Always instantiate I18n::Locale::Fallbacks objects when using I18n.fallbacks=

[radar]

Should fix #534.

[radar]

@sshaw Would you mind trying out this branch within the next ~12ish hours? If it's fine for you and for CI, I'm happy to merge it and do a 1.8.4 release.

[sshaw]

Using the same config which, from your comments on #534 seems to be the goal, I get:

rails [5.0.7.2] (xxx)$ I18n.l Time.now, :format => :long, :locale => "XX"
Traceback (most recent call last):
       12: from ./bin/rails:4:in `<main>'
       11: from ./bin/rails:4:in `require'
       10: from /Users/sshaw/.rvm/gems/ruby-2.5.2/gems/railties-5.0.7.2/lib/rails/commands.rb:18:in `<top (required)>'
        9: from /Users/sshaw/.rvm/gems/ruby-2.5.2/gems/railties-5.0.7.2/lib/rails/commands/commands_tasks.rb:49:in `run_command!'
        8: from /Users/sshaw/.rvm/gems/ruby-2.5.2/gems/railties-5.0.7.2/lib/rails/commands/commands_tasks.rb:78:in `console'
        7: from /Users/sshaw/.rvm/gems/ruby-2.5.2/gems/railties-5.0.7.2/lib/rails/commands/console_helper.rb:9:in `start'
        6: from /Users/sshaw/.rvm/gems/ruby-2.5.2/gems/railties-5.0.7.2/lib/rails/commands/console.rb:65:in `start'
        5: from (irb):1
        4: from /Users/sshaw/.rvm/gems/ruby-2.5.2/bundler/gems/i18n-741845cfec07/lib/i18n.rb:301:in `localize'
        3: from /Users/sshaw/.rvm/gems/ruby-2.5.2/bundler/gems/i18n-741845cfec07/lib/i18n/backend/base.rb:84:in `localize'
        2: from /Users/sshaw/.rvm/gems/ruby-2.5.2/bundler/gems/i18n-741845cfec07/lib/i18n.rb:211:in `translate'
        1: from /Users/sshaw/.rvm/gems/ruby-2.5.2/bundler/gems/i18n-741845cfec07/lib/i18n.rb:373:in `handle_exception'
I18n::MissingTranslationData (translation missing: XX.time.formats.long)

Config:

require "i18n/backend/fallbacks"

I18n::Backend::Simple.send(:include, I18n::Backend::Fallbacks)
I18n.enforce_available_locales = false

[sshaw]

But...

I18n::Backend::Simple.send :include, I18n::Backend::Fallbacks
I18n.enforce_available_locales = false
I18n.fallbacks = [I18n.default_locale]

Works 🎆

One thing I do notice is the first calls to I18n.l takes maybe 4 seconds to return. Using rails-i18n too.

[radar]

@sshaw That first call to I18n.l will probably be I18n loading in your translations: ref.

[radar]

@sshaw Thanks for your patience on this one. I have just pushed 1.8.4 with the changes from this PR.