I have a very old install that began with 6 and is now at 8. I'm trying to get it updated to 9 but have gotten stuck with getting the upgrade_status module to work. After it was installed via composer, I get this error when navigating to the report:

The website encountered an unexpected error. Please try again later.

InvalidArgumentException: Class "\Drupal\upgrade_status\Form\UpgradeStatusForm" does not exist. in Drupal\Core\DependencyInjection\ClassResolver->getInstanceFromDefinition() (line 24 of core/lib/Drupal/Core/DependencyInjection/ClassResolver.php).

I then tried to manually install it (very hacky) in the /modules directory to no effect.

I'm not sure if my install of Drupal is hopelessly broken and stuck at 8. I appreciate any suggestions or additional info that will help me troubleshoot it.


  • I then tried to manually install it Does that mean composer require didn't work?
    – Clive
    Jan 24, 2022 at 16:53
  • I initially used composer require drupal/upgrade_status and after that it appeared in the reports page, but clicking on the link navigated to the above exception. Jan 24, 2022 at 18:32
  • Did you install it and clear cache?
    – Clive
    Jan 24, 2022 at 19:20
  • I just tried composer clear-cache (and also restarted Apache) but get the same error. However, the folders that are listed when clearing are in ~/.cache/composer/. I also have a clean Drupal 9 site in a sibling directory to the Drupal 8 site. Could having these two on the same machine be an issue? Or could a mis-configuration cause them to stomp on each other in some way? Jan 24, 2022 at 20:10
  • 1
    Hi, I guess Clive's question was: After you required upgrade_status with composer, did you install the module (from the admin interface or drush en upgrade_status) and did you clear the Drupal cache (from the admin interface or drush cr)? I don't think clearing composer cache will solve your issue.
    – misterdidi
    Jan 25, 2022 at 9:07


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