Cannot create a disk_snapshot_policy.

[bulowaty]

TL;DR

There is missing optional parameter in submodule compute_disk_snapshot variables.
snapshot_schedule originally accepts only one of: daily_schedule, hourly_schedule or weekly_schedule but in module it requests to define them all.

Expected behavior

module "disk_snapshots" {
  count  = var.enable_disks_snapshot ? 1 : 0
  source = "git@github.com:terraform-google-modules/terraform-google-vm.git?ref=v13.1.1"

  disks = [
    "${local.boot_disk_id}",
    "${google_compute_disk.data_disk.id}"
  ]
  module_depends_on = [
    "${google_compute_instance.instance.name}",
    "${google_compute_disk.data_disk.name}"
  ]
  name    = "${var.name}-snapshot-policy"
  project = var.project_id
  region  = var.region
  snapshot_properties = {
    labels          = var.labels
    guest_flush = false
    storage_locations = [
      var.region
    ]
  }
  snapshot_retention_policy = {
    max_retention_days    = var.snapshot_retention_days
    on_source_disk_delete = var.keep_snapshots_after_delete ? "KEEP_AUTO_SNAPSHOTS" : "APPLY_RETENTION_POLICY"
  }
  snapshot_schedule = {
    daily_schedule = {
      days_in_cycle = 1
      start_time    = var.snapshot_start_time
    }
  }
}

Then after plan I expect to create resources related to module
so in this particular example I have a one VM with two disks: boot and data
and it should create snapshot policy with attachment to both.

Observed behavior

When I'll set only one schedule (MARK: I kept others in errors commented for visibility)

  snapshot_schedule = {
    daily_schedule = {
      days_in_cycle = 1
      start_time    = var.snapshot_start_time
    }
  }

Then I have an error:

│ Error: Invalid value for input variable
│ 
│   on module/main.tf line 76, in module "disk_snapshots":
│   76:   snapshot_schedule = {
│   77:     daily_schedule = {
│   78:       days_in_cycle = 1
│   79:       start_time    = var.snapshot_start_time
│   80:     }
│   81:     #hourly_schedule = {
│   82:     #  hours_in_cycle = 24
│   83:     #  start_time     = var.snapshot_start_time
│   84:     #}
│   85:     #weekly_schedule = {
│   86:     #  day_of_weeks = [
│   87:     #    {
│   88:     #      day        = "MONDAY"
│   89:     #      start_time = var.snapshot_start_time
│   90:     #    },
│   91:     #    {
│   92:     #      day        = "TUESDAY"
│   93:     #      start_time = var.snapshot_start_time
│   94:     #    },
│   95:     #  ]
│   96:     #}
│   97:   }
│ 
│ The given value is not suitable for
│ module.vm.module.disk_snapshots.var.snapshot_schedule declared at
│ .terraform/modules/vm.disk_snapshots/modules/compute_disk_snapshot/variables.tf:42,1-29:
│ attributes "hourly_schedule" and "weekly_schedule" are required.

To satisfy the requirements I set them all

  snapshot_schedule = {
    daily_schedule = {
      days_in_cycle = 1
      start_time    = var.snapshot_start_time
    }
    hourly_schedule = {
      hours_in_cycle = 24
      start_time     = var.snapshot_start_time
    }
    weekly_schedule = {
      day_of_weeks = [
        {
          day        = "MONDAY"
          start_time = var.snapshot_start_time
        },
        {
          day        = "TUESDAY"
          start_time = var.snapshot_start_time
        },
      ]
    }
  }

And I got following error

│ Error: Invalid combination of arguments
│ 
│   with module.vm["<instance_name>"].module.disk_snapshots[0].google_compute_resource_policy.policy,
│   on .terraform/modules/vm.disk_snapshots/modules/compute_disk_snapshot/main.tf line 34, in resource "google_compute_resource_policy" "policy":
│   34:     schedule {
│ 
│ "snapshot_schedule_policy.0.schedule.0.daily_schedule": only one of
│ `snapshot_schedule_policy.0.schedule.0.daily_schedule,snapshot_schedule_policy.0.schedule.0.hourly_schedule,snapshot_schedule_policy.0.schedule.0.weekly_schedule`
│ can be specified, but
│ `snapshot_schedule_policy.0.schedule.0.daily_schedule,snapshot_schedule_policy.0.schedule.0.hourly_schedule,snapshot_schedule_policy.0.schedule.0.weekly_schedule`
│ were specified.
╵
╷
│ Error: Invalid combination of arguments
│ 
│   with module.vm["<instance_name>"].module.disk_snapshots[0].google_compute_resource_policy.policy,
│   on .terraform/modules/vm.disk_snapshots/modules/compute_disk_snapshot/main.tf line 34, in resource "google_compute_resource_policy" "policy":
│   34:     schedule {
│ 
│ "snapshot_schedule_policy.0.schedule.0.hourly_schedule": only one of
│ `snapshot_schedule_policy.0.schedule.0.daily_schedule,snapshot_schedule_policy.0.schedule.0.hourly_schedule,snapshot_schedule_policy.0.schedule.0.weekly_schedule`
│ can be specified, but
│ `snapshot_schedule_policy.0.schedule.0.daily_schedule,snapshot_schedule_policy.0.schedule.0.hourly_schedule,snapshot_schedule_policy.0.schedule.0.weekly_schedule`
│ were specified.
╵
╷
│ Error: Invalid combination of arguments
│ 
│   with module.vm["<instance_name>"].module.disk_snapshots[0].google_compute_resource_policy.policy,
│   on .terraform/modules/vm.disk_snapshots/modules/compute_disk_snapshot/main.tf line 34, in resource "google_compute_resource_policy" "policy":
│   34:     schedule {
│ 
│ "snapshot_schedule_policy.0.schedule.0.weekly_schedule": only one of
│ `snapshot_schedule_policy.0.schedule.0.daily_schedule,snapshot_schedule_policy.0.schedule.0.hourly_schedule,snapshot_schedule_policy.0.schedule.0.weekly_schedule`
│ can be specified, but
│ `snapshot_schedule_policy.0.schedule.0.daily_schedule,snapshot_schedule_policy.0.schedule.0.hourly_schedule,snapshot_schedule_policy.0.schedule.0.weekly_schedule`
│ were specified.

So the error says that I have to use only one of those possibilities.

Terraform Configuration

- Installing hashicorp/google v4.85.0...
- Installed hashicorp/google v4.85.0 (signed by HashiCorp)
- Installing hashicorp/null v3.2.3...
- Installed hashicorp/null v3.2.3 (signed by HashiCorp)

Terraform Version

Terraform v1.6.3
on linux_amd64

terragrunt version v0.53.2

Additional information

I forked this locally to check what can be done.
It just require a small improvement by adding optional( ) attribute for them as below.

variable "snapshot_schedule" {
  description = "The scheduled to be used by the snapshot policy. For more details see https://registry.terraform.io/providers/hashicorp/google/latest/docs/resources/compute_resource_policy#schedule"
  type = object(
    {
      daily_schedule = optional(object(
        {
          days_in_cycle = number
          start_time    = string
        }
      ))
      hourly_schedule = optional(object(
        {
          hours_in_cycle = number
          start_time     = string
        }
      ))
      weekly_schedule = optional(object(
        {
          day_of_weeks = set(object(
            {
              day        = string
              start_time = string
            }
          ))
        }
      ))
    }
  )
}