You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: middlewares.rb
    path of file: ./repos/dd-trace-rb/lib/datadog/tracing/contrib/rails
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

require_relative '../action_pack/utils'

module Datadog
  module Tracing
    module Contrib
      # Rails module includes middlewares that are required for Rails to be properly instrumented.
      module Rails
        # This is only here to catch errors, the Rack module does something very similar, however,
        # since it's not in the same place in the stack, when the Rack middleware is called,
        # error is already swallowed and handled by Rails so we miss the call stack, for instance.
        class ExceptionMiddleware
          def initialize(app)
            @app = app
          end

          def call(env)
            @app.call(env)
          # rubocop:disable Lint/RescueException
          # Here we really want to catch *any* exception, not only StandardError,
          # as we really have no clue of what is in the block,
          # and it is user code which should be executed no matter what.
          # It's not a problem since we re-raise it afterwards so for example a
          # SignalExce
    
          def call(env)
            @app.call(env)
          # rubocop:disable Lint/RescueException
          # Here we really want to catch *any* exception, not only StandardError,
          # as we really have no clue of what is in the block,
          # and it is user code which should be executed no matter what.
          # It's not a problem since we re-raise it afterwards so for example a
          # SignalException::Interrupt would still bubble up.
          rescue Exception => e
            span = Tracing.active_span
            if !span.nil? && ActionPack::Utils.exception_is_error?(e)
              # Only set error if it's supposed to be flagged as such
              # e.g. we don't want to flag 404s.
              # You can add custom errors via `config.action_dispatch.rescue_responses`
              span.set_error(e)

              # Some exception gets handled by Rails middleware before it can be set on Rack middleware
              # The rack span is the root span of the request and should make sure it has the full exception
              # set on it.
              env[Contrib::Rack::Ext::RACK_ENV_REQUEST_SPAN].set_error(e) if env[Contrib::Rack::Ext::RACK_ENV_REQUEST_SPAN]
            end
            raise e
          end