RescueInstrumentation

rescue_instrumentation.rb

# This piggy-backs off RescueMiddleware by using the same exception handling
# rules you've defined using rescue_from(), and applying them to lazy fields
# (which would otherwise run after middleware has been run).
# Add this to your schema:
#
#   instrument(:field, RescueInstrumentation.new)
#
class RescueInstrumentation
  def instrument(type, field)
    old_lazy_resolve_proc = field.lazy_resolve_proc
    new_lazy_resolve_proc = ->(obj, args, ctx) {
      resolved = begin
        old_lazy_resolve_proc.call(obj, args, ctx)
      rescue StandardError => err
        attempt_rescue(err)
      end

      resolved
    }

    field.redefine do
      lazy_resolve(new_lazy_resolve_proc)
    end
  end

  private def attempt_rescue(err)
    handler = GraphSchema.send(:rescue_middleware).rescue_table[err.class]
    if handler
      message = handler.call(err)
      GraphQL::ExecutionError.new(message)
    else
      raise(err)
    end
  end

end