"Failed to start the session because headers have already been sent" - while indexing
>>> [!note] Migrated issue
<!-- Drupal.org comment -->
<!-- Migrated from issue #3605600. -->
Reported by: [achap](https://www.drupal.org/user/3200249)
Related to !18
>>>
<h3 id="summary-problem-motivation">Problem/Motivation</h3>
<p>While indexing a page I get an error <code>"RuntimeException while trying to render item entity:node/10006:de with view mode search_index for search index Index A: Failed to start the session because headers have already been sent by "/app/vendor/symfony/http-foundation/Response.php" at line 1285. in Symfony\Component\HttpFoundation\Session\Storage\NativeSessionStorage->start() (line 116 of /app/vendor/symfony/http-foundation/Session/Storage/NativeSessionStorage.php)."</code></p>
<p>The stack trace indicates this starts in <code>CookiePreviewDetector::isPreviewing</code> method.</p>
<pre>#0 /app/docroot/core/lib/Drupal/Core/Session/SessionManager.php(129): Symfony\Component\HttpFoundation\Session\Storage\NativeSessionStorage->start()<br>#1 /app/docroot/core/lib/Drupal/Core/Session/SessionManager.php(94): Drupal\Core\Session\SessionManager->startNow()<br>#2 /app/vendor/symfony/http-foundation/Session/Storage/NativeSessionStorage.php(282): Drupal\Core\Session\SessionManager->start()<br>#3 /app/vendor/symfony/http-foundation/Session/Session.php(201): Symfony\Component\HttpFoundation\Session\Storage\NativeSessionStorage->getBag('attributes')<br>#4 /app/vendor/symfony/http-foundation/Session/Session.php(221): Symfony\Component\HttpFoundation\Session\Session->getBag('attributes')<br>#5 /app/vendor/symfony/http-foundation/Session/Session.php(69): Symfony\Component\HttpFoundation\Session\Session->getAttributeBag()<br>#6 /app/docroot/modules/contrib/entity_reference_preview/src/Plugin/PreviewDetector/CookiePreviewDetector.php(51): Symfony\Component\HttpFoundation\Session\Session->get('entity_referenc...')<br>#7 /app/docroot/modules/contrib/entity_reference_preview/src/Cache/StatusPreviewCacheContext.php(68): Drupal\entity_reference_preview\Plugin\PreviewDetector\CookiePreviewDetector->isPreviewing(Object(Symfony\Component\HttpFoundation\Request))<br>#8 [internal function]: Drupal\entity_reference_preview\Cache\StatusPreviewCacheContext->Drupal\entit</pre><h4 id="summary-steps-reproduce">Steps to reproduce</h4>
<p>Set up Search API.<br>
Enable this module.<br>
Used the rendered output plugin in your search index.<br>
Check the logs.</p>
<h3 id="summary-proposed-resolution">Proposed resolution</h3>
<p>We should check that the session is actually started before trying to access the cookie. That gets rid of the error for me. If it hasn't just return FALSE. I don't think returning FALSE really matters in search index because you only want to render default revision content.</p>
<h3 id="summary-remaining-tasks">Remaining tasks</h3>
<p>N/A</p>
<h3 id="summary-ui-changes">User interface changes</h3>
<p>N/A</p>
<h3 id="summary-api-changes">API changes</h3>
<p>N/A</p>
<h3 id="summary-data-model-changes">Data model changes</h3>
<p>N/A</p>
issue
GitLab AI Context
Project: project/entity_reference_preview
Instance: https://git.drupalcode.org
Repository: https://git.drupalcode.org/project/entity_reference_preview
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