JSON.generate ignores to_json method inside Fixnum or Bignum

[sproot]

Here is an example:

> (1..4).to_json
=> "[\"1..4\"]" 
> JSON.generate [1..4]
=> "[\"1..4\"]" 

class Range
  def to_json(*a)
    {
      'json_class'   => self.class.name, # = 'Range'
      'data'         => [ first, last, exclude_end? ]
    }.to_json(*a)
  end
end

> (1..4).to_json
=> "{\"json_class\":\"Range\",\"data\":[1,4,false]}" 
> JSON.generate [1..4]
=> "[{\"json_class\":\"Range\",\"data\":[1,4,false]}]" 

So to_json works well with Range class. But let's try it with Fixnum

1.to_json
=> "1" 
>  JSON.generate [1]
=> "[1]" 

class Fixnum
  def to_json(*a)
    { value: self.to_s }.to_json(*a)
  end
end

> 1.to_json
=> "{\"value\":\"1\"}" 
>  JSON.generate [1]
=> "[1]" 

WAT? Why do we have different behaviour for integers? :(

[marcandre]

I confirm that this bug is still present. It affects the C implementation, but not json/pure. This is due to an optimization that should check if the builtin method has been redefined or not. (did not check Java port)

[byroot]

I'm afraid checking for that would really kill performance, so while I understand one might expect this behavior, I don't think it's desirable to handle it.