In an earlier commit we changed the states.CheckResults model to
explicitly model the config object vs. dynamic checkable object hierarchy,
but neglected to update the logic in Terraform Core to take that into
account when propagating the object expansion decisions from the plan
phase to the apply phase. That meant that we were incorrectly classifying
zero-instance resources always as having an unknown number of instances,
rather than possibly being known to have zero instances.
This now follows the two-level heirarchy of the data structure, which has
the nice side-effect that we can remove some of the special-case methods
from checks.State that we were using to bulk-load data: the data is now
shaped in the appropriate way to reload the data using the same method
the plan phase would've used to record the results in the first place.
A significant goal of the design changes around checks in earlier commits
(with the introduction of package "checks") was to allow us to
differentiate between a configuration object that we didn't expand at all
due to an upstream error, which has _unknown_ check status, and a
configuration object that expanded to zero dynamic objects, which
therefore has a _passing_ check status.
However, our initial lowering of checks.State into states.CheckResults
stayed with the older model of just recording each leaf check in isolation,
without any tracking of the containers.
This commit therefore lightly reworks our representation of check results
in the state and plan with two main goals:
- The results are grouped by the static configuration object they came
from, and we capture an aggregate status for each of those so that
we can differentiate an unknown aggregate result from a passing
aggregate result which has zero dynamic associated objects.
- The granularity of results is whole checkable objects rather than
individual checks, because checkable objects have durable addresses
between runs, but individual checks for an object are more of a
syntactic convenience to make it easier for module authors to declare
many independent conditions that each have their own error messages.
Since v1.2 exposed some details of our checks model into the JSON plan
output there are some unanswered questions here about how we can shift to
reporting in the two-level heirarchy described above. For now I've
preserved structural compatibility but not semantic compatibility: any
parser that was written against that format should still function but will
now see fewer results. We'll revisit this in a later commit and consider
other structures and what to do about our compatibility constraint on the
v1.2 structure.
Otherwise though, this is an internal-only change which preserves all of
the existing main behaviors of conditions as before, and just gets us
ready to build user-facing features in terms of this new structure.
The "checks" package is an expansion what we previously called
plans.Conditions to accommodate a new requirement that we be able to track
which checks we're expecting to run even if we don't actually get around
to running them, which will be helpful when we start using checks as part
of our module testing story because test reporting tools appreciate there
being a relatively consistent set of test cases from one run to the next.
So far this should be essentially a no-op change from an external
functionality standpoint, aside from some minor adjustments to how we
report some of the error and warning cases from condition evaluation in
light of the fact that the "checks" package can now track errors as a
different outcome than a failure of a valid check.
As is often the case with anything which changes what we track
in the EvalContext and persist between plan and apply, Terraform Core is
pretty brittle and so this had knock-on effects elsewhere too. Again, the
goal is for these changes to not create any material externally-visible
difference, and just to accommodate the new assumption that there will
always be a "checks" object available for tracking during a graph walk.
