terraform_unused_declarations provider check should be configurable

[tomelliff]

This feels a little https://xkcd.com/1172/ but v0.14.0's addition of checking for unused providers with no configuration broke CI for us because we define a big file of AWS provider definitions across accounts and regions in one place and then symlink that around so we can refer to aws.accountname_region for provider aliases and not have to copy and paste the definition everywhere.

This is mostly because we have a lot of cross account role assumption stuff going on which we're slowly pulling out of things and then we could more nicely symlink to a more well scoped provider setup but for now it's what we have.

Could we get a configuration option to the rule to check what things the rule should check?

I'm thinking something like this:

rule "terraform_unused_declarations" {
  enabled = true

  data_sources = true
  locals       = true
  providers    = true
  variables    = true
}

[bendrucker]

Appreciate the reference 😄 — see also Hyrum's Law

We generally try to avoid this sort of configuration being implemented at the rule level in favor of annotations to simply ignore the rule altogether. This keeps the scope of the ignore minimal and its purpose clear.

[tomelliff]

Thanks.

So you'd recommend a # tflint-ignore: terraform_unused_declarations on all of those generated and symlinked provider definitions?

[bendrucker]

If you can, tflint-ignore-file: terraform_unused_declarations at the top of your generated files is the cleanest way to deal with this. There are issues out there regarding things like a --exclude flag but no consensus on the need (terraform-linters/tflint#2126). If you'd struggle to do file-level annotations for some reason, feel free to chime in there on why config/flags would be better.