Jira (PUP-10417) Custom Ruby functions that define a JSON module can ambiguate its scope and break Puppet

Justin Stoller (Jira) Thu, 09 Apr 2020 12:28:07 -0700

Title: Message Title

I looked into this a little bit today and:

I looked into changing how we do that eval and I'm very hesitant to change bindings w/o a lot more leg work, and probably not on anything but a major version boundary.

Their "workaround" of "Don't monkey patch JSON" is less a dirty hack and more a best practice.

Considering how the implementation of function loading was implemented, I think the assumption was that users would not be defining custom modules in their function files. The alternative would be to do what is recommended for library code w/in types and providers. I didn't see this recommendation on our docs but something like the "Shared Libraries" section of the old https://www.oreilly.com/library/view/puppet-types-and/9781449339319/ch04.html. (The weird "File.expand_path"s can be removed for a more modern "require_relative").

So I think we should document something to the effect of:

If you want to factor out helper functions within your 4x style Ruby based Puppet functions you can define those inside the block given to Puppet::Functions.create_function. If you'd like to break those helper functions out to be easily unit testable, share them with other functions, or group them logically into a Ruby Module, you should define them in a namespaced helper file, and require that file within the body of the block you pass to Puppet::Functions.create_function. eg in some Ruby-ish pseudo code:

# cat mymodule/lib/puppet/functions/mymodule/foo.rb

Puppet::Functions.create_function("mymodule::foo") do

  require_relative "../../../puppet_x/my_org/my_module/helpers.rb

  dispatch "foo" do

    ...not pertinent...

end

  def foo(args)

    PuppetX::MyOrg::MyModule::Helpers.do_a_thing(args)

end

end

# cat mymodule/lib/puppet_x/my_org/my_module/helpers.rb

require 'your/hearts/content'

module PuppetX

  module MyOrg

    module MyModule

      module Helpers

        def self.do_a_thing(args)

          ...namespaced to not interfere with puppet & unit testable without requiring puppet!

end

end

end

end

end

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Jira (PUP-10417) Custom Ruby functions that define a JSON module can ambiguate its scope and break Puppet

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