bug fix for Set-AzVmBootDisagnostic (#16011)

* bug fix

* add changelog

Author: grizzlytheodore

src/Compute/Compute/ChangeLog.md

@@ -20,6 +20,7 @@
 
 -->
 ## Upcoming Release
+* Update Set-AzVmBootDiagnostic to default to managed storage account if not provided.
 * Update Compute .NET SDK package reference to version 49.1.0
 * Fixed a bug in `Get-AzVM` that caused incorrect power status output.
 

src/Compute/Compute/VirtualMachine/Config/SetAzureVMBootDiagnosticsCommand.cs

@@ -56,7 +56,6 @@ public class SetAzureVMBootDiagnosticsCommand : Microsoft.Azure.Commands.Resourc
         public SwitchParameter Disable { get; set; }
 
         [Parameter(
-            Mandatory = true,
             Position = 2,
             ParameterSetName = EnableParameterSet,
             ValueFromPipelineByPropertyName = true,
@@ -86,14 +85,7 @@ public override void ExecuteCmdlet()
 
             if (this.Enable.IsPresent)
             {
-                if (string.IsNullOrEmpty(this.StorageAccountName))
-                {
-                    if (diagnosticsProfile.BootDiagnostics.StorageUri == null)
-                    {
-                        ThrowNoStorageAccount();
-                    }
-                }
-                else
+                if (!string.IsNullOrEmpty(this.StorageAccountName))
                 {
                     var storageClient = AzureSession.Instance.ClientFactory.CreateArmClient<StorageManagementClient>(
                         DefaultProfile.DefaultContext, AzureEnvironment.Endpoint.ResourceManager);

src/Compute/Compute/help/Set-AzVMBootDiagnostic.md

@@ -15,7 +15,7 @@ Modifies boot diagnostics properties of a virtual machine.
 
 ### EnableBootDiagnostics
 ```
-Set-AzVMBootDiagnostic [-VM] <PSVirtualMachine> [-Enable] [-ResourceGroupName] <String>
+Set-AzVMBootDiagnostic [-VM] <PSVirtualMachine> [-Enable] [[-ResourceGroupName] <String>]
  [[-StorageAccountName] <String>] [-DefaultProfile <IAzureContextContainer>] [<CommonParameters>]
 ```
 
@@ -34,7 +34,7 @@ The **Set-AzVMBootDiagnostic** cmdlet modifies boot diagnostics properties of a
 ```
 PS C:\> $VM = Get-AzVM -ResourceGroupName "ResourceGroup11" -Name "ContosoVM07"
 PS C:\> Set-AzVMBootDiagnostic -VM $VM -Enable -ResourceGroupName "ResourceGroup11" -StorageAccountName "DiagnosticStorage"
-PS C:\> Update-AzVM -VM $VM
+PS C:\> Update-AzVM -VM $VM -ResourceGroupName "ResourceGroup11"
 ```
 
 The first command gets the virtual machine named ContosoVM07 by using **Get-AzVM**.
@@ -97,15 +97,15 @@ Type: System.String
 Parameter Sets: EnableBootDiagnostics
 Aliases:
 
-Required: True
+Required: False
 Position: 2
 Default value: None
 Accept pipeline input: True (ByPropertyName)
 Accept wildcard characters: False
 ```
 
 ### -StorageAccountName
-Specifies the name of the storage account in which to save boot diagnostics data.
+Specifies the name of the storage account in which to save boot diagnostics data. If not provided, it will look for a StorageUri in the BootDiagnostic Profile in the PSVirtualMachine object provided in the '-VM' parameter. If StorageUri is null, it will default to used a managed storage account. 
 
 ```yaml
 Type: System.String