terraform fmt should accept `.tfbackend` files

[thiagowfx]

Terraform Version

% terraform version
Terraform v1.10.4

Use Cases

It should be possible to run terraform fmt on .tfbackend files, just like it is possible to do so in .tfvars files.

As of now:

$ terraform fmt a.tfbackend
│ Error: Only .tf, .tfvars, and .tftest.hcl files can be processed with terraform fmt

Wherein:

$ cat a.tfbackend
a = "foo"
b      = "bar"

.tfbackend is very similar to .tfvars as per the official docs.

The example docs also show the files nicely formatted (the equal signs are vertically aligned), suggesting that it is the intent.

Attempted Solutions

terraform fmt a.tfbackend does not work.

Renaming it to a.tfvars and then running terraform fmt a.tfvars works.

Proposal

Make terraform fmt accept *.tfbackend files, similarly to .tfvars.

References

No response

[radeksimko]

You can still format a file regardless of its name by piping its contents into fmt. For example:

cat any-file.any-ext | terraform fmt -

Bear in mind though that the file format is based on the earlier generation of HCL (1) and so there is no guarantee that it would always produce compatible output or be able to format it.

[yermulnik]

@radeksimko While this hint makes sense, it seems to be sort of natural for terraform fmt to support .tfbackend files too:

Usage: terraform [global options] fmt [options] [target...]

Rewrites all Terraform configuration files to a canonical format. […]

Though looking at the conversation in #36570 I seem to think implementation isn't going to be an easy thing =(

Do you by any chance know whether the .tfbackend has existed long before or is it something new? Asking as I actually TIL'ed about it when @thiagowfx filed another PR about it in the other repo. Thanks.

[yermulnik]

Looking at bb86860 from 2021, this looks to be a long-existed feature which I have never come across, though which was described to be using .hcl files before that commit.

[crw]

Thanks for this feature request! If you are viewing this issue and would like to indicate your interest, please use the 👍 reaction on the issue description to upvote this issue. We also welcome additional use case descriptions. Thanks again!

[crw]

For followers of this issue, I want to highlight the conversation of the closed and unmerged pull request #36570 -- specifically, that there is not a true definition of the tfbackend format and that the HCL-v2-based fmt command is not guaranteed to appropriately format a file based on an HCL v1 format.

The current work-around suggested by @radeksimko is likely to stand unless something changes in the implementation of fmt to support HCL v1 files. #36564 (comment)