Check if rake task exists from within Rakefile

I'm looking for a way to be able to check if a certain rake task exists from within the Rakefile. I have a task dependency that I only want to include as a dependency if that task is available. In this particular case, the task is only available in a Rails project, but I want my rake tasks to work in a more general Ruby application environment too (not just Rails).

I want to do something like this:

if tasks.includes?('assets:precompile')
  task :archive => [:clean, :vendor_deps, 'assets:precompile']
    ...
  end
else
  task :archive => [:clean, :vendor_deps]
    ...
  end
end

What is the best way to conditionally include a task dependency in a rake task?

Solution

what about doing something like this? Invoke the task if it exists, as opposed to making it an explicit dependency?

 task :archive => [:clean, :vendor_deps] do 
  Rake.application["assets:precompile"].invoke if Rake::Task.task_defined?('assets:precompile')
   .... 
  end

or even easier. Since specifying the task again allows you to add to it, something like this appears to work as well.

task :archive => [:clean, :vendor_deps] do
    ...
  end
task :archive => "assets:precompile" if  Rake::Task.task_defined?("assets:precompile")

which will conditionally add the dependency on assets:precompile if it is defined.