Add tofu to format on save list

[dpiddock]

A follow-on from #193, this adds the tofu extensions to the format-on-save list.

[dimbleby]

I'm inclined to think that #193 was a mistake and should be undone, rather than going further down that path.

Are .tofu and .tf files the same or not?

• if yes, then folk can either use the .tf extension all along, or else set up their own filetype detection
• if no, then it is a mistake to treat them as if they are the same

What I don't want is to slip gradually into accidental support for a non-terraform filetype

[yermulnik]

Are .tofu and .tf files the same or not?

They are the same. OpenTofu prefers .tofu over .tf files if they have the same base name, but otherwise OpenTofu reads both. Terraform ignores .tofu files obviously.
Ref: https://opentofu.org/docs/language/files/

ps: I'm not a user of OpenTofu though, just wanted to add clarity FWIW.

[ab]

Ping on this? It's pretty confusing having .tofu files recognized by vim-terraform for file type detection but not for auto-formatting. (It took me a while to figure out why they weren't getting formatted.)

As far as syntax goes, they're currently the same and compatible. Although they certainly could diverge at some point in the future.

terraform fmt normally doesn't accept .tofu files on the command line, but because terraform#fmt() passes the buffer in on stdin, there's no compatibility issue at present.

I'd vote for merging as is, but an alternative possibility might be to introduce a setting like g:terraform_use_opentofu, which would set g:terraform_binary_path = 'tofu' and also add the .tofu file types.

[dimbleby]

I still think I would prefer just to revert #193, users who care about .tofu can add their own autocmds