Add support for `.terraform-version` file

[lukasz-mitka]

Same way actions/setup-node or actions/setup-python handle setting version from a file.
It could default to .terraform-version file as tfenv already uses it: https://github.com/tfutils/tfenv#terraform-version-file and matches pattern for other actions.

[gunta]

Something like this logic would work perfect
https://github.com/actions/setup-node/blob/ae9f0f7448e93b1be0f44663e79763dbdffcc4da/src/main.ts#L80

[Crisfole]

  - name: Get Terraform Version
    id: tf_version
    run: |
      echo "value=$(cat .terraform-version)" >> $GITHUB_OUTPUT

Then later you can ${{ steps.env_name.outputs.value }}

[lukasz-mitka]

@Crisfole this is a good workaround, but the idea is to have built-in solution like other actions have (https://github.com/actions/setup-node or https://github.com/actions/setup-python)

Also please fix your snippet. It should be ${{ steps.tf_version.outputs.value }}

[pioneer2k]

There are other tools on the market that uses this mechanism, like Mend Renovate for creating automated pull requests for dependency updates: https://docs.renovatebot.com/modules/manager/terraform-version/

[Crisfole]

@Crisfole this is a good workaround, but the idea is to have built-in solution like other actions have

Oh, for sure! But two years from now when I Google this again I want to have that comment available to me! 😆

[lvjp]

Why do not compute the version from the definition file.
I think that if we care about versioning, we must have a provider.tf like this :

terraform {
  required_version = "~> 1.10.0"
}

Maybe, an implementation like action/setup-go will be good and look like this :

uses: hashicorp/setup-terraform@b9cd54a3c349d3f38e8881555d616ced269862dd # v3.1.2
with:
    terraform_version_file: provider.tf

This solution permits to not maintain version condition in two files instead of only in the terraform definitions.

[kittydoor]

These are two different things.

The constraints in the provider.tf specify lower and upper boundaries for support of terraform cli for the specific module.

.terraform-version file specifies the actively in use terraform version.

The constraints can be ~> 1.10.0 but you want to in you CI use 1.10.1 exactly rather than leave it to chance, and thus .terraform-version exists.