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rubyrake

What is the magic behind "desc 'description'" on rake?

For example on https://github.com/locomotivecms/wagon/blob/master/Rakefile#L23

desc 'build the gem and release it to rubygems.org'
task release: :gem do
  sh "gem push pkg/locomotivecms_wagon-#{gemspec.version}.gem"
end

When i ran rake --task, it returned as description.

rake clobber_package   # Remove package products
rake gem               # Build the gem file locomotivecms_wagon-2.2.0.beta1.gem
rake package           # Build all the packages
rake release           # build the gem and release it to rubygems.org
rake repackage         # Force a rebuild of the package files
rake spec              # Run RSpec code examples
rake spec:integration  # Run RSpec code examples
rake spec:unit         # Run RSpec code examples

But i dont understand how can they take the description, isn't it replaced every time the description called ? How do they know specific description belongs to specific task ?

Solution

  • Imagine simple DSL that has a state (very naïve implementation):

    @tasks = []
@current = nil

def desc text
  @current = Task.new(desc: text)
end

def task params, &cb
  @current.update(params)
  yield
   ....
  @tasks << @current
  @current = nil
end

    The code above requires additional checks etc, but the idea is that: stateful DSL collects tasks with their descriptions.