generate hidden inputs manually to keep markup consistent

lib/active_admin/form_builder.rb

@@ -68,6 +68,15 @@ def has_many(assoc, options = {}, &block)
           has_many_form.input :_destroy, as: :boolean, wrapper_html: {class: 'has_many_delete'},
                                                        label: I18n.t('active_admin.has_many_delete')
         end
+
+        # generate a hidden input field to keep the mark up consistent
+        # to disable this, pass for_options: { include_id: false}
+        # NOTE: has_many_form is a different instance then the one defining this block...has_many_form.object_id != self.object_id
+        puts "#{has_many_form.class.name} #{has_many_form.object_id} ??? #{self} #{self.object_id}"
+        if has_many_form.object.persisted? && has_many_form.options.fetch(:include_id, true) && !has_many_form.emitted_hidden_id?
+          has_many_form.input :id, as: :hidden
+        end
+
         contents
       end