Notifications in Custom Chef Resources
After some hair pulling, I realized that it was a Custom Provider, and more specifically, a Custom Lightweight Resource (LWRP).
As it turns out, if you actually RTFM, then you’ll find this little nugget:
To ensure that an embedded lightweight resource can notify the top-level resource add use_inline_resources to the top of the file that defines the lightweight provider that is associated with that lightweight resource.
As such, I modified my provider thusly:
action :create do