Improvements to locale finding

app/controllers/api/v1/locales_controller.rb

@@ -48,11 +48,13 @@ def index
       # Returns the requested language's locale strings (returns 406 if locale doesn't exist)
       def show
         language = params[:name].tr('-', '_')
+        language_file = Dir.entries('app/assets/locales').select { |f| f.starts_with?(language) }
+        final_language = language_file.min&.gsub('.json', '')
 
         # Serve locales files directly in development (not through asset pipeline)
-        return render file: Rails.root.join('app', 'assets', 'locales', "#{language}.json") if Rails.env.development?
+        return render file: Rails.root.join('app', 'assets', 'locales', "#{final_language}.json") if Rails.env.development?
 
-        redirect_to ActionController::Base.helpers.asset_path("#{language}.json")
+        redirect_to ActionController::Base.helpers.asset_path("#{final_language}.json")
       rescue StandardError
         head :not_acceptable
       end

spec/controllers/locales_controller_spec.rb

@@ -0,0 +1,47 @@
+# BigBlueButton open source conferencing system - http://www.bigbluebutton.org/.
+#
+# Copyright (c) 2022 BigBlueButton Inc. and by respective authors (see below).
+#
+# This program is free software; you can redistribute it and/or modify it under the
+# terms of the GNU Lesser General Public License as published by the Free Software
+# Foundation; either version 3.0 of the License, or (at your option) any later
+# version.
+#
+# Greenlight is distributed in the hope that it will be useful, but WITHOUT ANY
+# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+# PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License along
+# with Greenlight; if not, see <http://www.gnu.org/licenses/>.
+
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe Api::V1::LocalesController, type: :controller do
+  before do
+    request.headers['ACCEPT'] = 'application/json'
+  end
+
+  describe '#show' do
+    it 'returns the correct language file' do
+      get :show, params: { name: 'en' }
+      expect(response).to redirect_to(ActionController::Base.helpers.asset_path('en.json'))
+    end
+
+    it 'returns the correct dialect file' do
+      get :show, params: { name: 'ko_KR' }
+      expect(response).to redirect_to(ActionController::Base.helpers.asset_path('ko_KR.json'))
+    end
+
+    it 'returns the dialect language file if the regular language doesnt exist' do
+      get :show, params: { name: 'pl' }
+      expect(response).to redirect_to(ActionController::Base.helpers.asset_path('pl_PL.json'))
+    end
+
+    it 'returns not_acceptable if the language doesnt exist' do
+      get :show, params: { name: 'invalid' }
+      expect(response).to have_http_status(:not_acceptable)
+    end
+  end
+end