Discourage FilterInterface::TYPE_MARKUP_LANGUAGE filters from begin enabled when using CKEditor 5

Ever since #3273312: Upgrading from CKEditor 4 for a text format that has FilterInterface::TYPE_MARKUP_LANGUAGE filters enabled → , the original issue scope envisioned here became impossible.

But I think that 💬 Unwanted p tags added when using filter_autop Fixed shows this can still cause confusion and unwanted behavior.

Therefore I propose to rescope this to discouraging people from enabling \Drupal\filter\Plugin\FilterInterface::TYPE_MARKUP_LANGUAGE filters (see \Drupal\ckeditor5\Plugin\Validation\Constraint\FundamentalCompatibilityConstraintValidator::checkNoMarkupFilters()), and encouraging them to disable these filters if they are enabled.

So I'm proposing this:

Tried to fix CCF for #11.

CI failure

Also can the proposed solution be added to the issue summary please.

We should convert this to an MR — anybody who wants to do that? :) 🙏

MR created from #12.

The Needs Review Queue Bot → tested this issue.

While you are making the above changes, we recommend that you convert this patch to a merge request → . Merge requests are preferred over patches. Be sure to hide the old patch files as well. (Converting an issue to a merge request without other contributions to the issue will not receive credit.)

Fixed the existing MR as the tests had failed, thanks!

Thanks for fixing that @ankithashetty just fyi it was tagged for novice meaning saved for new users, based on your post history think you're good to work on non-novice issues.

Was also tagged for issue summary update so that still needs to happen.