Are task dependencies always run in a specific order with rake?

Question

I have the following example which is based on the structure i want my rakefile to use:

task :default do
    puts 'Tasks you can run: dev, stage, prod'
end

task :dev => [:init,:devrun,:clean]
task :devrun do
    puts 'Dev stuff'
end

task :stage => [:init,:stagerun,:clean]
task :stagerun do
    puts 'Staging stuff'
end

task :prod => [:init,:prodrun,:clean]
task :prodrun do
    puts 'Production stuff'
end

task :init do
    puts 'Init...'
end

task :clean do
    puts 'Cleanup'
end

Will the tasks always be run in the same order? I read somewhere that they wouldn't, and somewhere else that they would, so i'm not sure.

Or if you can suggest a better way to do what i'm trying to achieve (eg have a common init and cleanup step surrounding a depending-upon-environment step), that'd also be good.

Thanks

Answer 1

From the Rake source code:

# Invoke all the prerequisites of a task.
def invoke_prerequisites(task_args, invocation_chain) # :nodoc:
  @prerequisites.each { |n|
    prereq = application[n, @scope]
    prereq_args = task_args.new_scope(prereq.arg_names)
    prereq.invoke_with_call_chain(prereq_args, invocation_chain)
  }
end

So it appears that the code normally just iterates the array and runs the prerequisite tasks sequentially.

However:

# Declare a task that performs its prerequisites in parallel. Multitasks does
# *not* guarantee that its prerequisites will execute in any given order
# (which is obvious when you think about it)
#
# Example:
#   multitask :deploy => [:deploy_gem, :deploy_rdoc]
#
def multitask(args, &block)
  Rake::MultiTask.define_task(args, &block)
end

So you are right, both can be true, but order can only be off if you prefix your task with multitask It looks like regular tasks are run in order.