Rails5 fix passing Group objects array into for_projects_and_groups milestone scope

app/controllers/projects/milestones_controller.rb

@@ -123,9 +123,9 @@ class Projects::MilestonesController < Projects::ApplicationController
 
   def search_params
     if request.format.json? && @project.group && can?(current_user, :read_group, @project.group)
-      groups = @project.group.self_and_ancestors
+      groups = @project.group.self_and_ancestors_ids
     end
 
-    params.permit(:state).merge(project_ids: @project.id, group_ids: groups&.select(:id))
+    params.permit(:state).merge(project_ids: @project.id, group_ids: groups)
   end
 end

changelogs/unreleased/rails5-fix-47836.yml

@@ -0,0 +1,6 @@
+---
+title: Rails5 fix passing Group objects array into for_projects_and_groups milestone
+  scope
+merge_request: 19863
+author: Jasper Maes
+type: fixed

lib/banzai/filter/milestone_reference_filter.rb

@@ -65,7 +65,7 @@ module Banzai
         # We don't support IID lookups for group milestones, because IIDs can
         # clash between group and project milestones.
         if project.group && !params[:iid]
-          finder_params[:group_ids] = project.group.self_and_ancestors.select(:id)
+          finder_params[:group_ids] = project.group.self_and_ancestors_ids
         end
 
         MilestonesFinder.new(finder_params).find_by(params)