What if any design issues are there in this method of loading configuration data from YAML in Ruby?
You use eval, but eval is evil.

I tried a solution without eval. For this I used:


Module.const_set to define constants
Module.const_defined to check if a constant is defined
Module.const_get to navigate inside modules
Module.new to define new modules.


My solution (including a little test):

def def_constants!(hash, context)

  #context should be a module. If not, then get (or build) it.
  if context.is_a? String 
      lcontext = Object
      context.split('::').each{ |module_name| 
        lcontext.const_set(module_name, Module.new) unless lcontext.const_defined?(module_name)
        lcontext = lcontext.const_get(module_name)
      }
    context = lcontext
  end

  raise ArgumentError unless context.is_a?(Module)

  hash.each do |key, value|
    case value
      when Hash
        module_name = key.upcase #fixme --  convert_string_to_camel_case(key)
        def_constants!( hash[key], [context.name, module_name].join('::'))
      when /::/  # explicitly build out this module (since it doesn't exist) so that we can talk about it
        context.const_set(key.upcase, Module.new)
        lmod = context.const_get(key.upcase)
        value.split('::').each{ |module_name| 
          lmod = lmod.const_set(module_name, Module.new )
        }
      else
        # define the given constant
        context.const_set(key.upcase, value)
    end
  end #hash
end

module AA #define a start
end

require 'yaml'
def_constants!(YAML.load(DATA), AA)
p AA.constants
p AA::KEY
p AA::SAMPLE_MODULE::SOME_KEY
p AA::KEY_SHOULD_BE_MODULE
p AA::KEY_SHOULD_BE_MODULE::I
p AA::KEY_SHOULD_BE_MODULE::I.constants
p AA::KEY_SHOULD_BE_MODULE::I::Am
p AA::KEY_SHOULD_BE_MODULE::I::Am::A
p AA::KEY_SHOULD_BE_MODULE::I::Am::A::Module


__END__
key: value
numeric_data: 3.221
sample_module:
    some_key: another value
key_should_be_module: I::Am::A::Module


I haven't tested it for each usecase. I expect problems, when you try to define modules, where you have already constants with the same name.

Some changes, to use it in your code:


I skipped convert_string_to_camel_case(key) and replaced it with upcase
Your @project_name is my initial context.
(and sure: I renamed the method ;-) )