Terragrunt OpenTofu: reset terraform_version when changing tool

[truszkowski]

Description of the change

Let's reset the version when we're changing the terragrunt tool.

Step 1 - now we have computed the latest for terraform (1.5.7)

resource spacelift_stack this {
  ...
  terragrunt {
    tool = "TERRAGRUNT_FOSS"
  }
}

Step 2 - we expect the latest for opentofu (1.7.1)

resource spacelift_stack this {
  ...
  terragrunt {
    tool = "OPEN_TOFU"
  }
}

Let's reset terraform_version when we're changing tool and terraform_version is not specified in the config.

Let's also take care of terraform_workflow_tool. It's the same situation. We should reset terraform_version in the case of the tool change.

resource spacelift_stack this {
  ...
  terraform_workflow_tool = "TERRAFORM_FOSS"
  ...
}

into:

resource spacelift_stack this {
  ...
  terraform_workflow_tool = "CUSTOM"
  ...
}

Type of change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation (non-breaking change that adds documentation)

Related issues

Fix #1

Checklists

Development

• Lint rules pass locally
• The code changed/added as part of this pull request has been covered with tests
• All tests related to the changed code pass in development
• Examples for new resources and data sources have been added
• Default values have been documented in the description (e.g., "Dummy: (Boolean) Blah blah. Defaults to false.)
• If the action fails that checks the documentation: Run go generate to make sure the docs are up to date

Code review

• This pull request has a descriptive title and information useful to a reviewer. There may be a screenshot or screencast attached
• Pull Request is no longer marked as "draft"
• Reviewers have been assigned
• Changes have been reviewed by at least one other engineer

[lorengordon]

Some interesting overlap here with the issue I opened recently, #540

[truszkowski]

When I changing TERRAFORM_FOSS -> OPEN_TOFU:

And it works but produces a warning:

I've tried to convince Terraform to ignore/handle that but it didn't work.

[truszkowski]

I've tried to convince Terraform to ignore/handle that but it didn't work.

I thought CustomizeDiff should help, but no. At the stack level, I can't:

I could SetNewComputed("terragrunt") but then showed the plan is more misleading

So, I'll keep it as is:

If we turn on warnings (TF_LOG=warn), we can see the provider silently replaced terraform_version:

[truszkowski]

I've also fixed tests ("terraform-default-" prefix).

[adamconnelly]

LGTM

[marcinwyszynski]

Will it make sense to extend this PR to also fix #547 ? Looks like it's almost the same issue, just with plain Terraform.

[peterdeme]

@truszkowski we merged a fix to the unit tests, can you rebase this? 🙏

[truszkowski]

Will it make sense to extend this PR to also fix #547 ? Looks like it's almost the same issue, just with plain Terraform.

I've made it. So, now, we'll reset terraform_version (if not specified) during terraform_workflow_tool change.