Silence progress output of Get-DscResource (take two)

It wasn't the module import that was being noisy but the next command.
It sure looked like the last commit "fixed" it in testing because the
output was certainly silenced...but that was actually due to the side
effect of having added an `AddScript` to the `PSCommand` causing it to
no longer return the imported module at all. Without that return value,
the noisy code wasn't executing either. Now the progress preference is
saved, set to silent, `Get-DscResource` is run (silently) and then the
preference is restored. Double-checked in the debugger.

Author: andyleejordan

src/PowerShellEditorServices/Services/PowerShell/Debugging/DscBreakpointCapability.cs

@@ -10,7 +10,6 @@
 using Microsoft.Extensions.Logging;
 using Microsoft.PowerShell.EditorServices.Services.DebugAdapter;
 using Microsoft.PowerShell.EditorServices.Services.PowerShell.Execution;
-using Microsoft.PowerShell.EditorServices.Services.PowerShell.Host;
 using Microsoft.PowerShell.EditorServices.Services.PowerShell.Runspace;
 
 namespace Microsoft.PowerShell.EditorServices.Services.PowerShell.Debugging
@@ -54,10 +53,7 @@ public async Task<IReadOnlyList<BreakpointDetails>> SetLineBreakpointsAsync(
                     ? $"Enable-DscDebug -Breakpoint {hashtableString}"
                     : "Disable-DscDebug");
 
-            await executionService.ExecutePSCommandAsync(
-                dscCommand,
-                CancellationToken.None)
-                .ConfigureAwait(false);
+            await executionService.ExecutePSCommandAsync(dscCommand, CancellationToken.None).ConfigureAwait(false);
 
             // Verify all the breakpoints and return them
             foreach (BreakpointDetails breakpoint in breakpoints)
@@ -80,7 +76,7 @@ public bool IsDscResourcePath(string scriptPath)
         public static async Task<DscBreakpointCapability> GetDscCapabilityAsync(
             ILogger logger,
             IRunspaceInfo currentRunspace,
-            PsesInternalHost psesHost)
+            IInternalPowerShellExecutionService executionService)
         {
             // DSC support is enabled only for Windows PowerShell.
             if ((currentRunspace.PowerShellVersionDetails.Version.Major >= 6) &&
@@ -92,16 +88,13 @@ public static async Task<DscBreakpointCapability> GetDscCapabilityAsync(
             if (!isDscInstalled.HasValue)
             {
                 PSCommand psCommand = new PSCommand()
-                    .AddScript($"$global:{DebugService.PsesGlobalVariableNamePrefix}prevProgressPreference = $ProgressPreference")
-                    .AddScript("$ProgressPreference = 'SilentlyContinue'")
                     .AddCommand(@"Microsoft.PowerShell.Core\Import-Module")
                     .AddParameter("Name", "PSDesiredStateConfiguration")
                     .AddParameter("PassThru")
-                    .AddParameter("ErrorAction", ActionPreference.Ignore)
-                    .AddScript($"$ProgressPreference = $global:{DebugService.PsesGlobalVariableNamePrefix}prevProgressPreference");
+                    .AddParameter("ErrorAction", ActionPreference.Ignore);
 
                 IReadOnlyList<PSModuleInfo> dscModule =
-                    await psesHost.ExecutePSCommandAsync<PSModuleInfo>(
+                    await executionService.ExecutePSCommandAsync<PSModuleInfo>(
                         psCommand,
                         CancellationToken.None,
                         new PowerShellExecutionOptions { ThrowOnError = false })
@@ -113,19 +106,29 @@ await psesHost.ExecutePSCommandAsync<PSModuleInfo>(
 
             if (isDscInstalled.Value)
             {
-                PSCommand psCommand = new PSCommand()
-                    .AddCommand("Get-DscResource")
-                    .AddCommand("Select-Object")
-                    .AddParameter("ExpandProperty", "ParentPath");
+                // Note that __psEditorServices_ is DebugService.PsesGlobalVariableNamePrefix but
+                // it's notoriously difficult to interpolate it in this script, which has to be a
+                // single script to guarantee everything is run at once.
+                PSCommand psCommand = new PSCommand().AddScript(
+                """
+                try {
+                    $global:__psEditorServices_prevProgressPreference = $ProgressPreference
+                    $global:ProgressPreference = 'SilentlyContinue'
+                    return Get-DscResource | Select-Object -ExpandProperty ParentPath
+                } finally {
+                    $ProgressPreference = $global:__psEditorServices_prevProgressPreference
+                }
+                """);
 
                 IReadOnlyList<string> resourcePaths =
-                    await psesHost.ExecutePSCommandAsync<string>(
+                    await executionService.ExecutePSCommandAsync<string>(
                         psCommand,
                         CancellationToken.None,
                         new PowerShellExecutionOptions { ThrowOnError = false }
                     ).ConfigureAwait(false);
 
                 logger.LogTrace($"DSC resources found: {resourcePaths.Count}");
+
                 return new DscBreakpointCapability
                 {
                     dscResourceRootPaths = resourcePaths.ToArray()