#plugin

My suspicion is this is about annotations not being parsed correctly. If this issue happens to anyone else, please test out the suggestion at the end of #39.

The strange thing is, that the error then occured at the same time on the production site, although I haven't changed anything there!

That confirms my suspicion that this is about something outside the Drupal database, like PHP caches for example.

My issue has been resolved by downgrading to
composer require doctrine/deprecations:1.1.3
🐛 Class "Doctrine\Deprecations\Deprecation" not found Active
All issues on all versions of php have been resolved.

After one month the error occured again, but under different circumstances:
I updated core and some modules on a local machine and pushed the changes to the webserver to a staging installation, which is a copy of the production site on the same server. After doing composer install I got this white screen:

Error: Call to a member function setFormClass() on null in /xxx/web/core/modules/action/action.module on line 48

The strange thing is, that the error then occured at the same time on the production site, although I haven't changed anything there! After clearing the cache on the production site the error changed to the one we know:

Uncaught PHP Exception Drupal\\Component\\Plugin\\Exception\\PluginNotFoundException: "The "text_default" plugin does not exist. Valid plugin IDs for Drupal\\Core\\Field\\FormatterPluginManager are: string" at /xxx/web/core/lib/Drupal/Component/Plugin/Discovery/DiscoveryTrait.php line 53

Clearing the cache again and deleting the vendor and web folders didn't have any effect his time, only after doing a cron run I could access the website again. Although I did the cron only on the production site, the staging site was also accessible again! On both sites I had now the errors attached in the screenshot. After clearing the cache on both sites they finally disappeared.