Opaque NoMethodError on nil when a resource-bound model's associations lack corresponding resources

[xeger]

Given the following erroneous resource definitions:

class Document < ActiveRecord::Base
  belongs_to User
end

class User < ActiveRecord::BAse
end

module Resources
  class Document
    model ::Document
  end

I would hope that praxis-mapper would check its model map for nil before calling methods and perhaps raise an easy-to-understand error such as "you're missing a resource definition, you ninny!" Instead I get a gnarly backtrace that I must decode myself:

#<NoMethodError: undefined method `properties' for nil:NilClass>
praxis-mapper-b73ad03c2606/lib/praxis-mapper/selector_generator.rb:30:in `map_property'
praxis-mapper-b73ad03c2606/lib/praxis-mapper/selector_generator.rb:21:in `block in add'
praxis-mapper-b73ad03c2606/lib/praxis-mapper/selector_generator.rb:20:in `each'
praxis-mapper-b73ad03c2606/lib/praxis-mapper/selector_generator.rb:20:in `add'
praxis-mapper-b73ad03c2606/lib/praxis-mapper/selector_generator.rb:87:in `add_association'
praxis-mapper-b73ad03c2606/lib/praxis-mapper/selector_generator.rb:33:in `map_property'
praxis-mapper-b73ad03c2606/lib/praxis-mapper/selector_generator.rb:21:in `block in add'
praxis-mapper-b73ad03c2606/lib/praxis-mapper/selector_generator.rb:20:in `each'
praxis-mapper-b73ad03c2606/lib/praxis-mapper/selector_generator.rb:20:in `add'
praxis-mapper-b73ad03c2606/lib/praxis-mapper/identity_map.rb:557:in `add_selectors'
praxis-f677785df9f2/lib/praxis/extensions/mapper_selectors.rb:12:in `set_selectors'
app/controllers/test.rb:15:in `block (2 levels) in <module:Test>'