Fixing memoization issues in Ruby 2.4.x

fix_yaml_column.rb

# FILE: config/initializers/fix_yaml_column.rb

# serializes the columns that break because of memoized cache
#
# alternatively, we could have just removed the string for the memoized cache, but that sounded too dangerous

# hard-require to load the class
require 'active_record/coders/yaml_column'

class ActiveRecord::Coders::YAMLColumn
  private

  def yaml_load(payload)
    ["ThreadSafe::Cache", "Monitor", "Thread::Mutex"].each do |thing_to_remove|
      payload.gsub!("!ruby/object:#{thing_to_remove}", "")
    end

    # make the main object a hash
    ["Memoizable::Memory"].each do |thing|
      payload.gsub!(thing, "Hash")
    end

    # remove the memoized_method_cache so that the memoized gem doesn't try to use it as its cache
    #
    # use a trailing : so that we don't have repeating if we gsub again
    payload.gsub!("_memoized_method_cache:", "_memoized_method_cache_hack:")

    if !ActiveRecord::Base.use_yaml_unsafe_load
      YAML.safe_load(payload, permitted_classes: ActiveRecord::Base.yaml_column_permitted_classes, aliases: true)
    else
      if YAML.respond_to?(:unsafe_load)
        YAML.unsafe_load(payload)
      else
        YAML.load(payload)
      end
    end
  end
end

memoized_cache_sanitizer.rb

# FILE: lib/memoized_cache_sanitizer.rb

# a helper module to sanitize object before serialization
module MemoizedCacheSanitizer
  REMOVE_INSTANCE_VARIABLE = :@_memoized_method_cache

  def self.sanitize(obj)
    return obj if obj.nil? || obj.instance_of?(Hash) || obj.instance_of?(Array)

    attributes = obj.instance_variables.each_with_object({}) do |iv, h|
      attr_name = iv.to_s[1..-1].to_sym
      h[attr_name] = obj.send(attr_name) unless REMOVE_INSTANCE_VARIABLE == iv
    end

    attrs = attributes.delete(:attrs).with_indifferent_access

    # build the new object with the sanitized attributes
    obj.class.new(attrs).tap do |o|
      attributes.each do |k, v|
        o.instance_variable_set(:"@#{k}", v)  # use attribue setter to avoid memoization
      end
    end
  end
end