Add a transitive test property

[ekohl]

This is a minimal reproducer that's essentially A ~> B ~> C. The that_subscribes_to matcher shows that this is equal to A ~> C but in practice Puppet doesn't work that way. The service is not restarted if the file is modified.

I don't know what is the expected behavior here, but it does mean that today it's not possible to test for real world behavior.

I've submitted this as a PR since it's the easiest way to submit code and show CI results for it.

[sanfrancrisko]

Thanks for highlighting this @ekohl. Let me run this past a few colleagues, but it would seem logical that the test framework is behaving the same way as Puppet behaves, at least. However, we can start a separate conversation with the Puppet core team if you feel there's an issue with how chained notifies are working at the moment?

[ekohl]

I would like a formal statement from the core team how they think it should work. From there we can decide how to approach this.

[sanfrancrisko]

I pinged some of my colleagues from the agent team and they believe that A should notify both B and C (C being triggered by B) in the case outlined in https://github.com/theforeman/puppet-foreman_proxy/pull/653. I'll relay your manifest here to them and see if I can reproduce it too. If so, we'll get a bug raised as it seems to be contradicting the expected behaviour: https://puppet.com/docs/puppet/7.6/lang_relationships.html#lang_rel_chaining_arrows

[ekohl]

It is my impression that it relies on some resource triggering the notify. So if you have:

Class['A'] ~> Class['B'] ~> Class['C']

Then it works if there's a resource inside Class['B'] that triggers a refresh. However, we've seen the edge case where it wasn't. Perhaps classes also behave different than resources.

[evgeni]

@sanfrancrisko was there ever any progress on this discussion? We've just hit this problem again and while re-reading https://puppet.com/docs/puppet/7/lang_relationships.html#lang_rel_chaining_arrows I can't really tell if A ~> B ~> C should be equivalent to A ~> B, A ~> C, B ~> C or A ~> B, B ~> C?

More explicitly, the chaining example says "Resource declarations can be chained. That means you can use chaining arrows to make Puppet apply a section of code in the order that it is written. This example applies configuration to the package, the file, and the service, in that order, with each related resource notifying the next of any changes" (emph. mine) where one could interpret "any changes" as "any changes to itself" and not "any changes in the whole chain".

[ekohl]

Please continue the discussion in https://github.com/puppetlabs/rspec-puppet/pull/29