vagrant/plugins/provisioners/file/config.rb

require "vagrant"

module VagrantPlugins
  module FileUpload
    class Config < Vagrant.plugin("2", :config)
      attr_accessor :source
      attr_accessor :destination

      def validate(machine)
        errors = _detected_errors
        if !source
          errors << I18n.t("vagrant.provisioners.file.no_source_file")
        end
        if !destination
          errors << I18n.t("vagrant.provisioners.file.no_dest_file")
        end
        if source
          s = File.expand_path(source)
          if ! File.exist?(s)
            errors << I18n.t("vagrant.provisioners.file.path_invalid",
                              path: s)
          end
        end

        { "File provisioner" => errors }
      end
    end
  end
end