Set-AzVMOperatingSystem fix null reference when credential is not pro…

…vided (#25624)

* dev and test and changelog and help doc

* Update VirtualMachineTests.ps1, remove passwords

* Update VirtualMachineTests.ps1

* test and simplify code

* Update VirtualMachineTests.ps1

* rerecord old test for password removal

* Update TestVMSetAzOSCredentialNullRef.json, remove auto password

src/Compute/Compute.Test/ScenarioTests/VirtualMachineTests.cs

@@ -661,5 +661,12 @@ public void TestAddVMDataDisk()
         {
             TestRunner.RunTestScript("Test-AddVMDataDisk");
         }
+
+        [Fact]
+        [Trait(Category.AcceptanceType, Category.CheckIn)]
+        public void TestVMSetAzOSCredentialNullRef()
+        {
+            TestRunner.RunTestScript("Test-VMSetAzOSCredentialNullRef");
+        }
     }
 }

src/Compute/Compute.Test/ScenarioTests/VirtualMachineTests.ps1

@@ -5295,8 +5295,8 @@ function Test-VirtualMachineEnableAutoUpdate
         $computerName = "v" + $rgname;
 
         # VM Credential
-        $user = "usertest";
-        $password = "*****";
+        $user = Get-ComputeTestResourceName;
+        $password = Get-PasswordForVM;
         $securePassword = ConvertTo-SecureString $password -AsPlainText -Force;
         $cred = New-Object System.Management.Automation.PSCredential ($user, $securePassword);
 
@@ -6255,7 +6255,7 @@ function Test-ManualConfidentialVMSetAzVmOsDiskDesIdDiskWithVMGuest
         $secureEncryptGuestState = 'DiskWithVMGuestState';
         $vmSecurityType = "ConfidentialVM";
         $user = "admin01";
-        $password;
+        $password = $PLACEHOLDER;
         $securePassword = $password | ConvertTo-SecureString -AsPlainText -Force;
         $cred = New-Object System.Management.Automation.PSCredential ($user, $securePassword);
 
@@ -6583,7 +6583,8 @@ function Test-ConfVMSetAzDiskEncryptionSetConfig
         $desName= "des" + $rgname;
 
         # Creating a VM using simple parameterset
-        $securePassword | ConvertTo-SecureString -AsPlainText -Force;
+        $password = "*****";
+        $securePassword = $password | ConvertTo-SecureString -AsPlainText -Force;
         $user = "admin01";
         $cred = New-Object System.Management.Automation.PSCredential ($user, $securePassword);
 
@@ -7542,3 +7543,69 @@ function Test-AddVMDataDisk
     # Validate
     Assert-AreEqual $vmConfig.StorageProfile.DataDisks[0].SourceResource.id "testSourceResourceId"
 }
+
+<#
+.SYNOPSIS
+Test Set-AzVMOperatingSystem does not have a null ref exception.
+The ComputerName is an expected required parameter. 
+#>
+function Test-VMSetAzOSCredentialNullRef
+{
+    # Setup
+    $rgname = Get-ComputeTestResourceName;
+    $loc = "westus2";#Get-ComputeVMLocation;
+
+    try
+    {
+        New-AzResourceGroup -Name $rgname -Location $loc -Force;
+        # SimpleParameterSet, no config, scenario.
+        # create credential
+        $password = Get-PasswordForVM;
+        $securePassword = $password | ConvertTo-SecureString -AsPlainText -Force;
+        $user = Get-ComputeTestResourceName;
+        $cred = New-Object System.Management.Automation.PSCredential ($user, $securePassword);
+
+        # DefaultParameterSet with VMConfig scenario
+        $domainNameLabel = "d2" + $rgname;
+        $vmsize = 'Standard_D4s_v3';
+        $vmname = 'v' + $rgname;
+        $vnetname = "vn" + $rgname;
+        $vnetAddress = "10.0.0.0/16";
+        $subnetname = "slb" + $rgname;
+        $subnetAddress = "10.0.2.0/24";
+        $OSDiskName = $vmname + "d";
+        $NICName = $vmname+ "n";
+        $NSGName = $vmname + "nsg";
+
+        # Creating a VM using Default parameterset
+        $frontendSubnet = New-AzVirtualNetworkSubnetConfig -Name $subnetname -AddressPrefix $subnetAddress;
+
+        $vnet = New-AzVirtualNetwork -Name $vnetname -ResourceGroupName $rgname -Location $loc -AddressPrefix $vnetAddress -Subnet $frontendSubnet;
+
+        $nsgRuleRDP = New-AzNetworkSecurityRuleConfig -Name RDP  -Protocol Tcp  -Direction Inbound -Priority 1001 -SourceAddressPrefix * -SourcePortRange * -DestinationAddressPrefix * -DestinationPortRange 3389 -Access Allow;
+        $nsg = New-AzNetworkSecurityGroup -ResourceGroupName $rgname -Location $loc -Name $NSGName  -SecurityRules $nsgRuleRDP;
+        $nic = New-AzNetworkInterface -Name $NICName -ResourceGroupName $rgname -Location $loc -SubnetId $vnet.Subnets[0].Id -NetworkSecurityGroupId $nsg.Id -EnableAcceleratedNetworking;
+
+        # VM
+        $vmConfig = New-AzVMConfig -VMName $vmname -VMSize $vmsize;
+        $vmConfig = Set-AzVMOperatingSystem -VM $vmConfig -Windows -ComputerName $vmname;
+        $vmConfig = Add-AzVMNetworkInterface -VM $vmConfig -Id $nic.Id;
+
+        # Verify a VM needs the ComputerName. 
+        Assert-ThrowsContains {New-AzVM -ResourceGroupName $rgname -Location $loc -VM $vmConfig; } "Required parameter"
+
+        # Verify the VM is created successfully. 
+        $vmConfig = New-AzVMConfig -VMName $vmname -VMSize $vmsize;
+        $vmConfig = Set-AzVMOperatingSystem -VM $vmConfig -Windows -ComputerName $vmname -Credential $cred;
+        $vmConfig = Add-AzVMNetworkInterface -VM $vmConfig -Id $nic.Id;
+        New-AzVM -ResourceGroupName $rgname -Location $loc -VM $vmconfig;
+
+        $vm = Get-AzVM -ResourceGroupName $rgname -Name $vmname;
+        Assert-NotNull $vm;
+    }
+    finally
+    {
+        # Cleanup
+        Clean-ResourceGroup $rgname;
+    }
+}