Due to how often the state and plan types are referenced throughout
Terraform, there isn't a great way to switch them out gradually. As a
consequence, this huge commit gets us from the old world to a _compilable_
new world, but still has a large number of known test failures due to
key functionality being stubbed out.
The stubs here are for anything that interacts with providers, since we
now need to do the follow-up work to similarly replace the old
terraform.ResourceProvider interface with its replacement in the new
"providers" package. That work, along with work to fix the remaining
failing tests, will follow in subsequent commits.
The aim here was to replace all references to terraform.State and its
downstream types with states.State, terraform.Plan with plans.Plan,
state.State with statemgr.State, and switch to the new implementations of
the state and plan file formats. However, due to the number of times those
types are used, this also ended up affecting numerous other parts of core
such as terraform.Hook, the backend.Backend interface, and most of the CLI
commands.
Just as with 5861dbf3fc49b19587a31816eb06f511ab861bb4 before, I apologize
in advance to the person who inevitably just found this huge commit while
spelunking through the commit history.
We shouldn't really need these because the plan is already filtered to
include diffs only for targeted resources, but we currently rely on this
to filter out non-resource items from the diff, and so we'll retain it
for now to avoid reworking how the apply-time graph builder works.
On the first pass here we erroneously assumed that this was redundant with
the backend settings embedded in the configuration itself. In practice,
users can override backend configuration when running "terraform init"
and so we need to record the _effective_ backend configuration.
Along with this, we also return the selected workspace name at the time
the plan was created so we'll later be able to produce a specialized error
for the situation of having the wrong workspace selected. This isn't
strictly required because we'll also check the lineage of the state, but
the error message that would result from that failure would be relatively
opaque and thus less helpful to the user.
Since schemas are required to interpret provider, resource, and
provisioner attributes in configs, states, and plans, these helpers intend
to make it easier to gather up the the necessary provider types in order
to preload all of the needed schemas before beginning further processing.
Config.ProviderTypes returns directly the list of provider types, since
at this level further detail is not useful: we've not yet run the
provider allocation algorithm, and so the only thing we can reliably
extract here is provider types themselves.
State.ProviderAddrs and Plan.ProviderAddrs each return a list of
absolute provider addresses, which can then be turned into a list of
provider types using the new helper providers.AddressedTypesAbs.
Since we're already using configs.Config throughout core, this also
updates the terraform.LoadSchemas helper to use Config.ProviderTypes
to find the necessary providers, rather than implementing its own
discovery logic. states.State is not yet plumbed in, so we cannot yet
use State.ProviderAddrs to deal with the state but there's a TODO comment
to remind us to update that in a later commit when we swap out
terraform.State for states.State.
A later commit will probably refactor this further so that we can easily
obtain schema for the providers needed to interpret a plan too, but that
is deferred here because further work is required to make core work with
the new plan types first. At that point, terraform.LoadSchemas may become
providers.LoadSchemas with a different interface that just accepts lists
of provider and provisioner names that have been gathered by the caller
using these new helpers.
The types in this package are intended to replace plan- and diff-related
types from the "terraform" package, although those older types must remain
for now so that they can be used to implement shims for older codepaths.
type "Changes" is approximately equivalent to terraform.Diff, but renamed
since it now describes whole objects before and after rather than an
attribute-level diff as before. The term "diff" is now reserved for the
visual rendition of the changes we'll display to the user, although
rendering of this new Changes model is not yet implemented.
