Grape Middleware for Error Reporting

endpoint.rb

module Grape
  class Endpoint
    def build_middleware_with_error_tracking
      builder = build_middleware_without_error_tracking
      builder.use(::ErrorTrackingMiddleware)

      # HAAAAACK!
      builder.instance_variable_get(:'@use').tap do |use_arr|
        middleware_proc = use_arr.delete_at(use_arr.size - 1)
        use_arr.insert(0, middleware_proc)
      end

      builder
    end

    alias_method :build_middleware_without_error_tracking, :build_middleware
    alias_method :build_middleware, :build_middleware_with_error_tracking
  end
end

grape_rollbar.rb

module GrapeRollbar
  def self.included(base)
    base.extend(ClassMethods)
  end

  module ClassMethods
    def track_errors_with_rollbar(api)
      set(:rollbar_api, api)
    end
  end
end

middleware.rb

class ErrorTrackingMiddleware < Grape::Middleware::Error
  def call!(env)
    @env = env

    # expected errors
    error = catch(:error) do
      return @app.call(env)
    end

    # send error to rollbar
    error_response(error)
  rescue StandardError => e
    # unexpected errors
    # send error to rollbar
    raise e
  end
end