class ActionDispatch::PermissionsPolicy::Middleware

def call(env)
  request = ActionDispatch::Request.new(env)
  _, headers, _ = response = @app.call(env)
  return response unless html_response?(headers)
  return response if policy_present?(headers)
  if policy = request.permissions_policy
    headers[POLICY] = policy.build(request.controller_instance)
  end
  if policy_empty?(policy)
    headers.delete(POLICY)
  end
  response
end