[BUG] Field languages in model Page may be inconsistent

[jrief]

Description

I currently have no receipt to reproduce this, but apparently we have an inconsistency in our database regarding the field languages in model Page.

Steps to reproduce

This currently is not reproducible, but I can explain what is happening using the Django shell:

>>> from cms.models.pagemodel import *
>>> page = Page.objects.get(id=21179)
>>> page.languages
'de'
>>> page.get_content_obj('de').language
'de'
>>> page.get_content_obj('en').language
'en'

Expected behaviour

Since the German and English page content objects are published, I would expect that page.languages == 'de,en'

Actual behaviour

page.languages == 'de'

Additional information (CMS/Python/Django versions)

Django-CMS-4.1.1

Do you want to help fix this issue?

Since this field is non-normalized, at least there should be a management command to fix it in case of data corruption.

• [x] Yes, I want to help fix this issue and I will join the channel #pr-reviews on the Discord Server to confirm with the community that a PR is welcome.
• [ ] No, I only want to report the issue.

[fsbraun]

I fear versioning might interfere with the proper update of the languages field. The information is clearly redundant and was a performance compromise in v3. Have you checked if list(page_obj.page_content_cache.keys()) would work for you? If so, we consider should

• replace the languages field by a @property
• replace the get_languages by the above expression

As long as you are at least accessing one language, this does not create additional database queries.

[fsbraun]

Something like this for the Page model - the languages field would be removed then:

def get_languages(self):
    self._get_page_content_cache(None, False, False)
    return list(self.page_content_cache.keys())

@property
def languages(self):
   return ",".join(self.get_languages())

[jrief]

if this doesn't hurt performance, it certainly would be a better solution.

What about using @cached_property?