Built-in providers are special providers that are distributed as part of
Terraform CLI itself, rather than being installed separately. They always
live in the terraform.io/builtin/... namespace so it's easier to see that
they are special, and currently there is only one built-in provider named
"terraform".
Previous commits established the addressing scheme for built-in providers.
This commit makes the installer aware of them to the extent that it knows
not to try to install them the usual way and it's able to report an error
if the user requests a built-in provider that doesn't exist or tries to
impose a particular version constraint for a built-in provider.
For the moment the tests for this are the ones in the "command" package
because that's where the existing testing infrastructure for this
functionality lives. A later commit should add some more focused unit
tests here in the internal/providercache package, too.
Due to some incomplete rework of this function in an earlier commit, the
safety check for using the same directory as both the target and the
cache was inverted and was raising an error _unless_ they matched, rather
than _if_ they matched.
This change is verified by the e2etest TestInitProviders_pluginCache,
which is also updated to use the new-style cache directory layout as part
of this commit.
Just as with the old installer mechanism, our goal is that explicit
provider installation is the only way that new provider versions can be
selected.
To achieve that, we conclude each call to EnsureProviderVersions by
writing a selections lock file into the target directory. A later caller
can then recall the selections from that file by calling SelectedPackages,
which both ensures that it selects the same set of versions and also
verifies that the checksums recorded by the installer still match.
This new selections.json file has a different layout than our old
plugins.json lock file. Not only does it use a different hashing algorithm
than before, we also record explicitly which version of each provider
was selected. In the old model, we'd repeat normal discovery when
reloading the lock file and then fail with a confusing error message if
discovery happened to select a different version, but now we'll be able
to distinguish between a package that's gone missing since installation
(which could previously have then selected a different available version)
from a package that has been modified.
We've been using the models from the "moduledeps" package to represent our
provider dependencies everywhere since the idea of provider dependencies
was introduced in Terraform 0.10, but that model is not convenient to use
for any use-case other than the "terraform providers" command that needs
individual-module-level detail.
To make things easier for new codepaths working with the new-style
provider installer, here we introduce a new model type
getproviders.Requirements which is based on the type the new installer was
already taking as its input. We have new methods in the states, configs,
and earlyconfig packages to produce values of this type, and a helper
to merge Requirements together so we can combine config-derived and
state-derived requirements together during installation.
The advantage of this new model over the moduledeps one is that all of
recursive module walking is done up front and we produce a simple, flat
structure that is more convenient for the main use-cases of selecting
providers for installation and then finding providers in the local cache
to use them for other operations.
This new model is _not_ suitable for implementing "terraform providers"
because it does not retain module-specific requirement details. Therefore
we will likely keep using moduledeps for "terraform providers" for now,
and then possibly at a later time consider specializing the moduledeps
logic for only what "terraform providers" needs, because it seems to be
the only use-case that needs to retain that level of detail.
When a provider source produces an HTTP URL location we'll expect it to
resolve to a zip file, which we'll first download to a temporary
directory and then treat it like a local archive.
When a provider source produces a local archive path we'll expect it to
be a zip file and extract it into the target directory.
This does not yet include an implementation of installing from an
already-unpacked local directory. That will follow in a subsequent commit,
likely following a similar principle as in Dir.LinkFromOtherCache.
These new functions allow command implementations to get hold of the
providercache objects and installation source object derived from the
current CLI configuration.
This is not tested yet, but it's a compilable strawman implementation of
the necessary sequence of events to coordinate all of the moving parts
of running a provider installation operation.
This will inevitably see more iteration in later commits as we complete
the surrounding parts and wire it up to be used by "terraform init". So
far, it's just dead code not called by any other package.
The Installer type will encapsulate the logic for running an entire
provider installation request: given a set of providers to install, it
will determine a method to obtain each of them (or detect that they are
already installed) and then take the necessary actions.
So far it doesn't do anything, but this stubs out an interface by which
the caller can request ongoing notifications during an installation
operation.
