invoke (Rake::Task)

         # File lib/rake.rb, line 349
    349:     def invoke
    350:       @lock.synchronize do
    351:         if application.options.trace
    352:           puts "** Invoke #{name} #{format_trace_flags}"
    353:         end
    354:         return if @already_invoked
    355:         @already_invoked = true
    356:         invoke_prerequisites
    357:         execute if needed?
    358:       end
    359:     end