Rails SQL sanitizing and Ruleby

I ran into an issue when using Rails with conditional associations and Ruleby. Some background, I have two models, a Store and a Batch. Store has many batches, and has one current batch, which is simply a conditional association where the batch has a state of "open."

Here's my stack trace when I try to access the current_batch association.

ruby-1.9.2-p290 :002 > Store.first.current_batch
SyntaxError: (eval):1: syntax error, unexpected tSTRING_BEG
Proc.new { || "batches"."workflow_state" = 'open' }
                         ^
(eval):1: syntax error, unexpected '=', expecting '}'
Proc.new { || "batches"."workflow_state" = 'open' }
                                          ^
  from gems/ruleby-0.8/lib/ruleby.rb:55:in `eval'
  from gems/ruleby-0.8/lib/ruleby.rb:55:in `to_proc'
  from gems/activerecord-3.0.9/lib/active_record/base.rb:1753:in `interpolate_sanitized_sql'
  from gems/activerecord-3.0.9/lib/active_record/associations/association_proxy.rb:165:in `interpolate_sanitized_sql'
  from gems/activerecord-3.0.9/lib/active_record/associations/association_proxy.rb:105:in `conditions'
  from gems/activerecord-3.0.9/lib/active_record/associations/has_one_association.rb:102:in `construct_sql'
  from gems/activerecord-3.0.9/lib/active_record/associations/has_one_association.rb:7:in `initialize'
  from gems/activerecord-3.0.9/lib/active_record/associations.rb:1441:in `new'
  from gems/activerecord-3.0.9/lib/active_record/associations.rb:1441:in `block in association_accessor_methods'
  from (irb):2
  from gems/railties-3.0.9/lib/rails/commands/console.rb:44:in `start'
  from gems/railties-3.0.9/lib/rails/commands/console.rb:8:in `start'
  from gems/railties-3.0.9/lib/rails/commands.rb:23:in `<top (required)>'
  from script/rails:6:in `require'
  from script/rails:6:in `<main>'

Rails does some magic on the arguments it gets passed when defining a conditional association, here's the code I believe is causing issues with Ruleby.

def interpolate_sanitized_sql(sanitized, record = nil, sanitize_klass = self.class)
  if sanitized =~ /\#\{.*\}/
    ActiveSupport::Deprecation.warn(
      'String-based interpolation of association conditions is deprecated. Please use a ' \
      'proc instead. So, for example, has_many :older_friends, :conditions => \'age > #{age}\' ' \
      'should be changed to has_many :older_friends, :conditions => proc { "age > #{age}" }.'
    )
    instance_eval("%@#{sanitized.gsub('@', '\@')}@", __FILE__, __LINE__)
  elsif sanitized.respond_to?(:to_proc)
    sanitize_klass.send(:sanitize_sql, instance_exec(record, &sanitized))
  else
    sanitized
  end
end

It asks the object being passed in if it responds to #to_proc. Under normal circumstances, String would not respond to #to_proc so there would be nothing happening here and it would just return the generated and sanitized SQL. But, since Ruleby provides a String#to_proc method, Rails runs the proc and Ruleby just gets really confused at the String it's working with.

I'm still working on a workaround/patch, but I wanted to see if anyone here had any ideas. I'll update this with my findings.

Ruleby / ruleby

Rails SQL sanitizing and Ruleby #19