Default task for namespace in Rake

Place it outside the namespace like this:

namespace :my_tasks do
  task :foo do
    do_something
  end

  task :bar do
    do_something_else
  end

end

task :all => ["my_tasks:foo", "my_tasks:bar"]

Also... if your tasks require arguments then:

namespace :my_tasks do
  task :foo, :arg1, :arg2 do |t, args|
    do_something
  end

  task :bar, :arg1, :arg2  do |t, args|
    do_something_else
  end

end

task :my_tasks, :arg1, :arg2 do |t, args|
  Rake::Task["my_tasks:foo"].invoke( args.arg1, args.arg2 )
  Rake::Task["my_tasks:bar"].invoke( args.arg1, args.arg2 )
end

Notice how in the 2nd example you can call the task the same name as the namespace, ie 'my_tasks'

Not very intuitive, but you can have a namespace and a task that have the same name, and that effectively gives you what you want. For instance

namespace :my_task do
  task :foo do
    do_foo
  end
  task :bar do
    do_bar
  end
end

task :my_task do
  Rake::Task['my_task:foo'].invoke
  Rake::Task['my_task:bar'].invoke
end

Now you can run commands like,

rake my_task:foo

and

rake my_task