virtus-weirdness.rb

require "virtus"

class JsonModel
  include Virtus
end

class Node < Virtus::Attribute::Object
  attr_reader :type

  class << self
    def [](type)
      raise ArgumentError, "Child nodes may only be other JsonModel classes" unless type <= JsonModel

      @generated_class_map       ||= {}
      @generated_class_map[type] ||= Class.new(self) do
        default lambda { |m, a| type.new }

        define_method :type do
          type
        end

        define_method :coerce do |value|
          value.kind_of?(Hash) ? type.new(value) : value
        end
      end
    end
  end
end

class ChildModel < JsonModel
end

class ParentModel < JsonModel
  attribute :child,  Node[ChildModel]
  attribute :string, String
end

# This should be String, but it's a descendant of Node??
puts ParentModel.attributes[:string].class.ancestors.inspect

Hah, good work stumbling upon this!

Yup, my colleague Paul figured out it boiled down to simply having any anonymous class created from Node. I'd found my way into the TypeLookup code, but no further. DataMapper does a similar thing with Flags, but that code works correctly.

So I guess as an immediate workaround, we could use the boxed type as the primitive, thus forcing them to be unique, though this is clearly not a long term solution. I'll see what I can fathom out with a bit of hacking soon.

I'll file a bug in the interim

The bug for this is in solnic/virtus#26 .. and it is now resolved.

(Added for posterity for anyone that comes across this in google)