FIX: Prevent discourse_reactions from overriding topic_view.posts preloads (#36041)

Meta:
https://meta.discourse.org/t/tl-lang-crawler-view-not-showing-posts-in-lang/388443/6

When loading topics at `/t/:id` we use the `topic_view` and have some
preloads:

https://github.com/discourse/discourse/blob/d4313be4859bd07d95c620b15179424a87d94ddd/lib/topic_view.rb#L925-L939

Unfortunately these preloads have been overridden in reaction's
`TopicViewSerializer` as overriding posts with a new `post.includes`
would create a new query, so we're using `Preloader` here to preserve
existing associations.

lib/topic_view.rb

@@ -929,9 +929,8 @@ class TopicView
         :deleted_by,
         :incoming_email,
         :image_upload,
-        :localizations,
       )
-
+    @posts = @posts.includes(:localizations) if SiteSetting.content_localization_enabled
     @posts = @posts.includes({ user: :user_status }) if SiteSetting.enable_user_status
 
     @posts = apply_default_scope(@posts)

plugins/discourse-reactions/lib/discourse_reactions/posts_reaction_loader.rb

@@ -3,7 +3,13 @@
 module DiscourseReactions::PostsReactionLoader
   def posts_with_reactions
     if SiteSetting.discourse_reactions_enabled
-      posts = object.posts.includes(:post_actions, reactions: { reaction_users: :user })
+      posts = object.posts
+
+      ActiveRecord::Associations::Preloader.new(
+        records: posts,
+        associations: [:post_actions, { reactions: { reaction_users: :user } }],
+      ).call
+
       post_ids = posts.map(&:id).uniq
       posts_reaction_users_count = TopicViewSerializer.posts_reaction_users_count(post_ids)
       post_actions_with_reaction_users =
@@ -14,8 +20,6 @@ module DiscourseReactions::PostsReactionLoader
         post.reaction_users_count = posts_reaction_users_count[post.id].to_i
         post.post_actions_with_reaction_users = post_actions_with_reaction_users[post.id] || {}
       end
-
-      object.instance_variable_set(:@posts, posts)
     end
   end
 end