Permanent Terraform diff on Azure

[johananl]

When deploying on Azure, terraform plan always shows a diff on the worker scale set which causes a re-creation of all the workers:

Terraform will perform the following actions:

-/+ module.johannes-test.module.workers.azurerm_monitor_autoscale_setting.workers (new resource required)
      id:                                                                                              "/subscriptions/.../resourceGroups/johannes-test/providers/microsoft.insights/autoscalesettings/johannes-test-maintain-desired" => <computed> (forces new resource)
      enabled:                                                                                         "true" => "true"
      location:                                                                                        "westeurope" => "westeurope"
      name:                                                                                            "johannes-test-maintain-desired" => "johannes-test-maintain-desired"
      profile.#:                                                                                       "1" => "1"
      profile.0.capacity.#:                                                                            "1" => "1"
      profile.0.capacity.0.default:                                                                    "2" => "2"
      profile.0.capacity.0.maximum:                                                                    "2" => "2"
      profile.0.capacity.0.minimum:                                                                    "2" => "2"
      profile.0.name:                                                                                  "default" => "default"
      resource_group_name:                                                                             "johannes-test" => "johannes-test"
      tags.%:                                                                                          "0" => <computed>
      target_resource_id:                                                                              "/subscriptions/.../resourceGroups/johannes-test/providers/Microsoft.Compute/virtualMachineScaleSets/johannes-test-workers" => "${azurerm_virtual_machine_scale_set.workers.id}" (forces new resource)

-/+ module.johannes-test.module.workers.azurerm_virtual_machine_scale_set.workers (new resource required)
      id:                                                                                              "/subscriptions/.../resourceGroups/johannes-test/providers/Microsoft.Compute/virtualMachineScaleSets/johannes-test-workers" => <computed> (forces new resource)
      automatic_os_upgrade:                                                                            "false" => "false"
      eviction_policy:                                                                                 "" => "Delete" (forces new resource)
      identity.#:                                                                                      "0" => <computed>
...

Steps to reproduce

1. Create an Azure cluster using the docs.
2. After terraform apply completes, run terraform plan again. A diff is shown.

[invidian]

It is now fixed in typhoon poseidon/typhoon@28506df#diff-da21b06db37ed8a8289fc79eb4cb5405, and fix for Terraform 0.11.X seem non-trivial (allow eviction_policy parameter in provider to accept empty string and then convert it to null if it's empty), so I think the reasonable thing to do would be to upgrade to Terraform 0.12.

[johananl]

OK. We are already tracking the 0.12 upgrade internally.