terraform-provider-google: Setting redis maintenance_policy causes creation of unexpected config block of maintenance_schedule

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Terraform Version

Terraform v0.13.7

Affected Resource(s)

resource “google_redis_instance”

Terraform Configuration Files

resource "google_redis_instance" "cache_instance" {
  name           = "cache-instance"
  tier           = "STANDARD_HA"
  memory_size_gb = 2

  location_id             = local.gcp_zones[0]
  alternative_location_id = local.gcp_zones[1]
  authorized_network      = local.network
  connect_mode            = "PRIVATE_SERVICE_ACCESS"
  labels                  = local.labels

  maintenance_policy {
    weekly_maintenance_window {
      day = "SUNDAY"
      start_time {
        hours = 9
      }
    }
  }
}

Debug Output

https://gist.github.com/yonicurv/1a9006c0ec9bee33f4ce13c01f19835d

Expected Behavior

Do not try to remove scheduled maintenance.

Actual Behavior

Tries to remove and fails with : Error 400: Invalid option ‘maintenance_schedule’: ‘maintenance_schedule’ cannot be updated on existing instances.

Steps to Reproduce

1. terraform apply
2. Let GCP to schedule next maintenance.
3. terraform apply

Workaround

Add the following block to ignore any changes related to maintenance_schedule, and preserve the configuration of maintenance_policy for future schedules.

  lifecycle {
    ignore_changes = [
      maintenance_schedule,
    ]
  }

References

https://github.com/hashicorp/terraform-provider-google/pull/10978 https://github.com/hashicorp/terraform-provider-google/issues/9622