How to do conditional include_recipe (how to use guards with include_recipe)

Lets say you want to include a recipe based on some state of the server. Obviously this is a server you inherited from some team, and rebuilding it is just not an option because server provisioning takes 2 weeks (or two months).

include_recipe "foo::bar" do 
  not_if {
  ::File.exists?("/etc/foo/bar")
  }
end


/\ That simple does't work, although it'd be awesome if it did (seems like a consistency thing to me). Reason for that is include_recipe is a method and not a resource. Which means it's evaluated at the compilation phase, and not at execution (which makes sense from building the resource collection perspective)


So, if you do want a conditional include_recipe, you want to do something like this instead:





some_variable =  {some logic to check for some state on a system} 

include_recide 'foo::bar' unless some_variable





Situation where this becomes super useful for example, is on windows, for chef runs which need to reboot a server and go on:



include_recipe 'cookbook::recipe' unless reboot_pending? 

Great link:

http://stackoverflow.com/questions/15961496/is-it-possible-to-chef-include-recipe-and-indicate-only-if-not-if-condition



The bug I filed on the issue and the resulting discussion:

https://tickets.opscode.com/browse/CHEF-5342

Toodles/