Unhandled Warning: Undefined array key "translatable"

can ne merged/tagged

This fix works for me. Thank you. :)

JSchref, did you mean to erase the issue summary?

I need to check the steps to reproduce, and it would be good to have test coverage for this, as clearly there are some incorrect assumptions in the code.

I have reverted JSchref erasing of the issue summary.

I followed the 'steps to reproduce' but could not get the error. Specifically what I did was

1. Enable Scheduler
2. Enable "Content Translation" core module
3. Add a new language via /admin/config/regional/language (Config -> Region and Language -> Language )
4. Enable a content type for translation content (via Content type -> edit -> language settings -> tick both chekcboxes "Show language selector on create and edit pages" and "enable translation"
5. Save is OK, no error
6. Or if you enable you enable translation on admin/config/regional/content-language (Config -> Region and Language -> Content language and translation) - there is still no problem and no error on save

I am not saying that there is no problem, it is just that there must be something else in your set-up which is causing this error. I need to understand what is causing the problem and replicate it, before committing any fix.

On 🐛 Undefined array key "translatable" in _scheduler_translation_validate() (line 732 of modules/contrib/scheduler/scheduler.module) Active I was able to replicate the error, the key difference is that Language needs to be installed but not Content Translation. I am going to see if I can add some simple test coverage for this.

I have added a simple test to make sure the Content Language form can be saved even when the Translation module is not enabled.
https://git.drupalcode.org/project/scheduler/-/pipelines/393018
The "test only changes" job shows that we do now have coverage for this, because the new test fails when the fix is reverted.