MultiJson.load('') behavior doesn't match JSON specification

[joshcooper]

MultiJson.load('') raises, but JSON.load('') returns nil:

require 'json'
puts JSON.load('').inspect

require 'multi_json'
MultiJson.use(:json_gem)
begin
  puts MultiJson.load('')
rescue => e
  puts e.class
end

$ bx ruby --version
ruby 2.7.6p219 (2022-04-12 revision c9c2245c0a) [x86_64-linux]
$ bx ruby test.rb 
nil
MultiJson::ParseError

MultiJson behavior was changed in 49aa2d8 to raise an error. But JSON has accepted empty string since 2011 ruby/json@0eb6ed5 Also the spec says:

A [JSON] string is a sequence of zero or more Unicode characters

[joshcooper]

It appears JSON.load accepts an empty string by default, but JSON.parse and MultiJson.load do not. Also JSON.parse can be configured to reject empty strings:

irb(main):001:0> require 'json'
=> true
irb(main):002:0> JSON.load("")
=> nil
irb(main):003:0> JSON.load("", nil, allow_blank: true)
=> nil
irb(main):004:0> JSON.load("", nil, allow_blank: false)
Traceback (most recent call last):
        ....
        3: from /home/josh/work/json/lib/json/common.rb:569:in `load'
        2: from /home/josh/work/json/lib/json/common.rb:216:in `parse'
        1: from /home/josh/work/json/lib/json/common.rb:216:in `parse'
JSON::ParserError (783: unexpected token at '')
irb(main):005:0> JSON.parse("")
Traceback (most recent call last):
        ...
        2: from /home/josh/work/json/lib/json/common.rb:216:in `parse'
        1: from /home/josh/work/json/lib/json/common.rb:216:in `parse'
JSON::ParserError (783: unexpected token at '')

I think it would be least surprising if MultiJson.load allowed an empty string like the similarly named JSON.load, but I don't know if that behavior is universal among different backends.

[sferik]

I would accept a patch to make MultiJson.load behave like JSON.load, however this would require a major version bump.