Terraform 0.14 release candidates are treated as Terraform versions prior to 0.12.0

[kiddom-kq]

I a moved a small project in our tf repo to the new 0.14.0 which has not quite had a stable release, yet. As of today (2020-11-30) the latest release is rc1.

To use this new TF version, I created a new entry in the atlantis.yaml file for the repo:

version: 3
projects:
  - dir: someCategory/someEntity
    # See: https://releases.hashicorp.com/terraform/
    terraform_version: v0.14.0-rc1

Note: I also tried a version of the atlantis.yaml file that didn't have the v prefix:terraform_version: 0.14.0-rc1, but this, too, resulted in the same issue. As soon as I tried 0.13.5 the 5 variables were no longer injected, but, of course, i get the warning:

Error refreshing state: state snapshot was created by Terraform v0.14.0, which is newer than current v0.13.5...

I manually ran plan on the collection of TF files in the someCategory/someEntity path and I got this back:

Error: Value for undeclared variable
A variable named "atlantis_repo_name" was assigned on the command line, but
the root module does not declare a variable of that name. To use this value,
add a "variable" block to the configuration.

The same error for a other variables:

• atlantis_user
• atlantis_repo
• atlantis_repo_name
• atlantis_repo_owner
• atlantis_pull_num

After a bit of digging, i see that those variables are set / fed in to the TF execution for versions of TF less than 12

// If using Terraform >= 0.12 we don't set any of these variables because
// those versions don't allow setting -var flags for any variables that aren't
// actually used in the configuration. Since there's no way for us to detect
// if the configuration is using those variables, we don't set them.
func (p *PlanStepRunner) tfVars(ctx models.ProjectCommandContext, tfVersion *version.Version) []string {
	if vTwelveAndUp.Check(tfVersion) {
		return nil
	}

	// NOTE: not using maps and looping here because we need to keep the
	// ordering for testing purposes.
	// NOTE: quoting the values because in Bitbucket the owner can have
	// spaces, ex -var atlantis_repo_owner="bitbucket owner".
	return []string{
		"-var",
		fmt.Sprintf("%s=%q", "atlantis_user", ctx.User.Username),
		"-var",
		fmt.Sprintf("%s=%q", "atlantis_repo", ctx.BaseRepo.FullName),
		"-var",
		fmt.Sprintf("%s=%q", "atlantis_repo_name", ctx.BaseRepo.Name),
		"-var",
		fmt.Sprintf("%s=%q", "atlantis_repo_owner", ctx.BaseRepo.Owner),
		"-var",
		fmt.Sprintf("%s=%d", "atlantis_pull_num", ctx.Pull.Num),

From here:

atlantis/server/events/runtime/plan_step_runner.go

Line 194 in 6ade4ba

func (p *PlanStepRunner) tfVars(ctx models.ProjectCommandContext, tfVersion *version.Version) []string {

Except, i'm using version 14 of terraform, and 14 > 12. So how is vTwelveAndUp.Check(tfVersion) implemented?

var vTwelveAndUp = MustConstraint(">=0.12-a")

And what about MustConstraint? How does it work?

// MustConstraint will parse one or more constraints from the given
// constraint string. The string must be a comma-separated list of
// constraints. It panics if there is an error.
func MustConstraint(v string) version.Constraints {
	c, err := version.NewConstraint(v)
	if err != nil {
		panic(err)
	}
	return c
}

which is a wrapper around this hashi lib: https://github.com/hashicorp/go-version

My GoLang is pretty weak, so I got lost trying to understand how the -a token is parsed by hashi's lib. I'm not sure if the
">=0.12-a" string needs to be updated or if there's an error in how Hashi's lib is parsing the -rc1 suffix on the version number.

[acastle]

Thank you very much for your detailed investigation @kiddom-kq! You are spot on with the root cause here and a patch is on the way.