OpenTofu vs Terraform internals

[rlees85]

I just wondered if there was any plan for Terragrunt to fully adopt OpenTofu over Terraform? I can see the project kind of does back OpenTofu more however I've noticed some inconsistencies when using Terragrunt:

• When loading credentials for module repositories, it ignores .tofurc but reads .terraformrc just fine. Looking at the code, its pulling in some hashicorp/terraform deps to handle this.

• Much more annoyingly, having variables/locals in the source for a Terraform module causes Terragrunt to crap out when running terragrunt hcl validate --all --inputs. I assume this is because it is using Terraform internals again to figure out what inputs are needed vs OpenTofu

[yhakbar]

Hey @rlees85 ,

We very much have an explicit stance of supporting OpenTofu, and are very much invested in OpenTofu being the best tool to use with Terragrunt. 😄

What you're seeing there is the fact that these integrations were put in place when Terraform was MPL, and OpenTofu didn't exist. We prioritize adding integrations with OpenTofu-specific functionality, in accordance with what we understand to be important to the community. So, I appreciate you surfacing these gaps. We also have to balance prioritizing adding those integrations with features that are specific to Terragrunt, and have nothing to do with OpenTofu or Terraform specifically, and we have a lot planned for Terragrunt in that regard!

If you're interested in doing the development work to get those integrations sorted out, that would fast track adding the features. Regardless, I would recommend you create an issue to request each enhancement (assuming one doesn't already exist), so we can schedule the work accordingly. I'd be happy to work with you on becoming a contributor, and learning what you need to make the updates. I can chat with you in the Terragrunt Discord as well if it makes things easier for you.

[rlees85]

Hello, thanks very much for your reply! I understand now that it is not a simple switch between Terraform and OpenTofu internals/packages. It looks like there are various repos scattered about that provide various bits of functionality and some are not (yet) provided by OpenTofu.

I have opened two issues:
#4985
#4986

I believe the .tofurc one should be an easy fix and I will perhaps have a go at that. The one that is more of a pain (the validation one) might be a bit harder for me and may require some input from someone more involved in OpenTofu itself.

I have added everything I know technically to each issue also.