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)
@@ -77,10 +73,12 @@ public bool IsDscResourcePath(string scriptPath)
                         StringComparison.CurrentCultureIgnoreCase));
         }
 
+        private const string prevProgressPreferenceVariable = $"$global:{DebugService.PsesGlobalVariableNamePrefix}prevProgressPreference";
+
         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 +90,13 @@ 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 +108,36 @@ await psesHost.ExecutePSCommandAsync<PSModuleInfo>(
 
             if (isDscInstalled.Value)
             {
+                // Silence the progress output from Get-DscResource.
+                PSCommand setProgressPreferenceCommand = new PSCommand()
+                    .AddScript($"{prevProgressPreferenceVariable} = $ProgressPreference")
+                    .AddStatement()
+                    .AddScript("$ProgressPreference = 'SilentlyContinue'");
+
+                await executionService.ExecutePSCommandAsync(
+                    setProgressPreferenceCommand, CancellationToken.None).ConfigureAwait(false);
+
                 PSCommand psCommand = new PSCommand()
                     .AddCommand("Get-DscResource")
                     .AddCommand("Select-Object")
                     .AddParameter("ExpandProperty", "ParentPath");
 
                 IReadOnlyList<string> resourcePaths =
-                    await psesHost.ExecutePSCommandAsync<string>(
+                    await executionService.ExecutePSCommandAsync<string>(
                         psCommand,
                         CancellationToken.None,
                         new PowerShellExecutionOptions { ThrowOnError = false }
                     ).ConfigureAwait(false);
 
                 logger.LogTrace($"DSC resources found: {resourcePaths.Count}");
+
+                // Restore previous progress preference.
+                PSCommand restoreProgressPreferenceCommand = new PSCommand()
+                    .AddScript($"$ProgressPreference = {prevProgressPreferenceVariable}");
+
+                await executionService.ExecutePSCommandAsync(
+                    restoreProgressPreferenceCommand, CancellationToken.None).ConfigureAwait(false);
+
                 return new DscBreakpointCapability
                 {
                     dscResourceRootPaths = resourcePaths.ToArray()