Error: Class "Drupal\ckeditor5\Plugin\Editor\CKEditor5" not found

I was able to reproduce this locally, but I had to explicitly go to the Patternkit settings and select CKEditor5 for the editor.

However, I wasn't able to reproduce the scenario where the setting changed automatically and broke the WYSIWYG on existing pattern blocks. These are the steps I used to attempt to reproduce that:

1. Install new Drupal 9.5.8 site using standard profile with Patternkit Beta 6
2. Enable Layout Builder, Patternkit, Patternkit Example, and CKEditor modules
3. Change Basic HTML and Full HTML formats to use CKEditor instead of CKEditor5
4. Uninstall CKEditor5 module
5. Edit Patternkit JSON Settings to use CKEditor and Full HTML format
6. Enable Layout Builder and Overrides on Basic Page content type
7. Create and publish example Basic Page Node
8. Edit the layout on the example page, and place a new "[Patternkit] Example" block with content in the WYSIWYG field
9. Save the layout and confirm expected rendering
10. Update Patternkit module to 9.1.x dev release
11. Clear caches and run database updates (None found)
12. Edit layout on example page
13. Edit example block
14. Expected to see error, but the form rendered with no issues.

In an effort to mitigate misconfigurations that would break the editorial experience with the wrong editor selected, I'm attaching a patch for testing that limits the available CKEditor options on the configuration form to only those with the necessary module enabled. It also adds validation to confirm the editor selected for the selected toolbar matches what was selected on the form.

@slucero, I'm now unable to reproduce the problem, following the steps I originally reported. :-/
Like you said, I had to explicitly go to the Patternkit settings and select CKEditor5 for the editor, then I got the error about the missing class.

I tested the patch in #4, and it works great!
- On Patternkit settings page, I could only select CKEditor 5 is ckeditor5 module was installed.
- If I did select CKEditor 5 but kept a CKEditor 4-only toolbar, the settings didn't save due to the validation error.

Sorry for the incorrect steps to reproduce. I'm not sure what happened there.

slucero → credited minsharm → .

While we can't reproduce this issue automatically, I'm going to roll in the current version of the patch for the Beta 7 release to help mitigate issues from misconfiguration of the Patternkit editor and filter format editors which can lead to a WSOD.

This patch will introduce the following changes:

• Patternkit's WYSIWYG editor options for CKEditor and CKEditor5 will only be available if the related module is enabled
• Form validation has been added to prevent saving a toolbar selection that doesn't use the selected editor

This change does not prevent failure at runtime if the configuration is already in place and invalid by some other means. I will create a follow-up issue momentarily to address that.

I've merged in this patch for the Beta 7 release, and I've documented follow-up work in 🐛 Failure when WYSIWYG and Toolbar Selection are Misconfigured Needs review .

Automatically closed - issue fixed for 2 weeks with no activity.