tools/terraform-bundle: refuse to bundle versions <0.12.0

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.

tools/terraform-bundle/README.md

@@ -32,6 +32,15 @@ $ go install ./tools/terraform-bundle
 This will install `terraform-bundle` in `$GOPATH/bin`, which is assumed by
 the rest of this README to be in `PATH`.
 
+`terraform-bundle` is a repackaging of the module installation functionality
+from Terraform itself, so for best results you should build from the tag
+relating to the version of Terraform you plan to use. There is some slack in
+this requirement due to the fact that the module installation behavior changes
+rarely, but please note that in particular bundles for versions of
+Terraform before v0.12 must be built from a `terraform-bundle` built against
+a Terraform v0.11 tag at the latest, since Terraform v0.12 installs plugins
+in a different way that is not compatible.
+
 ## Usage
 
 `terraform-bundle` uses a simple configuration file to define what should

tools/terraform-bundle/config.go

@@ -8,6 +8,8 @@ import (
 	"github.com/hashicorp/terraform/plugin/discovery"
 )
 
+var zeroTwelve = discovery.ConstraintStr(">= 0.12.0").MustParse()
+
 type Config struct {
 	Terraform TerraformConfig                      `hcl:"terraform"`
 	Providers map[string][]discovery.ConstraintStr `hcl:"providers"`
@@ -42,9 +44,14 @@ func (c *Config) validate() error {
 		return fmt.Errorf("terraform.version is required")
 	}
 
-	if _, err := c.Terraform.Version.Parse(); err != nil {
+	var v discovery.Version
+	var err error
+	if v, err = c.Terraform.Version.Parse(); err != nil {
 		return fmt.Errorf("terraform.version: %s", err)
 	}
+	if !zeroTwelve.Allows(v) {
+		return fmt.Errorf("this version of terraform-bundle can only build bundles for Terraform v0.12 and later; build terraform-bundle from the v0.11 branch or a v0.11.* tag to construct bundles for earlier versions")
+	}
 
 	if c.Providers == nil {
 		c.Providers = map[string][]discovery.ConstraintStr{}

tools/terraform-bundle/main.go

@@ -33,16 +33,14 @@
 package main
 
 import (
+	"io/ioutil"
 	"log"
 	"os"
 
-	"io/ioutil"
-
+	tfversion "github.com/hashicorp/terraform/version"
 	"github.com/mitchellh/cli"
 )
 
-const Version = "0.0.1"
-
 func main() {
 	ui := &cli.ColoredUi{
 		OutputColor: cli.UiColorNone,
@@ -64,7 +62,7 @@ func main() {
 		log.SetOutput(ioutil.Discard)
 	}
 
-	c := cli.NewCLI("terraform-bundle", Version)
+	c := cli.NewCLI("terraform-bundle", tfversion.Version)
 	c.Args = os.Args[1:]
 	c.Commands = map[string]cli.CommandFactory{
 		"package": func() (cli.Command, error) {

tools/terraform-bundle/package.go

@@ -135,6 +135,7 @@ func (c *PackageCommand) Run(args []string) int {
 
 	if err != nil {
 		c.ui.Error(fmt.Sprintf("Failed to fetch core package from %s: %s", coreZipURL, err))
+		return 1
 	}
 
 	c.ui.Info(fmt.Sprintf("Fetching 3rd party plugins in directory: %s", pluginDir))