fix: auto plan when .terraform.lock.hcl changed

[shouichi]

what

When projects are specified and when_modified is not specified via
the config file, changing .terraform.lock.hcl file won't trigger auto
plan. This is because the default raw.WhenModified does not include
.terraform.lock.hcl.

Note that when projects are auto detected, changing
.terraform.lock.hcl triggers auto plan. This is because the
cmd.DefaultAutoplanFileList includes .terraform.lock.hcl.

why

It is desirable to run terraform plan/apply even if only .terraform.lock.hcl are updated.

tests

I added a unit test and also tested this behavior by running atlantis with this change.

references

See also #3466.

[jamengual]

This can be done in the default or custom workflow by changing the autoplan triggered files or https://www.runatlantis.io/docs/server-configuration.html#autoplan-file-list, why to change it in atlantis code?

[shouichi]

Thank you, I didn't know that feature. But I think it's a good default. I was surprised that Atlantis didn't run auto plan when the lock file was changed.

[jamengual]

This default does not work for a lot of people that do not commit the lock file, that is the problem.

[nitrocode]

Tests are failing and no new tests have been added in this pr for coverage.

What cases would someone only update the lock file and not the hcl files themselves?

[shouichi]

I usually set relatively relaxed version constraints on HCL and exact versions are set by .terraform.lock.hcl.

# version.tf
terraform {
  required_providers {
    random = {
      source  = "hashicorp/random"
      version = "~> 3.0"
    }
  }
}

# .terraform.lock.hcl
provider "registry.terraform.io/hashicorp/random" {
  version     = "3.5.1"
  constraints = "~> 3.0"
  hashes = [...]
}

When I update provider versions by terraform init -upgrade only .terraform.lock.hcl is updated. In this scenario, I want to run terraform apply to minimize the risk of the provider version update. I think it's a good practice and it would be great if atlantis runs the auto-plan without configuring it.

If this makes sense, I'd like to fix/add tests to cover the new scenario where only .terraform.lock.hcl is modified. If it doesn't, feel free to close this. Thank you.

[nitrocode]

To me, your change makes sense. Thank you for contributing. My only issue is the lack of tests.

cc: @jamengual @GenPage thoughts?

[jamengual]

it is fine with me as long as there are tests.

[shouichi]

Could you help me to write tests? I found

atlantis/server/controllers/events/events_controller_e2e_test.go

Lines 705 to 718 in 0231970

	{
	Description: "Modified .terraform.lock.hcl triggers autoplan ",
	RepoDir: "simple-with-lockfile",
	ModifiedFiles: []string{".terraform.lock.hcl"},
	ExpAutoplan: true,
	Comments: []string{
	"atlantis plan",
	},
	ExpReplies: [][]string{
	{"exp-output-autoplan.txt"},
	{"exp-output-plan.txt"},
	},
	LockFileTracked: true,
	},

and it seems like this already tests if modifying .terraform.lock.hcl runs the auto-plan. But atlantis v0.24 won't run auto-plan when only .terraform.lock.hcl is modified. Am I missing something?

[shouichi]

@nitrocode I added a unit test and updated the PR description. Can you take a look?

[GenPage]

Thank you for the contribution @shouichi