config_context_list and config_context_hash only work with .rb config files

[elyscape]

Context lists and context hashes only work with Ruby config files. Attempting to use a JSON, YAML, or TOML file or load from a hash results in an error:

irb(main):001:0> require 'mixlib/config'
=> true
irb(main):002:0> class Config
irb(main):003:1>   extend Mixlib::Config
irb(main):004:1>   config_context_list :tests, :test do
irb(main):005:2*     default :x, 5
irb(main):006:2>   end
irb(main):007:1> end
=> [#<Proc:0x00007ffb3b068d88@(irb):4>]
irb(main):008:0> puts File.read('conf.yaml')
---
tests:
  - x: 7
  - x: 14
=> nil
irb(main):009:0> Config.from_file 'conf.yaml'
ArgumentError: wrong number of arguments (given 1, expected 0)
[elided]
irb(main):010:0> Config.from_hash({ tests: [{x:7}, {x:14}] })
ArgumentError: wrong number of arguments (given 1, expected 0)
[elided]

The issue is in the from_hash method. It attempts to convert a hash into executable Ruby code and then executes it. Unfortunately, this doesn't work for context lists and hashes. Here's what it produces from the sample config above:

tests [{"x"=>7}, {"x"=>14}]

This seems like it might work but, unfortunately, config_context_list and config_context_hash do not create methods for the plural symbol that take arguments.