Use more generic locale as fallback for rules (#34756)

app/javascript/mastodon/features/about/index.jsx

@@ -171,8 +171,8 @@ class About extends PureComponent {
             ) : (
               <ol className='rules-list'>
                 {server.get('rules').map(rule => {
-                  const text = rule.getIn(['translations', locale, 'text']) || rule.get('text');
+                  const text = rule.getIn(['translations', locale, 'text']) || rule.getIn(['translations', locale.split('-')[0], 'text']) || rule.get('text');
-                  const hint = rule.getIn(['translations', locale, 'hint']) || rule.get('hint');
+                  const hint = rule.getIn(['translations', locale, 'hint']) || rule.getIn(['translations', locale.split('-')[0], 'hint']) || rule.get('hint');
                   return (
                     <li key={rule.get('id')}>
                       <div className='rules-list__text'>{text}</div>

app/javascript/mastodon/features/report/rules.jsx

@@ -51,7 +51,7 @@ class Rules extends PureComponent {
               value={item.get('id')}
               checked={selectedRuleIds.includes(item.get('id'))}
               onToggle={this.handleRulesToggle}
-              label={item.getIn(['translations', locale, 'text']) || item.get('text')}
+              label={item.getIn(['translations', locale, 'text']) || item.getIn(['translations', locale.split('-')[0], 'text']) || item.get('text')}
               multiple
             />
           ))}

app/models/rule.rb

@@ -42,6 +42,6 @@ class Rule < ApplicationRecord
 
   def translation_for(locale)
     @cached_translations ||= {}
-    @cached_translations[locale] ||= translations.find_by(language: locale) || RuleTranslation.new(language: locale, text: text, hint: hint)
+    @cached_translations[locale] ||= translations.where(language: [locale, locale.to_s.split('-').first]).order('length(language) desc').first || RuleTranslation.new(language: locale, text: text, hint: hint)
   end
 end

spec/models/rule_spec.rb

@@ -36,4 +36,15 @@ RSpec.describe Rule do
         .to change { described_class.ordered.pluck(:text) }.from(%w(foo baz bar)).to(%w(foo bar baz))
     end
   end
+
+  describe '#translation_for' do
+    let!(:rule) { Fabricate(:rule, text: 'This is a rule', hint: 'This is an explanation of the rule') }
+    let!(:translation) { Fabricate(:rule_translation, rule: rule, text: 'Ceci est une règle', hint: 'Ceci est une explication de la règle', language: 'fr') }
+
+    it 'returns the expected translation, including fallbacks' do
+      expect(rule.translation_for(:en)).to have_attributes(text: rule.text, hint: rule.hint)
+      expect(rule.translation_for(:fr)).to have_attributes(text: translation.text, hint: translation.hint)
+      expect(rule.translation_for(:'fr-CA')).to have_attributes(text: translation.text, hint: translation.hint)
+    end
+  end
 end