Fix calendar feed when sorted by priority

app/views/issues/_issues_calendar.ics.ruby

@@ -3,7 +3,7 @@ cal.prodid = '-//GitLab//NONSGML GitLab//EN'
 cal.x_wr_calname = 'GitLab Issues'
 
 # rubocop: disable CodeReuse/ActiveRecord
-@issues.includes(project: :namespace).each do |issue|
+@issues.preload(project: :namespace).each do |issue|
   cal.event do |event|
     event.dtstart     = Icalendar::Values::Date.new(issue.due_date)
     event.summary     = "#{issue.title} (in #{issue.project.full_path})"

changelogs/unreleased/54146-fix-calendar-query.yml

+---
+title: Fix project calendar feed when sorted by priority
+merge_request: 23870
+author:
+type: fixed

spec/features/ics/project_issues_spec.rb

@@ -72,5 +72,14 @@ describe 'Project Issues Calendar Feed'  do
         expect(body).to have_text('TRANSP:TRANSPARENT')
       end
     end
+
+    context 'sorted by priority' do
+      it 'renders calendar feed' do
+        visit project_issues_path(project, :ics, sort: 'priority', feed_token: user.feed_token)
+
+        expect(response_headers['Content-Type']).to have_content('text/calendar')
+        expect(body).to have_text('BEGIN:VCALENDAR')
+      end
+    end
   end
 end