Add support for CLDR data in `I18n::Backend::Pluralization`

[movermeyer]

What are you trying to accomplish?

Fixes https://github.com/ruby-i18n/i18n/issues/629

What approach did you choose and why?

• Dropped the incorrect special case of count == 0 using the zero key
• Added handling for CLDR's explicit 0 and 1 keys
• Added CLDR's lateral inheritance of using the other plural category

What should reviewers focus on?

This is a breaking change. Anyone using the zero key in locales that don't require the zero key will have to change the key to use the explicit "0" key instead.

Q&A

Q: Are 0 & 1 the only special cases, or can one introduce others? Perhaps 2: I have a pair of cars A: It might be allowed, depending on how you read the spec... but the spec only mentions 0 and 1, the LDML DTD only considers 0 and 1 to be valid, and CLDR has only ever used 0 and 1. I left support for arbitrary numbers out of this PR, as I figure that it would be better to be restrictive with what we accept right now. It's an easy change to accept other values if it turns out to be desirable.

The impact of these changes

Pluralization lookups will will support CLDR's data. The problematic use of the zero key will be resolved. Fixes https://github.com/ruby-i18n/i18n/issues/629

[radar]

Spec mentions:

0 | 1 | zero | one | two | few | many | other

Which, in my experience, covers languages such as Russian that have particular words for "few" and "many" vs two of a thing (iirc)

PR looks good. Thank you very much :)

[simi]

Hello!

I just faced problem when upgrading rubygems.org (https://github.com/rubygems/rubygems.org/runs/7312344176?check_suite_focus=true) since there was different text in kaminari pagination (No gems found before and Displaying all 0 gems after this change).

I was able to track down this to https://github.com/kaminari/kaminari/blob/bf20fccfdbf7d10c337aeead7ecf4f54a230a5fb/kaminari-core/config/locales/kaminari.yml#L19 and fix it (at least temporarily) in app itself by providing following in en.yml locale file.

  helpers:
    page_entries_info:
      one_page:
        display_entries:
          "0": "No %{entry_name} found"

Does it mean providing "zero" as a key for special key value was removed starting 1.11.0 (for languages having zero not part of pluralization config like en https://github.com/svenfuchs/rails-i18n/blob/f5b8ac6707243084ed5357ea4c35ab4b977235c2/lib/rails_i18n/common_pluralizations/one_other.rb#L14)?

If so, that seems like a "drastic" change actually since it is even recommended in Rails Guides and per my experience this kind of unexpected change is hard to spot by automated tests (usually I don't test those edge cases for each pluralized test). Those locales are often shipped with 3rd party gems (like kaminari in my case) as well making it totally invisible to debug.

All applications I have around right now needs to lock dependency before latest release since I would need to scan them manually to ensure all pluralizations using this zero key (custom locales, and gems locales) are handled properly in every language supported. :fearful:

Is there any chance to reconsider this and make it at least deprecated first, put under configuration flag and change the behaviour later with major release?

[movermeyer]

Does it mean providing "zero" as a key for special key value was removed starting 1.11.0 (for languages having zero not part of pluralization config like en

@simi Yes. IMO, this change should be highlighted in the CHANGELOG / release notes.

it is even recommended in Rails Guides

Thanks for the reminder. I've opened a PR to correct the docs.

[sarahraqueld]

IMO, this change should be highlighted in the CHANGELOG / release notes.

+1

[radar]

Apologies for the trouble everyone. I'll remove this with #633. There should absolutely be no breaking changes between i18n minor versions.

[radar]

I18n v1.12.0 has now been released with this rolled back.

[simi]

Thanks @radar!

Would it be welcomed to re-introduce this in small steps? I can try to prepare new version with deprecation warning for example. But I'm still afraid the impact of this change is enormous.

[radar]

@simi sure, go ahead. Can you figure out how to do the deprecation warning for 1.x, and then we’ll release this change again as a 2.x?