FIX: Don't remove custom fields when adding a new one to category ser…

…ializer (#150)

plugin.rb

@@ -94,7 +94,9 @@ class Engine < ::Rails::Engine
     end
   end
 
-  add_to_serializer(:category, :custom_fields) do
+  add_to_serializer(:category, :custom_fields, false) do
+    return object.custom_fields if !SiteSetting.voting_enabled
+
     object.custom_fields.merge(
       enable_topic_voting:
         DiscourseTopicVoting::CategorySetting.find_by(category_id: object.id).present?,

spec/serializers/category_serializer_spec.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+require "rails_helper"
+
+describe CategorySerializer do
+  fab!(:category) { Fabricate(:category) }
+
+  it "does not return enable_topic_voting voting disabled" do
+    SiteSetting.voting_enabled = false
+
+    json = CategorySerializer.new(category, root: false).as_json
+
+    expect(json[:custom_fields]).to eq({})
+  end
+
+  it "returns enable_topic_voting when voting enabled" do
+    SiteSetting.voting_enabled = true
+
+    json = CategorySerializer.new(category, root: false).as_json
+
+    expect(json[:custom_fields]).to eq({ "enable_topic_voting" => false })
+  end
+end