FIX: tags created in secured categories should not be forbidden outside those categories

app/controllers/tags_controller.rb

@@ -127,7 +127,7 @@ class TagsController < ::ApplicationController
     category = params[:categoryId] ? Category.find_by_id(params[:categoryId]) : nil
 
     tags_with_counts = DiscourseTagging.filter_allowed_tags(
-      self.class.tags_by_count(guardian, params.slice(:limit)),
+      Tag.tags_by_count_query(params.slice(:limit)),
       guardian,
       {
         for_input: params[:filterForInput],

spec/controllers/tags_controller_spec.rb

@@ -121,6 +121,15 @@ describe TagsController do
         expect(json["results"].map{|j| j["id"]}.sort).to eq([])
         expect(json["forbidden"]).to be_present
       end
+
+      it "can return tags that are in secured categories but are allowed to be used" do
+        c = Fabricate(:private_category, group: Fabricate(:group))
+        Fabricate(:topic, category: c, tags: [Fabricate(:tag, name: "cooltag")])
+        xhr :get, :search, q: "cool"
+        expect(response).to be_success
+        json = ::JSON.parse(response.body)
+        expect(json["results"].map{|j| j["id"]}).to eq(['cooltag'])
+      end
     end
   end
 end