ExtensionDiscovery fails to scan the vfsStream filesystem for modules or profiles

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For the tests requested in #4

Also should follow the default template for an issue summary please.

Rebase on 10.1.x and made a MR.

Still needs test.

Maybe deleting the work-around in \Drupal\Tests\ckeditor5\Kernel\CKEditor5PluginManagerTest which was necessary before this fix is enough to prove it now works — maybe we don't really need explicit test coverage for such a detail? 😇

Unless it fails, of course.

😱 Which it does!

Looks like the static file cache in \Drupal\Core\Extension\ExtensionDiscovery is still a problem. There's no way to wipe that.

Worked on this again for 📌 Validate config schema definitions to prevent nonsensical definitions Needs work . I'm pretty sure I have a solution now. 🤓

Hm, looks like the CKEditor 5 plugin manager test is extra complicated due to \Drupal\ckeditor5\Plugin\CKEditor5PluginDefinition::getTypedConfig() using the (global) container, which contains some static caches that get in the way. 😬

Back to needs work to correctly reflect the current state.
I see that you also implemented this fix (or at least the \Drupal::root call) in 📌 Validate config schema definitions to prevent nonsensical definitions Needs work , does that mean we close this as a duplicate or do we want to keep this open?

We should keep this open: this issue is specifically scoped to fix this problem, in #3401837 I had no choice but to figure out a solution for this. Ideally we'd be able to remove this change from #3401837 to allow a tighter scope 😇