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.
The public interface for loading schemas is Context.Schemas, which can
take into account the context's records of which plugin versions and
checksums we're expecting. loadSchemas is an implementation detail of
that, representing the part we run only after we've verified all of the
plugins.
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.
