Going back a long time we've had a special magic behavior which tries to
recognize a situation where a module author either added or removed the
"count" argument from a resource that already has instances, and to
silently rename the zeroth or no-key instance so that we don't plan to
destroy and recreate the associated object.
Now we have a more general idea of "move statements", and specifically
the idea of "implied" move statements which replicates the same heuristic
we used to use for this behavior, we can treat this magic renaming rule as
just another "move statement", special only in that Terraform generates it
automatically rather than it being written out explicitly in the
configuration.
In return for wiring that in, we can now remove altogether the
NodeCountBoundary graph node type and its associated graph transformer,
CountBoundaryTransformer. We handle moves as a preprocessing step before
building the plan graph, so we no longer need to include any special nodes
in the graph to deal with that situation.
The test updates here are mainly for the graph builders themselves, to
acknowledge that indeed we're no longer inserting the NodeCountBoundary
vertices. The vertices that NodeCountBoundary previously depended on now
become dependencies of the special "root" vertex, although in many cases
here we don't see that explicitly because of the transitive reduction
algorithm, which notices when there's already an equivalent indirect
dependency chain and removes the redundant edge.
We already have plenty of test coverage for these "count boundary" cases
in the context tests whose names start with TestContext2Plan_count and
TestContext2Apply_resourceCount, all of which continued to pass here
without any modification and so are not visible in the diff. The test
functions particularly relevant to this situation are:
- TestContext2Plan_countIncreaseFromNotSet
- TestContext2Plan_countDecreaseToOne
- TestContext2Plan_countOneIndex
- TestContext2Apply_countDecreaseToOneCorrupted
The last of those in particular deals with the situation where we have
both a no-key instance _and_ a zero-key instance in the prior state, which
is interesting here because to exercises an intentional interaction
between refactoring.ImpliedMoveStatements and refactoring.ApplyMoves,
where we intentionally generate an implied move statement that produces
a collision and then expect ApplyMoves to deal with it in the same way as
it would deal with all other collisions, and thus ensure we handle both
the explicit and implied collisions in the same way.
This does affect some UI-level tests, because a nice side-effect of this
new treatment of this old feature is that we can now report explicitly
in the UI that we're assigning new addresses to these objects, whereas
before we just said nothing and hoped the user would just guess what had
happened and why they therefore weren't seeing a diff.
The backend/local plan tests actually had a pre-existing bug where they
were using a state with a different instance key than the config called
for but getting away with it because we'd previously silently fix it up.
That's still fixed up, but now done with an explicit mention in the UI
and so I made the state consistent with the configuration here so that the
tests would be able to recognize _real_ differences where present, as
opposed to the errant difference caused by that inconsistency.
Previously terraform.Context was built in an unfortunate way where all of
the data was provided up front in terraform.NewContext and then mutated
directly by subsequent operations. That made the data flow hard to follow,
commonly leading to bugs, and also meant that we were forced to take
various actions too early in terraform.NewContext, rather than waiting
until a more appropriate time during an operation.
This (enormous) commit changes terraform.Context so that its fields are
broadly just unchanging data about the execution context (current
workspace name, available plugins, etc) whereas the main data Terraform
works with arrives via individual method arguments and is returned in
return values.
Specifically, this means that terraform.Context no longer "has-a" config,
state, and "planned changes", instead holding on to those only temporarily
during an operation. The caller is responsible for propagating the outcome
of one step into the next step so that the data flow between operations is
actually visible.
However, since that's a change to the main entry points in the "terraform"
package, this commit also touches every file in the codebase which
interacted with those APIs. Most of the noise here is in updating tests
to take the same actions using the new API style, but this also affects
the main-code callers in the backends and in the command package.
My goal here was to refactor without changing observable behavior, but in
practice there are a couple externally-visible behavior variations here
that seemed okay in service of the broader goal:
- The "terraform graph" command is no longer hooked directly into the
core graph builders, because that's no longer part of the public API.
However, I did include a couple new Context functions whose contract
is to produce a UI-oriented graph, and _for now_ those continue to
return the physical graph we use for those operations. There's no
exported API for generating the "validate" and "eval" graphs, because
neither is particularly interesting in its own right, and so
"terraform graph" no longer supports those graph types.
- terraform.NewContext no longer has the responsibility for collecting
all of the provider schemas up front. Instead, we wait until we need
them. However, that means that some of our error messages now have a
slightly different shape due to unwinding through a differently-shaped
call stack. As of this commit we also end up reloading the schemas
multiple times in some cases, which is functionally acceptable but
likely represents a performance regression. I intend to rework this to
use caching, but I'm saving that for a later commit because this one is
big enough already.
The proximal reason for this change is to resolve the chicken/egg problem
whereby there was previously no single point where we could apply "moved"
statements to the previous run state before creating a plan. With this
change in place, we can now do that as part of Context.Plan, prior to
forking the input state into the three separate state artifacts we use
during planning.
However, this is at least the third project in a row where the previous
API design led to piling more functionality into terraform.NewContext and
then working around the incorrect order of operations that produces, so
I intend that by paying the cost/risk of this large diff now we can in
turn reduce the cost/risk of future projects that relate to our main
workflow actions.
This includes the addition of the new "//go:build" comment form in addition
to the legacy "// +build" notation, as produced by gofmt to ensure
consistent behavior between Go versions. The new directives are all
equivalent to what was present before, so there's no change in behavior.
Go 1.17 continues to use the Unicode 13 tables as in Go 1.16, so this
upgrade does not require also upgrading our Unicode-related dependencies.
This upgrade includes the following breaking changes which will also
appear as breaking changes for Terraform users, but that are consistent
with the Terraform v1.0 compatibility promises.
- On MacOS, Terraform now requires macOS 10.13 High Sierra or later.
This upgrade also includes the following breaking changes which will
appear as breaking changes for Terraform users that are inconsistent with
our compatibility promises, but have justified exceptions as follows:
- cidrsubnet, cidrhost, and cidrnetmask will now reject IPv4 CIDR
addresses whose decimal components have leading zeros, where previously
they would just silently ignore those leading zeros.
This is a security-motivated exception to our compatibility promises,
because some external systems interpret zero-prefixed octets as octal
numbers rather than decimal, and thus the previous lenient parsing could
lead to a different interpretation of the address between systems, and
thus potentially allow bypassing policy when configuring firewall rules
etc.
This upgrade also includes the following breaking changes which could
_potentially_ appear as breaking changes for Terraform users, but that do
not in practice for the reasons given:
- The Go net/url package no longer allows query strings with pairs
separated by semicolons instead of ampersands. This primarily affects
HTTP servers written in Go, and Terraform includes a special temporary
HTTP server as part of its implementation of OAuth for "terraform login",
but that server only needs to accept URLs created by Terraform itself
and Terraform does not generate any URLs that would be rejected.
* states: add MoveAbsResource and MoveAbsResourceInstance state functions and corresponding syncState wrapper functions.
* states: add MoveModuleInstance and MaybeMoveModuleInstance
* addrs: adding a new function, ModuleInstance.IsDeclaredByCall, which returns true if the receiver is an instance of the given AbsModuleCall.
This is part of a general effort to move all of Terraform's non-library
package surface under internal in order to reinforce that these are for
internal use within Terraform only.
If you were previously importing packages under this prefix into an
external codebase, you could pin to an earlier release tag as an interim
solution until you've make a plan to achieve the same functionality some
other way.
Martin Atkins