Wednesday, June 3, 2009

Renaming a Rake task

Rake has a class for creating packaging task which builds a compressed package from the sources. It's called Rake::PackageTask and it's quite easy to use it, see the documentation.

Unfortunately the name of the created task is package and it's hardcoded so it cannot be changed.
Yast uses make and the standard targets are package and package-local.

  • package-local - build a tarball source package
  • package - does some checks (like SVN repository update check, syntax check, runs the testsuite...) to ensure that the built package follows some rules so it will less likely break something.

We wanted to use the same targets in the Web Yast which uses Ruby on Rails and Rake as the make replacement.

The problem is how to change the package task name. In Ruby it's possible to change or extend even the core classes like String or Object, which might be good or bad because you can break all Ruby applications very easily... But this feature allow us to extend Rake as we need.

The following code adds rename method to Rake::Task class:

# add rename_task method to Rake::Application
# it has an internal hash with name -> Rake::Task mapping
module Rake
class Application
def rename_task(task, oldname, newname)
if @tasks.nil?
@tasks = {}

@tasks[newname.to_s] = task

if @tasks.has_key? oldname
@tasks.delete oldname

# add new rename method to Rake::Task class
# to rename a task
class Rake::Task
def rename(new_name)
if !new_name.nil?
old_name = @name

if old_name == new_name

@name = new_name.to_s
application.rename_task(self, old_name, new_name)

And an example how to use it:

# rename 'package' task to 'package-local' task

It was quite difficult to figure out the rake internals, so I hope it will help somebody else...

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