Bypass the DataMapper's infinite loop bug, described at http://datamapper.lighthouseapp.com/projects/20609/tickets/1431-stack-level-too-deep-when-collecting-relations , by converting a collection to an array before iterating over its members' associations

stack_level.rb

require 'rubygems'

dm_version = "=1.0.2"
gem     "dm-core",        dm_version
require 'dm-core'

gem     "dm-migrations",  dm_version
require 'dm-migrations'

gem     "dm-serializer",  dm_version
require 'dm-serializer'

require 'spec'
require 'spec/autorun'
require 'spec/interop/test'

class Thing
  include DataMapper::Resource
  
  property    :id,             Serial,   :key => true
  
  has n,      :thing_taggings
  has n,      :tags, :through => :thing_taggings
end

class ThingTagging
  include DataMapper::Resource
  
  property    :id,             Serial,   :key => true

  belongs_to  :thing
  belongs_to  :tag
end

class Tag
  include DataMapper::Resource
  
  property    :id,             Serial, :key => true
  property    :title,          String, :length => 128
  
  has n,      :thing_taggings
  has n,      :things, :through => :thing_taggings
end

DataMapper.finalize
DataMapper.setup(:default, "sqlite3://#{Dir.pwd}/test.sqlite3")

describe "Problem" do
  before do
    DataMapper.auto_migrate!
    
    one = Tag.create(:title => "one")
    two = Tag.create(:title => "two")
    three = Tag.create(:title => "three")
    four = Tag.create(:title => "four")
    
    one_two = Thing.create
    one_two.thing_taggings.create(:tag => one)
    one_two.thing_taggings.create(:tag => two)
    
    three_two = Thing.create
    three_two.thing_taggings.create(:tag => three)
    three_two.thing_taggings.create(:tag => two)
    
    three_four = Thing.create
    three_four.thing_taggings.create(:tag => three)
    three_four.thing_taggings.create(:tag => four)
    
    @things = ["three", "four"].map{|tag| Tag.all(:title => tag).things }.reduce{|x, y| x & y }
  end
  it "should collect things" do
    r = {:status => "success", :things => @things}
    r[:things].should have(1).item
  end
  # it "should collect things with relations" do
  #   r = {:status => "success", :things => @things.map{|e| {:tags => e.tags}}}
  #   r[:things].should have(1).item
  #   r[:things].first[:tags].should have(2).items
  # end
  it "will collect things with relations if the collection is converted to an array before" do
    r = {:status => "success", :things => @things.to_a.map{|e| {:tags => e.tags}}}
    r[:things].should have(1).item
    r[:things].first[:tags].should have(2).items
  end
end