We need to be able to reference all possible dependencies for ordering
when the configuration is no longer present, which means that absolute
addresses must be used. Since this is only to recreate the proper
ordering for instance destruction, only resources addresses need to be
listed rather than individual instance addresses.
The fallback type for GetResource from an EachMap is a cty.Object,
because resource schemas may contain dynamically typed attributes.
Check for an Object type in the evaluation of self, to use the proper
GetAttr method when extracting the value.
These are often confusing for new contributors, since this looks
suspiciously like the right place to add new functions or change the
behavior of existing ones.
To reduce that confusion, here we remove them entirely from this package
(which is now dead code in Terraform 0.12 anyway) and include in the
documentation comments a pointer to the current function implementations.
If a resource is only destroying instances, there is no reason to
prepare the state and we can remove the Resource (prepare state) nodes.
They normally have pose no issue, but if the instances are being
destroyed along with their dependencies, the resource node may fail to
evaluate due to the missing dependencies (since destroy happens in the
reverse order).
These failures were previously blocked by there being a cycle when the
destroy nodes were directly attached to the resource nodes.
Destroy nodes do not need to be connected to the resource (prepare
state) node when adding them to the graph. Destroy nodes already have a
complete state in the graph (which is being destroyed), any references
will be added in the ReferenceTransformer, and the proper
connection to the create node will be added in the
DestroyEdgeTransformer.
Under normal circumstances this makes no difference, as create and
destroy nodes always have an dependency, so having the prepare state
handled before both only linearizes the operation slightly in the
normal destroy-then-create scenario.
However if there is a dependency on a resource being replaced in another
module, there will be a dependency between the destroy nodes in each
module (to complete the destroy ordering), while the resource node will
depend on the variable->output->resource chain. If both the destroy and
create nodes depend on the resource node, there will be a cycle.
The CBDEdgeTransformer tests worked on fake data structures, with a
synthetic graph, and configs that didn't match. Update them to generate
a more complete graph, with real node implementations, from real
configs.
The output graph is filtered down to instances, and the results still
functionally match the original expected test results, with some minor
additions due to using the real implementation.
When looking for dependencies to fix when handling
create_before_destroy, we need to look past more than one edge, as
dependencies may appear transitively through outputs and variables. Use
Descendants rather than UpEdges.
We have the full graph to use for the CBD transformation, so there's no
longer any need to create a temporary graph, which may differ from the
original.
Martin Atkins