Investigate / test tfenv usage or other script like executable wrappers

[paultyng]

This is mostly relevant to the LS, but something we should investigate.

Known wrappers

See https://github.com/hashicorp/terraform-exec/issues/6#issuecomment-703315302 for more details.

tfenv

terraform on path is now a shell script: yes Terraform version may depend on working directory: yes

terraform-switcher

terraform on path is now a shell script: no Terraform version may depend on working directory: yes

homebrew-terraforms

terraform on path is now a shell script: no Terraform version may depend on working directory: no

asdf

terraform on path is now a shell script: unknown Terraform version may depend on working directory: unknown

[kmoe]

also possibly https://warrensbox.github.io/terraform-switcher/

[kmoe]

See https://github.com/hashicorp/terraform-ls/issues/128 for unexpected behaviour cased by using a wrapper script to set appropriate env vars.

[paultyng]

At least warn or let consumers know if these tools are being used, even if we aren't going to handle it.

[kmoe]

Another one: https://github.com/Yleisradio/homebrew-terraforms

[kmoe]

Results of investigation. Branch tfenv-etc contains some Dockerfiles for experimenting with these utilities in a clean environment (except homebrew-terraforms, which is only available for macOS).

tfenv

Installing tfenv adds a shell script named terraform to the $PATH, so which terraform resolves to this script. This script checks whether $TFENV_ROOT/version is set, and errors if not. An error will also be logged if the user has not selected a version with tfenv use.

Currently, this means that any use of tfinstall.LookPath() will error and not fall through to the next ExecPathFinder, because it assumes that if it finds a terraform binary then it must report terraform version properly. Recommend relaxing this and will open PR to do so.

terraform on path is now a shell script: yes Terraform version may depend on working directory: yes

terraform-switcher

Installing a Terraform version via tfswitch replaces any existing Terraform binary with a symlink. This is only done when installing a new version of Terraform, so unlike tfenv there is no risk of the binary or script at which terraform not pointing to Terraform itself.

terraform on path is now a shell script: no Terraform version may depend on working directory: yes

homebrew-terraforms

The most conservative of the three helpers, this simply provides a chtf utility which allows the user to install and (with caching) switch between various versions of Terraform via the brew package manager. It therefore has no more impact on tfexec than brew itself.

terraform on path is now a shell script: no Terraform version may depend on working directory: no

Conclusion & recommendations

• tfinstall.LookPath() - do not error out when an executable named terraform is found but terraform version does not return reasonable output; fall through to the next method instead.
• Add note to README warning users of helpers that if the terraform on their path resolves to a different version depending on working directory, this will also be true of the Terraform executable located by tfinstall.LookPath().
• If necessary, open separate issue to deal with env passthrough / direnv issue as described in https://github.com/hashicorp/terraform-ls/issues/128#issuecomment-662701186 (follow up with @radeksimko).

[kvendingoldo]

btw. you can also use tenv that support Terraform as well as OpenTofu (and Terragrunt :) ) in one tool. It allow you to simplify version management and can do much more, than tfswitch.