[Synapse] - fix workspace package null check issue (Azure#15847)

* [Synapse] - fix workspace package null check issue

* Fix null check for library requirements

* update changelog

Co-authored-by: Dongwei Wang <dongwwa@microsoft.com>

Author: idear1203

src/Synapse/Synapse/ChangeLog.md

@@ -18,6 +18,7 @@
         - Additional information about change #1
 -->
 ## Upcoming Release
+* Fixed the issue when `Update-AzSynapseSparkPool` is used with workspace package
 
 ## Version 0.15.0
 * Added support for Synapse Managed Private Endpoint

src/Synapse/Synapse/Commands/ManagementCommands/SparkPool/UpdateAzureSynapseSparkPool.cs

@@ -222,7 +222,7 @@ public override void ExecuteCmdlet()
             {
                 if (this.PackageAction == SynapseConstants.PackageActionType.Add)
                 {
-                    if (existingSparkPool == null)
+                    if (existingSparkPool.CustomLibraries == null)
                     {
                         existingSparkPool.CustomLibraries = new List<LibraryInfo>();
                     }
@@ -251,6 +251,11 @@ public override void ExecuteCmdlet()
 
         private LibraryRequirements CreateLibraryRequirements()
         {
+            if (string.IsNullOrEmpty(LibraryRequirementsFilePath))
+            {
+                return null;
+            }
+
             var powerShellDestinationPath = SessionState.Path.GetUnresolvedProviderPathFromPSPath(LibraryRequirementsFilePath);
 
             return new LibraryRequirements

src/Synapse/Synapse/help/Update-AzSynapseSparkPool.md

@@ -122,15 +122,23 @@ PS C:\> $packages = Get-AzSynapseWorkspacePackage -WorkspaceName ContosoWorkspac
 PS C:\> Update-AzSynapseSparkPool -WorkspaceName ContosoWorkspace -Name ContosoSparkPool -PackageAction Add -Package $packages
 ```
 
-The first command retrieves workspace packages. The second command links these workspaces packages to an Apache Spark pool in Azure Synapse Analytics.
+The first command retrieves workspace packages. The second command links these workspace packages to an Apache Spark pool in Azure Synapse Analytics.
 
 ### Example 10
 ```powershell
 PS C:\> $package = Get-AzSynapseWorkspacePackage -WorkspaceName ContosoWorkspace -Name ContosoPackage
 PS C:\> Update-AzSynapseSparkPool -WorkspaceName ContosoWorkspace -Name ContosoSparkPool -PackageAction Remove -Package $package
 ```
 
-The first command retrieves workspace packages named ContosoPackage. The second command removes the workspaces package from an Apache Spark pool in Azure Synapse Analytics.
+The first command retrieves workspace packages named ContosoPackage. The second command removes the workspace package from an Apache Spark pool in Azure Synapse Analytics.
+
+### Example 11
+```powershell
+PS C:\> $pool = Get-AzSynapseSparkPool -ResourceGroupName ContosoResourceGroup -WorkspaceName ContosoWorkspace -Name ContosoSparkPool
+PS C:\> $pool | Update-AzSynapseSparkPool -PackageAction Remove -Package $pool.WorkspacePackages
+```
+
+The first command retrieves an Apache Spark pool in Azure Synapse Analytics. The second command removes all workspace packages that are linked to that Apache Spark pool.
 
 ## PARAMETERS