Trying capitalized version of country code when accessing I18n configuration data

lib/i18n/tasks/missing_keys.rb

@@ -79,12 +79,8 @@ def missing_plural_forest(locales, _base = base_locale)
     def required_plural_keys_for_locale(locale)
       @plural_keys_for_locale ||= {}
       return @plural_keys_for_locale[locale] if @plural_keys_for_locale.key?(locale)
-      @plural_keys_for_locale[locale] =
-        begin
-          Set.new(load_rails_i18n_pluralization!(locale)[locale.to_sym][:i18n][:plural][:keys])
-        rescue SystemCallError, IOError
-          Set.new
-        end
+
+      @plural_keys_for_locale[locale] = plural_keys_for_locale(locale)
     end
 
     # Loads rails-i18n pluralization config for the given locale.
@@ -154,5 +150,32 @@ def collapse_same_key_in_locales!(forest)
       end
       forest
     end
+
+    private
+
+    def plural_keys_for_locale(locale)
+      configuration = load_rails_i18n_pluralization!(locale)
+      if configuration[locale.to_sym].nil?
+        alternate_locale = alternate_locale_from(locale)
+        return Set.new if configuration[alternate_locale.to_sym].nil?
+
+        return set_from_rails_i18n_pluralization(configuration, alternate_locale)
+      end
+      set_from_rails_i18n_pluralization(configuration, locale)
+    rescue SystemCallError, IOError
+      Set.new
+    end
+
+    def alternate_locale_from(locale)
+      re = /(\w{2})-*(\w{2})*/
+      match = locale.match(re)
+      language_code = match[1]
+      country_code = match[2]
+      "#{language_code}-#{country_code.upcase}"
+    end
+
+    def set_from_rails_i18n_pluralization(configuration, locale)
+      Set.new(configuration[locale.to_sym][:i18n][:plural][:keys])
+    end
   end
 end

spec/missing_keys_spec.rb

@@ -0,0 +1,61 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe 'MissingKeys' do
+  describe '#required_plural_keys_for_locale(locale)' do
+    let(:task) { ::I18n::Tasks::BaseTask.new }
+
+    def configuration_from(locale)
+      {
+        "#{locale}": {
+          i18n: {
+            plural: {
+              keys: %i[one other],
+              rule: -> {}
+            }
+          }
+        }
+      }
+    end
+
+    context 'when country code is lowercase' do
+      let(:locale) { 'en-gb' }
+      let(:configuration) { configuration_from(locale) }
+
+      before do
+        allow(task).to receive(:load_rails_i18n_pluralization!).with(locale).and_return(configuration)
+      end
+
+      it 'accesses the capitalized country code key and returns a populated set' do
+        expect(task.required_plural_keys_for_locale(locale)).not_to be_empty
+      end
+    end
+
+    context 'when country code is uppercase' do
+      let(:locale) { 'en-GB' }
+      let(:configuration) { configuration_from(locale) }
+
+      before do
+        allow(task).to receive(:load_rails_i18n_pluralization!).with(locale.downcase).and_return(configuration)
+      end
+
+      it 'accesses the capitalized country code key and returns a populated set' do
+        expect(task.required_plural_keys_for_locale(locale.downcase)).not_to be_empty
+      end
+    end
+
+    context 'when locale is not present in configuration hash' do
+      let(:locale) { 'zz-zz' }
+      let(:configuration) { configuration_from('en-us') }
+
+      before do
+        allow(task).to receive(:load_rails_i18n_pluralization!).with(locale).and_return(configuration)
+      end
+
+      it 'returns an empty set' do
+        expect(task.required_plural_keys_for_locale(locale)).to be_empty
+      end
+    end
+  end
+end