TYPO3 Core

Hey, I couldn't reproduce this on the current main branch. This doesn't seem right, there was no such change. Deactivating/reactivating an extension doesn't do so much different than flushing the cache (+ db compare). Could you give an example on how to reproduce this step by step?

Here is a simple Description and if needed i will post a step-by-step on the weekend.

First i would create a extension by making a new folder then adding ext_emconf.php and composer.json. Then i would create my Services.yaml with just the first standard part:

services:
  _defaults:
    autowire: true
    autoconfigure: true
    public: false

Then i would setup a new Module by creating a controller and template and adding my definition to Configuration->Backend->Modules.php.
If i then try to load that Module, it won't find the controller as to be expected.
After that i would extend my Services.yaml to the following:

services:
  _defaults:
    autowire: true
    autoconfigure: true
    public: false

  Example\Example\:
    resource: '../Classes/*'

This was tested on TYPO3 v12.3.0 legacy install.

Did you define PSR-4 autoloading? This seems to be an autoloading error and not a DI cache one. I think on legacy mode extensions are scanned for classes when installed. With PSR-4 autoloading new classes should be found automatically.

Yes autoload was configured in ext_emconf.php like:

'autoload' => [
        'psr-4' => [
            'Example\\Example\\' => 'Classes',
        ],
    ],

FYI: stumbled over the same issue today in a v12.4-dev installation.