I missed this on my first attempt to write this document. Consequently
we're currently depending on a version of HCL which uses Unicode 9, and
that's significantly lagging behind everything else which is currently on
Unicode 13.
My goal of adding these docs then is to remind us to update HCL to Unicode
15 once we're updating everything else to Unicode 15 with the Go 1.20
release, assuming that the Go team completes that Unicode upgrade as
currently planned.
Some prior refactors left the detroyPlan method a bit confusing, and ran
into a case where the previous run state could be returned as nil.
Get rid of the no longer used pendingPlan value, and track the prior and
prev states directly, making sure we always have a value for both.
In order to complete the terraform destroy command, a refresh must first
be done to update state and remove any instances which have already been
deleted externally. This was being done with a refresh plan, which will
avoid any condition evaluations and avoid planning new instances. That
however can fail due to invalid references from resources that are
already missing from the state.
A new plan type to handle the concept of the pre-destroy-refresh is
needed here, which should probably be incorporated directly into the
destroy plan, just like the original refresh walk was incorporated into
the normal planning process. That however is major refactoring that is
not appropriate for a patch release.
Instead we make two discrete changes here to prevent blocking a destroy
plan. The first is to use a normal plan to refresh, which will enable
evaluation because missing and inconsistent instances will be planned
for creation and updates, allowing them to be evaluated. That is not
optimal of course, but does revert to the method used by previous
Terraform releases until a better method can be implemented.
The second change is adding a preDestroyRefresh flag to the planning
process. This is checked in any location which evalCheckRules is called,
and lets us change the diagnosticSeverity of the output to only be
warnings, matching the behavior of a normal refresh plan.
When we originally introduced the trust-on-first-use checksum locking
mechanism in v0.14, we had to make some tricky decisions about how it
should interact with the pre-existing optional read-through global cache
of provider packages:
The global cache essentially conflicts with the checksum locking because
if the needed provider is already in the cache then Terraform skips
installing the provider from upstream and therefore misses the opportunity
to capture the signed checksums published by the provider developer. We
can't use the signed checksums to verify a cache entry because the origin
registry protocol is still using the legacy ziphash scheme and that is
only usable for the original zipped provider packages and not for the
unpacked-layout cache directory. Therefore we decided to prioritize the
existing cache directory behavior at the expense of the lock file behavior,
making Terraform produce an incomplete lock file in that case.
Now that we've had some real-world experience with the lock file mechanism,
we can see that the chosen compromise was not ideal because it causes
"terraform init" to behave significantly differently in its lock file
update behavior depending on whether or not a particular provider is
already cached. By robbing Terraform of its opportunity to fetch the
official checksums, Terraform must generate a lock file that is inherently
non-portable, which is problematic for any team which works with the same
Terraform configuration on multiple different platforms.
This change addresses that problem by essentially flipping the decision so
that we'll prioritize the lock file behavior over the provider cache
behavior. Now a global cache entry is eligible for use if and only if the
lock file already contains a checksum that matches the cache entry. This
means that the first time a particular configuration sees a new provider
it will always be fetched from the configured installation source
(typically the origin registry) and record the checksums from that source.
On subsequent installs of the same provider version already locked,
Terraform will then consider the cache entry to be eligible and skip
re-downloading the same package.
This intentionally makes the global cache mechanism subordinate to the
lock file mechanism: the lock file must be populated in order for the
global cache to be effective. For those who have many separate
configurations which all refer to the same provider version, they will
need to re-download the provider once for each configuration in order to
gather the information needed to populate the lock file, whereas before
they would have only downloaded it for the _first_ configuration using
that provider.
This should therefore remove the most significant cause of folks ending
up with incomplete lock files that don't work for colleagues using other
platforms, and the expense of bypassing the cache for the first use of
each new package with each new configuration. This tradeoff seems
reasonable because otherwise such users would inevitably need to run
"terraform providers lock" separately anyway, and that command _always_
bypasses the cache. Although this change does decrease the hit rate of the
cache, if we subtract the never-cached downloads caused by
"terraform providers lock" then this is a net benefit overall, and does
the right thing by default without the need to run a separate command.
* Convert variable types before applying defaults
* revert change to unrelated test
* Add another test case to verify behaviour
* update go-cty
* Update internal/terraform/eval_variable.go
Co-authored-by: alisdair <alisdair@users.noreply.github.com>
Co-authored-by: alisdair <alisdair@users.noreply.github.com>
We need to avoid re-writing the state for every NoOp apply. We may
still be evaluating the instance to account for any side-effects in the
condition checks, however the state of the instance has not changes.
Re-writing the state is a non-current operation, which may require
encoding a fairly large instance state and re-serializing the entire
state blob, so it is best avoided if possible.
Ensure that empty check results are normalized in state serialization to
prevent unexpected state changes from being written.
Because there is no consistent empty, null and omit_empty usage for
state structs, there's no good way to create a test which will fail
for future additions.
If there are no changes, then there is no reason to create an apply
graph since all objects are known. We however do need the walk to match
the expected state structure. This is probably only cleanup of empty
nested modules and outputs, but some investigation is needed before
making the full change.
For now we can store the checks from the plan directly into the new
state, since the apply walk overwrote the results we had already.
