require_or_load

# File activesupport/lib/active_support/dependencies.rb, line 385
    def require_or_load(file_name, const_path = nil)
      file_name = file_name.chomp(".rb")
      expanded = File.expand_path(file_name)
      return if loaded.include?(expanded)

      Dependencies.load_interlock do
        # Maybe it got loaded while we were waiting for our lock:
        return if loaded.include?(expanded)

        # Record that we've seen this file *before* loading it to avoid an
        # infinite loop with mutual dependencies.
        loaded << expanded
        loading << expanded

        begin
          if load?
            # Enable warnings if this file has not been loaded before and
            # warnings_on_first_load is set.
            load_args = ["#{file_name}.rb"]
            load_args << const_path unless const_path.nil?

            if !warnings_on_first_load || history.include?(expanded)
              result = load_file(*load_args)
            else
              enable_warnings { result = load_file(*load_args) }
            end
          else
            result = require file_name
          end
        rescue Exception
          loaded.delete expanded
          raise
        ensure
          loading.pop
        end

        # Record history *after* loading so first load gets warnings.
        history << expanded
        result
      end
    end