module Rake::TaskManager

def attempt_rule(task_name, extensions, block, level)
  sources = make_sources(task_name, extensions)
  prereqs = sources.collect { |source|
    trace_rule level, "Attempting Rule #{task_name} => #{source}"
    if File.exist?(source) || Rake::Task.task_defined?(source)
      trace_rule level, "(#{task_name} => #{source} ... EXIST)"
      source
    elsif parent = enhance_with_matching_rule(source, level+1)
      trace_rule level, "(#{task_name} => #{source} ... ENHANCE)"
      parent.name
    else
      trace_rule level, "(#{task_name} => #{source} ... FAIL)"
      return nil
    end
  }
  task = FileTask.define_task({task_name => prereqs}, &block)
  task.sources = prereqs
  task
end