Since terraform-bundle is just a different frontend to Terraform's module
installer, it is subject to the same installation constraints as Terraform
itself.
Terraform 0.12 cannot install providers targeting Terraform 0.11 and
earlier, and so therefore terraform-bundle built with Terraform 0.12
cannot either. A build of terraform-bundle from the v0.11 line must be
used instead.
Without this change, the latest revisions of terraform-bundle would
install plugins for Terraform 0.12 to bundle along with Terraform 0.10 or
0.11, which will not work at runtime due to the plugin protocol mismatch.
Until now, terraform-bundle was incorrectly labelled with its own version
number even though in practice it has no version identity separate from
Terraform itself. Part of this change, then, is to make the
terraform-bundle version match the Terraform version it was built against,
though any prior builds will of course continue to refer to themselves
as 0.0.1.
If asked to create a bundle for a version of Terraform v0.12 or greater,
an error will be returned instructing the user to use a build from the
v0.11 branch or one of the v0.11.x tags in order to bundle those versions.
This also includes a small fix for a bug where the tool would not fail
properly when the requested Terraform version is not available for
installation, instead just producing a zip file with no "terraform"
executable inside at all. Now it will fail, allowing automated build
processes to detect it and not produce a broken archive for distribution.
Normally "terraform init" will download and install the plugins necessary
to work with a particular configuration, but sometimes Terraform is
deployed in a network that, for one reason or another, cannot access the
official plugin repository for automatic download.
terraform-bundle provides an alternative method, allowing the
auto-download process to be run out-of-band on a separate machine that
_does_ have access to the repository. The result is a zip file that can
be extracted onto the target system to install both the desired
Terraform version and a selection of providers, thus avoiding the need
for on-the-fly plugin installation.
This is provided as a separate tool from Terraform because it is not
something that most users will need. In the rare case where this is
needed, we will for the moment assume that users are able to build this
tool themselves. We may later release it in a pre-built form, if it proves
to be generally useful.
It uses the same API from the plugin/discovery package is is used by the
auto-install behavior in "terraform init", so plugin versions are resolved
in the same way. However, it's expected that several different Terraform
configurations will run from the same bundle, so this tool allows the
bundle to include potentially many versions of the same provider and thus
allows each Terraform configuration to select from the available versions
in the bundle, avoiding the need to upgrade all configurations to new
provider versions in lockstep.
Martin Atkins