Monkey patch the CSV library to add i18n support

csv_ext.rb

require 'csv'

module CoreExtensions
  module CSV
    module I18n
      # Redefine the shift method to catch the exception and attempt to return
      # a translated version of the error message using I18n.t
      def shift
        super
      rescue ::CSV::MalformedCSVError => exception
        raise $!, translated_exception_message(exception.message), $!.backtrace
      end

      private

      # Parse the exception message and attempt to translate it. If no translation
      # is possible, simply return the original error message.
      #
      # The translation keys need to be defined in your language files as follows.
      #
      #  csv:
      #    exception:
      #      field_size_exceeded: "Broken on %{line_number}"
      #      illegal_quoting:
      #      missing_or_stray_quote:
      #      unclosed_quoted_field:
      #      unquoted_fields_do_not_allow_r_or_n:
      #
      def translated_exception_message(msg)
        return msg unless defined?(I18n)

        # This will break if the CSV class changes it's error messages
        matches = msg.match(/\s[ion]{2}?\s?\(?line (\d)\)?\.?/i)
        return msg if matches.nil?

        ::I18n.t(
          keyify(msg.sub(matches[0], '')),
          scope: [:csv, :exception],
          line_number: matches[1],
          default: msg
        )
      end

      # :reek:UtilityFunction but could use parameterize('_') if rails is present
      def keyify(msg)
        msg.gsub(/[^a-z]+/i, ' ').strip.gsub(' ', '_').downcase
      end
    end
  end
end

CSV.prepend CoreExtensions::CSV::I18n