Our previous rule for implicitly moving from IntKey(0) to NoKey would
apply that move even when the current resource configuration uses
for_each, because we were only considering whether "count" were set.
Previously this was relatively harmless because the resource instance in
question would end up planned for deletion anyway: neither an IntKey nor
a NoKey are valid keys for for_each.
Now that we're going to be announcing these moves explicitly in the UI,
it would be confusing to see Terraform report that IntKey moved to NoKey
in a situation where the config changed from count to for_each, so to
address that we'll only generate the implied statement if neither
repetition argument is set.
This new function complements the existing function FindMoveStatements
by potentially generating additional "implied" move statements that aren't
written explicit in the configuration but that we'll infer by comparing
the configuration and te previous run state.
The goal here is to infer only enough to replicate the effect of the
"count boundary fixup" graph node (terraform.NodeCountBoundary) that we
currently use to deal with this concern of preserving the zero-instance
when switching between "count" and not "count".
This is just dead code for now. A subsequent commit will introduce this
into the "terraform" package while also removing
terraform.NodeCountBoundary, thus achieving the same effect as before but
in a way that'll get reported in the UI as a move, using the same language
that we'd use for an explicit move statement.
This is a whole lot of nothing right now, just stubbing out some control
flow that ultimately just leads to TODOs that cause it to do nothing at
all.
My intent here is to get this cross-cutting skeleton in place and thus
make it easier for us to collaborate on adding the meat to it, so that
it's more likely we can work on different parts separately and still get
a result that tessellates.
We previously built out addrs.UnifyMoveEndpoints with a different
implementation strategy in mind, but that design turns out to not be
viable because it forces us to move to AbsMoveable addresses too soon,
before we've done the analysis required to identify chained and nested
moves.
Instead, UnifyMoveEndpoints will return a new type MoveEndpointInModule
which conceptually represents a matching pattern which either matches or
doesn't match a particular AbsMoveable. It does this by just binding the
unified relative address from the MoveEndpoint to the module where it
was declared, and thus allows us to distinguish between the part of the
module path which applies to any instances of the given modules vs. the
user-specified part which must identify particular module instances.
