Rudder

Please note, that https://www.rudder-project.org/doc-4.2/_directives_ordering.html is in fact incomplete.

https://www.mauras.ch/rudder-fun-with-variables.html
is exploiting undocumented fact that "Priority" field takes precedence over alpha-numeric naming order.
It's really useful together with generic_variable_definition, allowing us to make multilevel overriding (like Chef does).

It works because vars in generic_variable_definition are just internal objects, and redeclaration is ok in cfengine.

Example:

bundle common generic_variable_definition
{

  vars:
    "SECURITY_ACCESS_CONF" string => "admins",
            policy => "overridable";

…
    "SECURITY_ACCESS_CONF" string => "admins,etc",
            policy => "overridable";
…

will set generic_variable_definition.SECURITY_ACCESS_CONF = "admins,etc".

Just use another directive with higher "Priority" (0>1>…>10). And last one will be used.

• M.b. it works with other directives, but (in general) is useless in management of external objects.
  Per contra, it's very useful to override internal declarations, providing scalar priority instead of 2-level name-sorting hell.

It's also a good workaround against single-level group hierarchy.