* check root output values when determining plan applicability in refresh mode
In refresh-only mode, we do not anticipate proposing any actions; however, a plan is marked as “applyable” if there are changes in the state between runs. Currently, a plan is considered “applyable” only when there are differences in managed resources. This approach seems to overlook changes in root output values. As a result, a plan can be marked as non-applyable, even when there are changes in the root output value, due to the lack of detected changes since only managed resources were checked.
* set 'applyable' to true
These ideas are both already implied by some logic elsewhere in the system,
but until now we didn't have the decision logic centralized in a single
place that could therefore evolve over time without necessarily always
updating every caller together.
We'll now have the modules runtime produce its own boolean ruling about
each characteristic, which callers can rely on for the mechanical
decision-making of whether to offer the user an "approve" prompt, and
whether to remind the user after apply that it was an incomplete plan
that will probably therefore need at least one more plan/apply round to
converge.
The "Applyable" flag directly replaces the previous method Plan.CanApply,
with equivalent logic. Making this a field instead of a method means that
we can freeze it as part of a saved plan, rather than recalculating it
when we reload the plan, and we can export the field value in our export
formats like JSON while ensuring it'll always be consistent with what
Terraform is using internally.
Callers can (and should) still use other context in the plan to return
more tailored messages for specific situations they already know about
that might be useful to users, but with these flags as a baseline callers
can now just fall back to a generic presentation when encountering a
situation they don't yet understand, rather than making the wrong decision
and causing something strange to happen. That is: a lack of awareness of
a new rule will now cause just a generic message in the UI, rather than
incorrect behavior.
This commit mostly just deals with populating the flags, and then all of
the direct consequences of that on our various tests. Further changes to
actually make use of these flags elsewhere in the system will follow in
later commits, both in this repository and in other repositories.
Previously the supported JSON plan and state formats included only
serialized output values, which was a lossy serialization of the
Terraform type system. This commit adds a type field in the usual cty
JSON format, which allows reconstitution of the original value.
For example, previously a list(string) and a set(string) containing the
same values were indistinguishable. This change serializes these as
follows:
{
"value": ["a","b","c"],
"type": ["list","string"]
}
and:
{
"value": ["a","b","c"],
"type": ["set","string"]
}
In order to include condition block results in the JSON plan output, we
must store them in the plan and its serialization.
Terraform can evaluate condition blocks multiple times, so we must be
able to update the result. Accordingly, the plan.Conditions object is a
map with keys representing the condition block's address. Condition
blocks are not referenceable in any other context, so this address form
cannot be used anywhere in the configuration.
The commit includes a new test case for the JSON output of a
refresh-only plan, which is currently the only way for a failing
condition result to be rendered through this path.
