FIX: Include locale in cache key for not_found_topics (#11406)

This ensures that users are only served cached content in their own language. This commit also refactors to make use of the `Discourse.cache` framework rather than direct redis access

app/controllers/application_controller.rb

@@ -803,16 +803,13 @@ class ApplicationController < ActionController::Base
     @current_user = current_user rescue nil
 
     if !SiteSetting.login_required? || @current_user
-      key = "page_not_found_topics"
-      if @topics_partial = Discourse.redis.get(key)
-        @topics_partial = @topics_partial.html_safe
-      else
+      key = "page_not_found_topics:#{I18n.locale}"
+      @topics_partial = Discourse.cache.fetch(key, expires_in: 10.minutes) do
         category_topic_ids = Category.pluck(:topic_id).compact
         @top_viewed = TopicQuery.new(nil, except_topic_ids: category_topic_ids).list_top_for("monthly").topics.first(10)
         @recent = Topic.includes(:category).where.not(id: category_topic_ids).recent(10)
-        @topics_partial = render_to_string partial: '/exceptions/not_found_topics', formats: [:html]
-        Discourse.redis.setex(key, 10.minutes, @topics_partial)
-      end
+        render_to_string partial: '/exceptions/not_found_topics', formats: [:html]
+      end.html_safe
     end
 
     @container_class = "wrap not-found-container"

spec/requests/application_controller_spec.rb

@@ -373,7 +373,7 @@ RSpec.describe ApplicationController do
 
         it 'should handle 404 to a css file' do
 
-          Discourse.redis.del("page_not_found_topics")
+          Discourse.cache.delete("page_not_found_topics:#{I18n.locale}")
 
           topic1 = Fabricate(:topic)
           get '/stylesheets/mobile_1_4cd559272273fe6d3c7db620c617d596a5fdf240.css', headers: { 'HTTP_ACCEPT' => 'text/css,*/*,q=0.1' }
@@ -394,7 +394,8 @@ RSpec.describe ApplicationController do
       end
 
       it 'should cache results' do
-        Discourse.redis.del("page_not_found_topics")
+        Discourse.cache.delete("page_not_found_topics:#{I18n.locale}")
+        Discourse.cache.delete("page_not_found_topics:fr")
 
         topic1 = Fabricate(:topic)
         get '/t/nope-nope/99999999'
@@ -406,6 +407,13 @@ RSpec.describe ApplicationController do
         expect(response.status).to eq(404)
         expect(response.body).to include(topic1.title)
         expect(response.body).to_not include(topic2.title)
+
+        # Different locale should have different cache
+        SiteSetting.default_locale = :fr
+        get '/t/nope-nope/99999999'
+        expect(response.status).to eq(404)
+        expect(response.body).to include(topic1.title)
+        expect(response.body).to include(topic2.title)
       end
     end
   end