comments: fix visible method conflict.

Fix the `Comment#visible` method conflicting with the base class
`visible` method defined in ApplicationRecord.

app/controllers/posts_controller.rb

@@ -25,7 +25,7 @@ class PostsController < ApplicationController
       @comments = @post.comments
       @comments = @comments.includes(:creator)
       @comments = @comments.includes(:votes) if CurrentUser.is_member?
-      @comments = @comments.visible(CurrentUser.user)
+      @comments = @comments.unhidden(CurrentUser.user)
 
       include_deleted = @post.is_deleted? || (@post.parent_id.present? && @post.parent.is_deleted?) || CurrentUser.user.show_deleted_children?
       @sibling_posts = @post.parent.present? ? @post.parent.children : Post.none

app/models/comment.rb

@@ -131,8 +131,7 @@ class Comment < ApplicationRecord
     select { |comment| comment.visibility(user) == :hidden }
   end
 
-  # XXX rename
-  def self.visible(user)
+  def self.unhidden(user)
     select { |comment| comment.visibility(user) == :visible }
   end
 

app/views/comments/_index_by_post.html.erb

@@ -4,12 +4,12 @@
   <% end %>
 
   <% @posts.select(&:visible?).each do |post| %>
-    <% if post.comments.visible(CurrentUser.user).any? || post.comments.hidden(CurrentUser.user).any? %>
+    <% if post.comments.unhidden(CurrentUser.user).any? || post.comments.hidden(CurrentUser.user).any? %>
       <%= content_tag(:div, { id: "post_#{post.id}", class: ["post", *PostPresenter.preview_class(post)].join(" ") }.merge(PostPresenter.data_attributes(post))) do %>
         <div class="preview">
           <%= link_to(image_tag(post.preview_file_url), post_path(post)) %>
         </div>
-        <%= render "comments/partials/index/list", post: post, comments: post.comments.visible(CurrentUser.user).last(6), page: :comments %>
+        <%= render "comments/partials/index/list", post: post, comments: post.comments.unhidden(CurrentUser.user).last(6), page: :comments %>
       <% end %>
     <% end %>
   <% end %>