Improve the localization concern, moving to around_action

.template/spec/base/app/controllers/concerns/localization_spec.rb

@@ -0,0 +1,7 @@
+describe 'localization concern' do
+  subject { file('app/controllers/concerns/localization.rb') }
+
+  it 'contains the around_action' do
+    expect(subject).to contain('around_action :switch_locale')
+  end
+end

.template/spec/base/config/environments/production_spec.rb

@@ -8,6 +8,14 @@
   it 'configures the mailer default url options' do
     expect(subject).to contain(mailer_default_url_config)
   end
+
+  it 'adds the i18n configuration' do
+    expect(subject).to contain(i18n_config)
+  end
+
+  it 'removes the config.i18n.fallbacks = true' do
+    expect(subject).not_to contain("config.i18n.fallbacks = true")
+  end
 
   it 'allows Rails serve static file' do
     expect(subject).to contain('config.public_file_server.enabled = true')
@@ -23,4 +31,17 @@ def mailer_default_url_config
       }
     EOT
   end
+
+  def i18n_config
+    <<~EOT
+      # eg: AVAILABLE_LOCALES = 'en,th'
+      config.i18n.available_locales = ENV.fetch('AVAILABLE_LOCALES').split(',')
+
+      # eg: DEFAULT_LOCALE = 'en'
+      config.i18n.default_locale = ENV.fetch('DEFAULT_LOCALE')
+
+      # eg: FALLBACK_LOCALES = 'en,th'
+      config.i18n.fallbacks = ENV.fetch('FALLBACK_LOCALES').split(',')
+    EOT
+  end
 end

.template/variants/api/app/controllers/concerns/localization.rb

@@ -2,12 +2,20 @@ module Localization
   extend ActiveSupport::Concern
 
   included do
-    before_action :set_locale
+    around_action :switch_locale
 
     protected
 
-    def set_locale
-      I18n.locale = request.headers[:'Accept-Language'] || I18n.default_locale
+    def switch_locale(&action)
+      locale = extract_locale_from_header || I18n.default_locale
+
+      I18n.with_locale(locale, &action)
+    end
+
+    def extract_locale_from_header
+      return request.headers[:'Accept-Language'] if I18n.locale_available?(request.headers[:'Accept-Language'])
+
+      nil
     end
   end
 end

.template/variants/web/app/controllers/concerns/localization.rb

@@ -2,12 +2,20 @@ module Localization
   extend ActiveSupport::Concern
 
   included do
-    before_action :set_locale
+    around_action :switch_locale
 
     protected
 
-    def set_locale
-      I18n.locale = params[:locale] || I18n.default_locale
+    def switch_locale(&action)
+      locale = extract_locale_from_param || I18n.default_locale
+
+      I18n.with_locale(locale, &action)
+    end
+
+    def extract_locale_from_param
+      return params[:locale] if I18n.locale_available?(params[:locale])
+
+      nil
     end
 
     private

config/application.yml.tt

@@ -6,6 +6,9 @@ default: &default
   MAILER_DEFAULT_HOST: "localhost"
   MAILER_DEFAULT_PORT: "3000"
   MAILER_SENDER: "Test <noreply@nimblehq.co>"
+  AVAILABLE_LOCALES: "en"
+  DEFAULT_LOCALE: "en"
+  FALLBACK_LOCALES: "en"
 
 development:
   <<: *default

config/environments/production.rb

@@ -12,3 +12,22 @@
   }
   EOT
 end
+
+# Remove the incorrect fallback configuration (was generated by Rails)
+# https://github.com/ruby-i18n/i18n/releases/tag/v1.1.0
+gsub_file('config/environments/production.rb', 'config.i18n.fallbacks = true', '')
+
+# Adding the correct fallback configuration along with default locale and available locales
+environment do
+  <<~EOT
+    # eg: AVAILABLE_LOCALES = 'en,th'
+    config.i18n.available_locales = ENV.fetch('AVAILABLE_LOCALES').split(',')
+
+    # eg: DEFAULT_LOCALE = 'en'
+    config.i18n.default_locale = ENV.fetch('DEFAULT_LOCALE')
+
+    # eg: FALLBACK_LOCALES = 'en,th'
+    config.i18n.fallbacks = ENV.fetch('FALLBACK_LOCALES').split(',')
+
+  EOT
+end