windows_virtual_machine_scale_set: Allow updating license_type without recreation

azurerm/internal/services/compute/windows_virtual_machine_scale_set_other_resource_test.go

@@ -730,6 +730,42 @@ func TestAccWindowsVirtualMachineScaleSet_otherHealthProbeUpdate(t *testing.T) {
 	})
 }
 
+func TestAccWindowsVirtualMachineScaleSet_otherLicenseTypeUpdated(t *testing.T) {
+	data := acceptance.BuildTestData(t, "azurerm_windows_virtual_machine_scale_set", "test")
+	r := WindowsVirtualMachineScaleSetResource{}
+
+	data.ResourceTest(t, r, []resource.TestStep{
+		{
+			Config: r.otherLicenseTypeDefault(data),
+			Check: resource.ComposeTestCheckFunc(
+				check.That(data.ResourceName).ExistsInAzure(r),
+			),
+		},
+		data.ImportStep(
+			"admin_password",
+		),
+		{
+			Config: r.otherLicenseType(data, "Windows_Client"),
+			Check: resource.ComposeTestCheckFunc(
+				check.That(data.ResourceName).ExistsInAzure(r),
+				check.That(data.ResourceName).Key("license_type").HasValue("Windows_Client"),
+			),
+		},
+		data.ImportStep(
+			"admin_password",
+		),
+		{
+			Config: r.otherLicenseTypeDefault(data),
+			Check: resource.ComposeTestCheckFunc(
+				check.That(data.ResourceName).ExistsInAzure(r),
+			),
+		},
+		data.ImportStep(
+			"admin_password",
+		),
+	})
+}
+
 func (WindowsVirtualMachineScaleSetResource) otherAdditionalUnattendContent(data acceptance.TestData) string {
 	template := WindowsVirtualMachineScaleSetResource{}.template(data)
 	return fmt.Sprintf(`
@@ -2788,3 +2824,82 @@ resource "azurerm_windows_virtual_machine_scale_set" "test" {
 }
 `, r.template(data), data.RandomInteger)
 }
+
+func (r WindowsVirtualMachineScaleSetResource) otherLicenseTypeDefault(data acceptance.TestData) string {
+	return fmt.Sprintf(`
+%s
+
+resource "azurerm_windows_virtual_machine_scale_set" "test" {
+  name                = local.vm_name
+  resource_group_name = azurerm_resource_group.test.name
+  location            = azurerm_resource_group.test.location
+  sku                 = "Standard_F2"
+  instances           = 1
+  admin_username      = "adminuser"
+  admin_password      = "P@ssword1234!"
+
+  source_image_reference {
+    publisher = "MicrosoftWindowsServer"
+    offer     = "WindowsServer"
+    sku       = "2019-Datacenter"
+    version   = "latest"
+  }
+
+  os_disk {
+    storage_account_type = "Standard_LRS"
+    caching              = "ReadWrite"
+  }
+
+  network_interface {
+    name    = "example"
+    primary = true
+
+    ip_configuration {
+      name      = "internal"
+      primary   = true
+      subnet_id = azurerm_subnet.test.id
+    }
+  }
+}
+`, r.template(data))
+}
+
+func (r WindowsVirtualMachineScaleSetResource) otherLicenseType(data acceptance.TestData, licenseType string) string {
+	return fmt.Sprintf(`
+%s
+
+resource "azurerm_windows_virtual_machine_scale_set" "test" {
+  name                = local.vm_name
+  resource_group_name = azurerm_resource_group.test.name
+  location            = azurerm_resource_group.test.location
+  sku                 = "Standard_F2"
+  instances           = 1
+  admin_username      = "adminuser"
+  admin_password      = "P@ssword1234!"
+  license_type        = %q
+
+  source_image_reference {
+    publisher = "MicrosoftWindowsServer"
+    offer     = "WindowsServer"
+    sku       = "2019-Datacenter"
+    version   = "latest"
+  }
+
+  os_disk {
+    storage_account_type = "Standard_LRS"
+    caching              = "ReadWrite"
+  }
+
+  network_interface {
+    name    = "example"
+    primary = true
+
+    ip_configuration {
+      name      = "internal"
+      primary   = true
+      subnet_id = azurerm_subnet.test.id
+    }
+  }
+}
+`, r.template(data), licenseType)
+}

azurerm/internal/services/compute/windows_virtual_machine_scale_set_resource.go

@@ -163,12 +163,18 @@ func resourceWindowsVirtualMachineScaleSet() *schema.Resource {
 			"license_type": {
 				Type:     schema.TypeString,
 				Optional: true,
-				ForceNew: true,
 				ValidateFunc: validation.StringInSlice([]string{
 					"None",
 					"Windows_Client",
 					"Windows_Server",
 				}, false),
+				DiffSuppressFunc: func(_, old, new string, _ *schema.ResourceData) bool {
+					if old == "None" && new == "" || old == "" && new == "None" {
+						return true
+					}
+
+					return false
+				},
 			},
 
 			"max_bid_price": {
@@ -809,6 +815,17 @@ func resourceWindowsVirtualMachineScaleSetUpdate(d *schema.ResourceData, meta in
 		}
 	}
 
+	if d.HasChange("license_type") {
+		license := d.Get("license_type").(string)
+		if license == "" {
+			// Only for create no specification is possible in the API. API does not allow empty string in update.
+			// So removing attribute license_type from Terraform configuration if it was set to value other than 'None' would lead to an endless loop in apply.
+			// To allow updating in this case set value explicitly to 'None'.
+			license = "None"
+		}
+		updateProps.VirtualMachineProfile.LicenseType = &license
+	}
+
 	if d.HasChange("automatic_instance_repair") {
 		automaticRepairsPolicyRaw := d.Get("automatic_instance_repair").([]interface{})
 		automaticRepairsPolicy := ExpandVirtualMachineScaleSetAutomaticRepairsPolicy(automaticRepairsPolicyRaw)

website/docs/r/windows_virtual_machine_scale_set.html.markdown

@@ -144,7 +144,7 @@ The following arguments are supported:
 
 * `identity` - (Optional) A `identity` block as defined below.
 
-* `license_type` - (Optional) Specifies the type of on-premise license (also known as [Azure Hybrid Use Benefit](https://docs.microsoft.com/azure/virtual-machines/virtual-machines-windows-hybrid-use-benefit-licensing)) which should be used for this Virtual Machine Scale Set. Possible values are `None`, `Windows_Client` and `Windows_Server`. Changing this forces a new resource to be created.
+* `license_type` - (Optional) Specifies the type of on-premise license (also known as [Azure Hybrid Use Benefit](https://docs.microsoft.com/azure/virtual-machines/virtual-machines-windows-hybrid-use-benefit-licensing)) which should be used for this Virtual Machine Scale Set. Possible values are `None`, `Windows_Client` and `Windows_Server`.
 
 * `max_bid_price` - (Optional) The maximum price you're willing to pay for each Virtual Machine in this Scale Set, in US Dollars; which must be greater than the current spot price. If this bid price falls below the current spot price the Virtual Machines in the Scale Set will be evicted using the `eviction_policy`. Defaults to `-1`, which means that each Virtual Machine in the Scale Set should not be evicted for price reasons.