Microsoft.RecoveryServices - confusing/incorrect error message

[sreallymatt]

API Spec link

https://github.com/Azure/azure-rest-api-specs/blob/main/specification/recoveryservicesbackup/resource-manager/Microsoft.RecoveryServices

API Spec version

2023-02-01

Question/Query

The API returns a confusing/incorrect error message when attempting to set an existing backup item's ProtectionState to BackupsSuspended.

Error message:

{
	"error": {
		"code": "UserErrorOperationDeniedOnImmutableItem",
		"message": "The Vault and Bakcup Item is in Immutable state where destructive operations are not supported. The Vault and Backup Item is immutable, hence operation is denied. Refer to the documentation to learn more: https://aka.ms/AB-ImmutableVaults-States "
	}
}

The error message above seems to imply that this operation was denied because the vault was in an immutable state, which it was not, interestingly enabling vault immutability and sending the request again responds with HTTP 202 and subsequent GET requests show this was applied to the backup item.

I encountered it in API version 2023-02-01 however the behaviour seems to be the same in the latest stable version (2024-10-01)

Example Request

PUT https://management.azure.com/subscriptions/<subscription ID>/resourceGroups/<resource group name>/providers/Microsoft.RecoveryServices/vaults/<vault name>/backupFabrics/<backup fabric name>/protectionContainers/<container name>/protectedItems/VM;<name>?api-version=2023-02-01

{
    "properties": {
        "protectedItemType": "Microsoft.Compute/virtualMachines",
        "protectionState": "BackupsSuspended",
        "sourceResourceId": "/subscriptions/<subscription ID>/resourceGroups/<resource group name>/providers/Microsoft.Compute/virtualMachines/<vm name>"
    }
}

Environment

No response