Render the page in the user's preferred locale

We add new method set_user_locale to render the page
with the user's preferred locale.

Note that we add a condition 'if params[:locale].blank?'
to recover the user's preferred locale. This is necessary
because it may be the case that the user does not have an
associated locale, and when execute '@user.locale' when
this value is 'nil', by default returns the default locale.
As we do not want this to happen and we want the locale we
receive as parameter to prevail in this case.

app/controllers/subscriptions_controller.rb

@@ -1,5 +1,5 @@
 class SubscriptionsController < ApplicationController
-  before_action :set_user
+  before_action :set_user, :set_user_locale
   skip_authorization_check
 
   def edit
@@ -28,4 +28,11 @@ class SubscriptionsController < ApplicationController
     def allowed_params
       [:email_on_comment, :email_on_comment_reply, :email_on_direct_message, :email_digest, :newsletter]
     end
+
+    def set_user_locale
+      if params[:locale].blank?
+        I18n.locale = I18n.available_locales.find { |locale| locale == @user.locale&.to_sym }
+        session[:locale] = I18n.locale
+      end
+    end
 end

spec/controllers/subscriptions_controller_spec.rb

@@ -12,5 +12,12 @@ describe SubscriptionsController do
       expect(response).to redirect_to "/"
       expect(flash[:alert]).to eq "You do not have permission to access this page."
     end
+
+    it "shows the 'not allowed' message in the current locale" do
+      get :edit, params: { token: "", locale: :es }
+
+      expect(response).to redirect_to "/"
+      expect(flash[:alert]).to eq "No tienes permiso para acceder a esta página."
+    end
   end
 end

spec/system/subscriptions_spec.rb

@@ -3,6 +3,28 @@ require "rails_helper"
 describe "Subscriptions" do
   let(:user) { create(:user, subscriptions_token: SecureRandom.base58(32)) }
 
+  context "Edit page" do
+    scenario "Render content in the user's preferred locale" do
+      user.update!(locale: "es")
+      visit edit_subscriptions_path(token: user.subscriptions_token)
+
+      expect(page).to have_content "Notificaciones"
+      expect(page).to have_field "Recibir un email cuando alguien comenta en mis propuestas o debates",
+                                  type: :checkbox
+      expect(page).to have_field "Recibir un email cuando alguien contesta a mis comentarios", type: :checkbox
+      expect(page).to have_field "Recibir emails con información interesante sobre la web", type: :checkbox
+      expect(page).to have_field "Recibir resumen de notificaciones sobre propuestas", type: :checkbox
+      expect(page).to have_field "Recibir emails con mensajes privados", type: :checkbox
+      expect(page).to have_button "Guardar cambios"
+    end
+
+    scenario "Use the locale in the parameters when accessing anonymously" do
+      visit edit_subscriptions_path(token: user.subscriptions_token, locale: :es)
+
+      expect(page).to have_content "Notificaciones"
+    end
+  end
+
   context "Update" do
     scenario "Allow updating the status notification" do
       user.update!(email_on_comment: false,