rake_in_30_lines.rb

require "set"

module RakeTask
  CALLED = Set.new
  NAMESPACES = []
  TASKS = Hash.new { |h, k| h[k] = Struct.new(:blocks, :deps).new([], []) }

  class << self
    def call(name)
      return if CALLED.include?(name)
      raise "Unknown task: #{name.inspect}" unless TASKS.key?(name)

      CALLED << name
      (task = TASKS[name]).deps.each { |t| call(t) }
      task.blocks.each { |b| b[] }
    end

    def namespace(name, &block)
      NAMESPACES << name && yield ensure NAMESPACES.pop!
    end
    
    def task(spec, &block)
      name, deps = spec.entries[0] rescue name = spec
      name, deps = (NAMESPACES + [name.to_s]) * ":", Array(deps).map { |d| d.to_s }
    
      TASKS[name].blocks << block
      TASKS[name].deps |= deps
    end
  end
end

RakeTask.module_eval do
  task :super do
    puts "Super"
  end
  
  task :super do
    puts "Super2"
  end
  
  task "duper" do
    puts "Duper"
  end
  
  task :awesome => :super do
    puts "Awesome"
  end
  
  task :cool => [:awesome, :duper] do
    puts "Cool"
  end
  
  %w(awesome cool).each { |t| RakeTask.call(t) }
end