Fix #4035: The Related Tag JSON endpoint is returning the wrong information

* Fix /related_tags.json to return a list of tags in the `other_wikis` field.

* Add support for /related_tags.xml.

app/controllers/related_tags_controller.rb

@@ -4,11 +4,7 @@ class RelatedTagsController < ApplicationController
 
   def show
     @query = RelatedTagQuery.new(query: params[:query], category: params[:category], user: CurrentUser.user)
-    respond_with(@query) do |format|
-      format.json do
-        render :json => @query.to_json
-      end
-    end
+    respond_with(@query)
   end
 
   def update

app/logical/related_tag_query.rb

@@ -1,4 +1,7 @@
 class RelatedTagQuery
+  include ActiveModel::Serializers::JSON
+  include ActiveModel::Serializers::Xml
+
   attr_reader :query, :category, :user
 
   def initialize(query: nil, category: nil, user: nil)
@@ -46,7 +49,7 @@ class RelatedTagQuery
     results
   end
 
-  def other_wiki_category_tags
+  def other_wiki_pages
     return [] unless Tag.category_for(query) == Tag.categories.copyright
 
     other_wikis = wiki_page&.tags.to_a.grep(/^list_of_/i)
@@ -56,16 +59,22 @@ class RelatedTagQuery
   end
 
   def tags_for_html
-    map_with_category_data(tags)
+    tags_with_categories(tags)
   end
 
-  def to_json
-    {:query => query, :category => category, :tags => map_with_category_data(tags), :wiki_page_tags => map_with_category_data(wiki_page_tags), :other_wikis => other_wiki_category_tags}.to_json
+  def serializable_hash(**options)
+    {
+      query: query,
+      category: category,
+      tags: tags_with_categories(tags),
+      wiki_page_tags: tags_with_categories(wiki_page_tags),
+      other_wikis: other_wiki_pages.map { |wiki| [wiki.title, tags_with_categories(wiki.tags)] }.to_h
+    }
   end
 
 protected
 
-  def map_with_category_data(list_of_tag_names)
+  def tags_with_categories(list_of_tag_names)
     Tag.categories_for(list_of_tag_names).to_a
   end
 

app/views/related_tags/_current_tags.html.erb

@@ -3,7 +3,7 @@
     <%= render "related_tags/tag_column", tags: related_tags.tags, class: "general-related-tags-column", title: related_tags.pretty_name %>
     <%= render "related_tags/tag_column", tags: related_tags.wiki_page_tags, class: "wiki-related-tags-column", title: link_to("wiki:#{related_tags.pretty_name}", show_or_new_wiki_pages_path(title: related_tags.query)) %>
 
-    <% related_tags.other_wiki_category_tags.each do |wiki| %>
+    <% related_tags.other_wiki_pages.each do |wiki| %>
       <%= render "related_tags/tag_column", tags: wiki.tags, class: "other-wiki-related-tags-column", title: link_to("wiki:#{wiki.pretty_title}", show_or_new_wiki_pages_path(title: wiki.title)) %>
     <% end %>
   <% end %>

test/unit/related_tag_query_test.rb

@@ -7,7 +7,7 @@ class RelatedTagQueryTest < ActiveSupport::TestCase
     CurrentUser.ip_addr = "127.0.0.1"
   end
 
-  context "#other_wiki_category_tags" do
+  context "#other_wiki_pages" do
     subject { RelatedTagQuery.new(query: "copyright") }
 
     setup do
@@ -17,7 +17,7 @@ class RelatedTagQueryTest < ActiveSupport::TestCase
     end
 
     should "return tags from the associated list wiki" do
-      result = subject.other_wiki_category_tags
+      result = subject.other_wiki_pages
       assert_not_nil(result[0])
       assert_equal(%w(alpha beta), result[0].tags)
     end
@@ -40,7 +40,7 @@ class RelatedTagQueryTest < ActiveSupport::TestCase
       end
 
       should "render the json" do
-        assert_equal("{\"query\":\"aaa\",\"category\":null,\"tags\":[[\"aaa\",0],[\"bbb\",0],[\"ccc\",0]],\"wiki_page_tags\":[],\"other_wikis\":[]}", @query.to_json)
+        assert_equal("{\"query\":\"aaa\",\"category\":null,\"tags\":[[\"aaa\",0],[\"bbb\",0],[\"ccc\",0]],\"wiki_page_tags\":[],\"other_wikis\":{}}", @query.to_json)
       end
     end