Fix ArgumentOutOfRangeException when throw is used

Co-authored-by: Andy Schwartzmeyer <andrew@schwartzmeyer.com>

Author: JustinGrote

src/PowerShellEditorServices/Services/PowerShell/Utility/ErrorRecordExtensions.cs

@@ -34,7 +34,7 @@ static ErrorRecordExtensions()
                 s_setWriteStreamProperty = Expression.Lambda<Action<PSObject>>(
                     Expression.Call(
                         errorObjectParameter,
-                        writeStreamProperty.GetSetMethod(),
+                        writeStreamProperty.GetSetMethod(nonPublic: true),
                         Expression.Constant(errorStreamType)),
                     errorObjectParameter)
                     .Compile();

src/PowerShellEditorServices/Utility/PSCommandExtensions.cs

@@ -61,10 +61,13 @@ public static PSCommand AddDebugOutputCommand(this PSCommand psCommand)
 
         public static PSCommand MergePipelineResults(this PSCommand psCommand)
         {
-            // We need to do merge errors and output before rendering with an Out- cmdlet
-            Command lastCommand = psCommand.Commands[psCommand.Commands.Count - 1];
-            lastCommand.MergeMyResults(PipelineResultTypes.Error, PipelineResultTypes.Output);
-            lastCommand.MergeMyResults(PipelineResultTypes.Information, PipelineResultTypes.Output);
+            if (psCommand.Commands.Count > 0)
+            {
+                // We need to do merge errors and output before rendering with an Out- cmdlet
+                Command lastCommand = psCommand.Commands[psCommand.Commands.Count - 1];
+                lastCommand.MergeMyResults(PipelineResultTypes.Error, PipelineResultTypes.Output);
+                lastCommand.MergeMyResults(PipelineResultTypes.Information, PipelineResultTypes.Output);
+            }
             return psCommand;
         }
 

test/PowerShellEditorServices.Test/Session/PsesInternalHostTests.cs

@@ -46,14 +46,10 @@ public async Task CanExecutePSCommand()
         [Fact]
         public async Task CanHandleThrow()
         {
-            // TODO: Fix this so it doesn't throw!
-            _ = await Assert.ThrowsAsync<ArgumentOutOfRangeException>(() =>
-            {
-                return psesHost.ExecutePSCommandAsync(
-                    new PSCommand().AddScript("throw"),
-                    CancellationToken.None,
-                    new PowerShellExecutionOptions { ThrowOnError = false });
-            }).ConfigureAwait(true);
+            await psesHost.ExecutePSCommandAsync(
+                new PSCommand().AddScript("throw"),
+                CancellationToken.None,
+                new PowerShellExecutionOptions { ThrowOnError = false }).ConfigureAwait(true);
         }
 
         [Trait("Category", "PsesInternalHost")]