Unfortunately in the user model the noun "source" is already used for the
argument in the required_providers block to specify which provider to use,
so it's confusing to use the same noun to also refer to the method used to
obtain that provider.
In the hope of mitigating that confusion, here we use the noun "method",
as in "installation method", to talk about the decision between getting
a provider directly from its origin registry or getting it from some
mirror. This is distinct from the provider's "source", which is the
location where a provider _originates_ (prior to mirroring).
This noun is also not super awesome, but better than overloading an
existing term in the same feature.
An earlier commit added a redundant stub for a new network mirror source
that was already previously stubbed as HTTPMirrorSource.
This commit removes the unnecessary extra stub and changes the CLI config
handling to use it instead. Along the way this also switches to using a
full base URL rather than just a hostname for the mirror, because using
the usual "Terraform-native service discovery" protocol here doesn't isn't
as useful as in the places we normally use it (the mirror mechanism is
already serving as an indirection over the registry protocol) and using
a direct base URL will make it easier to deploy an HTTP mirror under
a path prefix on an existing static file server.
If the CLI configuration contains a provider_installation block then we'll
use the source configuration it describes instead of the implied one we'd
build otherwise.
This more closely replicates the 0.12-and-earlier behavior, where having
at least one version of a provider installed locally would totally disable
any attempt to look for newer versions remotely.
This is just for the implicit default behavior. Assumption is that later
we'll have an explicit configuration mechanism that will allow the user
to specify exactly where to look for what, and thus avoid tricky
heuristics like this.
This restores some of the local search directories we used to include when
searching for provider plugins in Terraform 0.12 and earlier. The
directory structures we are expecting in these are different than before,
so existing directory contents will not be compatible without
restructuring, but we need to retain support for these local directories
so that users can continue to sideload third-party provider plugins until
the explicit, first-class provider mirrors configuration (in CLI config)
is implemented, at which point users will be able to override these to
whatever directories they want.
This also includes some new search directories that are specific to the
operating system where Terraform is running, following the documented
layout conventions of that platform. In particular, this follows the
XDG Base Directory specification on Unix systems, which has been a
somewhat-common request to better support "sideloading" of packages via
standard Linux distribution package managers and other similar mechanisms.
While it isn't strictly necessary to add that now, it seems ideal to do
all of the changes to our search directory layout at once so that our
documentation about this can cleanly distinguish "0.12 and earlier" vs.
"0.13 and later", rather than having to document a complex sequence of
smaller changes.
Because this behavior is a result of the integration of package main with
package command, this behavior is verified using an e2etest rather than
a unit test. That test, TestInitProvidersVendored, is also fixed here to
create a suitable directory structure for the platform where the test is
being run. This fixes TestInitProvidersVendored.
