Leave unknown language as nil if account is remote

[tribela]

It is not reasonable to use Local instance's language setting for foreign user's toot.

[Quenty31]

I was thinking of it this very morning!

[tribela]

Can someone help me to fix test code?

  1) LanguageDetector detect when language can't be detected remote user force use detector
     Failure/Error: let(:account_remote) { Fabricate(:user, domain: 'joinmastodon.org').account }
     
     ActiveModel::UnknownAttributeError:
       unknown attribute 'domain' for User.
     # ./spec/lib/language_detector_spec.rb:45:in `block (3 levels) in <top (required)>'
     # ./spec/lib/language_detector_spec.rb:111:in `block (5 levels) in <top (required)>'

[ClearlyClaire]

I don't think we should use the language detector's result when it's unreliable. Maybe it's best to leave this field as nil?

[tribela]

When language field is nil, Is it never shown to user who filtered some languages?

[Gargron]

The language detector is super inaccurate for short messages. Also, you can't ignore when people set a posting language preference (which is hopefully more correct than the detector, although vandalism is also possible)

[tribela]

So.. It's better to set nil on foreign toot which not having language field?

[ClearlyClaire]

@Kjwon15 When a status' language is set to nil, it is always shown.

@Gargron afaict this change doesn't ignore the posting language setting, it just drops the fallback to default user / instance setting on receiving remote toots for which a language wasn't defined and for which the detection has been deemed unreliable.

[tribela]

Yes, It actually fixes a bug