Lock file is modified when running `terragrunt plan`

[gercograndia]

Describe the bug

When running terragrunt plan on a unit that holds both a terragrunt.hcl and .terraform.lock.hcl file, the lock file is modified. My underdstanding from this is that terragrunt should respect the lock file as being provided as part of the unit (and checked into git).

Steps To Reproduce

1. Check lock file in a freshly deployed unit (no .terragrunt-cache)

For example, it will hold a constraint like this:

provider "registry.opentofu.org/hashicorp/azuread" {
  version     = "3.3.0"
  constraints = ">= 2.35.0"
  hashes = [
   ...

2. Run a plan

terragrunt plan --terragrunt-non-interactive -out=planfile -lock=false

3. Check the lock file again

provider "registry.opentofu.org/hashicorp/azuread" {
  version     = "3.3.0"
  constraints = "3.3.0"
  hashes = [
   ...

Check the changed constraint.

In this particular example we see that the actual version doesn't change, however in other examples this is the case. Causing issues obviously.

Expected behavior

The lock-file should be respected and be read-only.

Versions

• Terragrunt version: v0.72.6
• OpenTofu version: v1.9.0
• MacOS

[gercograndia]

Probably related to this MR.

Indeed using the terraform provider cache.

Will await that MR and test again.