Add support for legacy parsing of main.tf

[hinricht]

Is your feature request related to a problem? Please describe.

We'd like to use the main.tf/main.tofu file to pin the opentofu version, just like the terraform plugin does (i.e. https://github.com/asdf-community/asdf-hashicorp/blob/master/bin/parse-legacy-file).

See also the legacy version files documentaion

Describe the solution you'd like

We'd like the plugin to be able to

• parse main.tf for an opentofu version contraint
• parse .opentofu-version for an opentofu version contraint (although not that important to us, but this would make it feature-complete to asdf-hashicorp

Describe alternatives you've considered

• Pinning the opentofu version in .mise.toml is an option, although this leads to 2 places where the tofu version is pinned (.mise.toml and main.tofu)

Additional context

None

[hinricht]

@virtualroot Would you accept a PR ?

[virtualroot]

Hi @hinricht 👋 many thanks for opening this feature request.

I'm happy to accept a PR if you and others are willing to resolve any bugs that may appear after the feature is released.

Currently, I do not use mise or legacy_version_file, and I do not have time to maintain it after the release.

wdyt?

[hinricht]

@virtualroot Nice, I'll see when I can work on this, and will create a PR.

[hinricht]

Here it is, hope it works!

[hinricht]

Btw, I'm using mise and noticed that with this change, mise is able to set the tofu version from a main.tofu. but not from a file with a different name (even when I export the ASDF_OPENTOFU_VERSION_FILE env var to this file name).
I checked with the asdf-terradform plugin and it's the same.

Therefore I created a mise issue to track this error: jdx/mise#2602

Just fyi.

[virtualroot]

Thanks for the heads-up!