Safe monkey patched mail 2.6.4 deprecation warnings for Ruby 2.4

mail_patch.rb

# frozen_string_literal: true

unless Mail::VERSION.version == "2.6.4"
  raise "Please delete #{__FILE__}, it's not required anymore"
end

# This file monkey patches away the new deprecation warnings from Ruby 2.4.
# Lifted here:
#  * https://github.com/mikel/mail/pull/1053
#  * https://github.com/mikel/mail/pull/1058
#
# The methods have been pulled from the 2.6.4 tag and then manually patched

# rubocop:disable all
module Mail
  class AttachmentsList
    def [](index_value)
      if index_value.is_a?(Integer)
        self.fetch(index_value)
      else
        self.select { |a| a.filename == index_value }.first
      end
    end
  end

  module Multibyte #:nodoc:
    def []=(*args)
      replace_by = args.pop
      # Indexed replace with regular expressions already works
      if args.first.is_a?(Regexp)
        @wrapped_string[*args] = replace_by
      else
        result = Unicode.u_unpack(@wrapped_string)
        if args[0].is_a?(Integer)
          raise IndexError, "index #{args[0]} out of string" if args[0] >= result.length
          min = args[0]
          max = args[1].nil? ? min : (min + args[1] - 1)
          range = Range.new(min, max)
          replace_by = [replace_by].pack('U') if replace_by.is_a?(Integer)
        elsif args.first.is_a?(Range)
          raise RangeError, "#{args[0]} out of range" if args[0].min >= result.length
          range = args[0]
        else
          needle = args[0].to_s
          min = index(needle)
          max = min + Unicode.u_unpack(needle).length - 1
          range = Range.new(min, max)
        end
        result[range] = Unicode.u_unpack(replace_by)
        @wrapped_string.replace(result.pack('U*'))
      end
    end
  end

  class TestRetriever
    def find(options = {}, &block)
      options[:count] ||= :all
      options[:order] ||= :asc
      options[:what] ||= :first
      emails_index = (0...@@emails.size).to_a
      emails_index.reverse! if options[:what] == :last
      emails_index = case count = options[:count]
        when :all then emails_index
        when Integer then emails_index[0, count]
        else
          raise 'Invalid count option value: ' + count.inspect
      end
      if options[:what] == :last && options[:order] == :asc || options[:what] == :first && options[:order] == :desc
        emails_index.reverse!
      end
      emails_index.each { |idx| @@emails[idx].mark_for_delete = true } if options[:delete_after_find]
      emails = emails_index.map { |idx| @@emails[idx] }
      emails.each { |email| yield email } if block_given?
      @@emails.reject!(&:is_marked_for_delete?) if options[:delete_after_find]
      emails.size == 1 && options[:count] == 1 ? emails.first : emails
    end
  end

  class AddressContainer
    def <<(address)
      @field << address
    end
  end
end
# rubocop:enable all