Oj.load may fail on custom #replace method implementation

[skryukov]

Originally, I have encountered this problem when I tried to dump and load Faraday::Header object in Oj's default mode.

Reproduction (same applies to Array and String subclasses):

require 'oj'

class SubHash < Hash
  def initialize(...)
    super
    @cache = []
  end

  def replace(*)
    @cache.clear
    super
  end
end

h = SubHash.new
h[:a] = 1
dh = Oj.dump(h)
# => "{\"^o\":\"SubHash\",\"self\":{\":a\":1},\"cache\":[]}"
Oj.load(dh)
# => undefined method `clear' for nil:NilClass

[ohler55]

I'll look into it but I thought several years ago this came up and there was a disclaimer about subclasses of primitive type or maybe some support was added for limited cases. Anyway I'll look.

[skryukov]

I have created this issue just for visibility, since personally, I use Oj::Rails.mimic_JSON to overcome this issue 😅