Pass [] in zones of azurerm_public_ip will result a zone-redundant IP instead of a No Zone IP

[windwindblow]

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Terraform (and AzureRM Provider) Version

Terraform v0.12.31
AzureRM v2.58.0

Affected Resource(s)

• azurerm_public_ip

Terraform Configuration Files

resource "azurerm_public_ip" "example_ip" {
  name = "ip_name"
  location = "East US"
  resource_group_name = "resource_group"
  sku = "Standard"
  allocation_method = "Static"
  zones = []
}

Expected Behaviour

A standard public IP address with "No Zone" should be created even if the region supports the Zone-redundant.

Actual Behaviour

A standard public IP address with Zone-redundant (zones are [1,2,3]) are created.

Steps to Reproduce

resource "azurerm_public_ip" "example_ip" {
  name = "ip_name"
  location = "East US"
  resource_group_name = "resource_group"
  sku = "Standard"
  allocation_method = "Static"
  zones = []
}

1. terraform apply

References

Checking the Azure logs, if we put [] in the Terraform zones, [] will be omitted in the request. This leads Azure to create a zone redundant IP by default.
"requestbody": "{"location":"eastus","properties":{"idleTimeoutInMinutes":4,}],"publicIPAddressVersion":"IPv4","publicIPAllocationMethod":"Static"},"sku":{"name":"Standard"},"tags":{}}"

If we do the similar steps in Azure, you will see [] is sent as a valid zone parameter.
"requestbody": "{"sku":{"name":"Standard"},"properties":{"publicIPAllocationMethod":"Static"}]},"zones":[],"location":"East US"}",

Azure has released some updates which make things more confused.
https://azure.microsoft.com/en-us/updates/zone-behavior-change/
According to Azure/azure-powershell#12925, it seems Azure changes the network API in 2020-08-01 which azurerm is still at 2020-07-01. There could be some behavior changes in this area when azurerm is upgraded to 2020-08-01.

Azure Portal provides 5 options when creating an IP address in the Portal: No Zone, Zone Redundant, 1, 2, 3.

We understand the current behavior is Terraform will create a zone-redundant IP by default if we do not add the zones parameter. The bottom line we should allow the users to pass something to zones to be able to create a "No Zone" IP address even if we run it in the zone supported regions.

[windwindblow]

I think it could be resolved after #11627 is checked in.

[ghost]

This has been released in version 2.63.0 of the provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading. As an example:

provider "azurerm" {
    version = "~> 2.63.0"
}
# ... other configuration ...

[github-actions]

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