This means it’s shown correctly in a plan and takes into account any
actions that are dependant on the tainted resource and, vice verse, any
actions that the tainted resource depends on.
So this changes the behaviour from saying this resource is tainted so
just forget about it and make sure it gets deleted in the background,
to saying I want that resource to be recreated (taking into account the
existing resource and it’s place in the graph).
Because CBD now runs after a RootTransformer, it's now operating on a
graph that _may_ have had a graphNodeRoot added to it (a noop node whose
only purpose is to be a root).
CBD includes a step that tells the destroy node to depend on any parents
of the create node. When one of those parents was "root", this was
causing the destroy node to depend on "root", making it cease to be an
actual root node.
Because graphNodeRoot is a singleton, the follow-up RootTransformer was
not sufficient to slap another root on top - it wasn't being seen as a
fresh node, so edges were just accumulating, and we ended up in a state
with "no roots".
refs #1903 (not sure if this will fix all the "no root found" cases, or
just the one I bumped into)
Sander van Harmelen