fix: Set Terraform plan file as last argument in apply-all

[amontalban]

This PR should fix #1271 (The position of the Terraform plan file in the apply-all command).

I'm having the same problem as @ibacalu when running Terragrunt with:

  extra_arguments "save_plan" {
    commands = [
      "plan"
    ]

    arguments = [
      "-out=${get_terragrunt_dir()}/${trimspace(run_cmd("basename", "${get_terragrunt_dir()}"))}.tfplan"
    ]
  }

  extra_arguments "load_plan" {
    commands = [
      "apply"
    ]

    arguments = [
      "${get_terragrunt_dir()}/${trimspace(run_cmd("basename", "${get_terragrunt_dir()}"))}.tfplan"
    ]
  }

And then running plan-all and apply-all (I am aware that this is an antipattern as described by @yorinasub17 but I think it needs to be fixed anyway).

Thanks!

[brikis98]

Thanks for the PR! I suspect the current approach will not work correctly. To know for sure, this PR will need tests to validate the behavior. Check out test/integration_test.go and the fixtures it uses to see how to structure such a test.

[brikis98]

Hm, I'm not sure this is a safe assumption to make. That is, it's possible to have a different arg passed to Terraform that is a file—or worse yet, happens to match the name of a valid file—but isn't a plan file. Here's an example:

terraform apply \ 
  -state foo.tfstate \
  -var foo=bar

If there's a foo.tfstate already, the code above will move that parameter to the end of the command, as if it's a plan file.

[amontalban]

Thank you @brikis98, I haven't considered that use case. I will write a test as well as validating the current ones work fine and come back to you.