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 the graph builders all expected to be given a full manifest
of all of the plugin component schemas that they could need during their
analysis work. That made sense when terraform.NewContext would always
proactively load all of the schemas before doing any other work, but we
now have a load-as-needed strategy for schemas.
We'll now have the graph builders use the contextPlugins object they each
already hold to retrieve individual schemas when needed. This avoids the
need to prepare a redundant data structure to pass alongside the
contextPlugins object, and leans on the memoization behavior inside
contextPlugins to preserve the old behavior of loading each provider's
schema only once.
In the v0.12 timeframe we made contextComponentFactory an interface with
the expectation that we'd write mocks of it for tests, but in practice we
ended up just always using the same "basicComponentFactory" implementation
throughout.
In the interests of simplification then, here we replace that interface
and its sole implementation with a new concrete struct type
contextPlugins.
Along with the general benefit that this removes an unneeded indirection,
this also means that we can add additional methods to the struct type
without the usual restriction that interface types prefer to be small.
In particular, in a future commit I'm planning to add methods for loading
provider and provisioner schemas, working with the currently-unused new
fields this commit has included in contextPlugins, as compared to its
predecessor basicComponentFactory.
In earlier incarnations of these transformers we used the set of all
available providers for tasks such as generating implied provider
configuration nodes.
However, in modern Terraform we can extract all of the information we need
from the configuration itself, and so these transformers weren't actually
using this set of provider addresses.
These also ended up getting left behind as sets of string rather than sets
of addrs.Provider in our earlier refactoring work, which didn't really
matter because the result wasn't used anywhere anyway.
Rather than updating these to use addrs.Provider instead, I've just
removed the unused arguments entirely in the hope of making it easier to
see what inputs these transformers use to make their decisions.
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.
