Line: 188)
Symfony\Component\HttpKernel\HttpKernel->handleRaw() (Line: 76)
Symfony\Component\HttpKernel\HttpKernel->handle() (Line: 53)
Drupal\Core\StackMiddleware\Session->handle() (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle() (Line: 28)
Drupal\Core\StackMiddleware\ContentLength->handle() (Line: 32)
Drupal\big_pipe\StackMiddleware\ContentLength->handle() (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle() (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle() (Line: 53)
Drupal\Core\StackMiddleware\AjaxPageState->handle() (Line: 51)
Drupal\Core\StackMiddleware\StackedHttpKernel->handle() (Line: 715)
Drupal\Core\DrupalKernel->handle() (Line: 19)

This was working on drupal 9.5 before