Weird error in Hash.to_json

{}.to_json()

=> "{}"

{}.to_json({})

TypeError: wrong argument type Hash (expected Data)
  from (irb):4:in `to_json'
  from (irb):4

This is in Ruby 1.8.6, Rails 2.1.1...but for some reason reloading the
source fixes it:

load '/usr/local/lib/ruby/gems/1.8/gems/activesupport-2.1.1/lib/active_support/json/encoders/hash.rb'

=> []

{}.to_json({})

=> "{}"

I'm baffled...what's a "Data" and why should to_json be expecting one?

I vaguely recall seeing something similar if you have one of the other libraries around that provide json conversions - they and ActiveSupport both try and define to_json and things end up in a mess when they both try and do it.

Fred

I found that including a line
require 'json/pure'
fixes it...apparently the regular json package (which uses a C
library) is buggy.