Write RuntimeExceptions to PSHostUserInterface

This change causes RuntimeExceptions thrown during
PowerShellContext.ExecuteCommand calls to be written to the host.
Previously these error messages were not being written so users did not
see error output for any commands using the "-ErrorAction Stop" parameter.

Author: daviwil

src/PowerShellEditorServices/Session/PowerShellContext.cs

@@ -6,6 +6,8 @@
 using Microsoft.PowerShell.EditorServices.Utility;
 using Nito.AsyncEx;
 using System;
+using System.Collections;
+using System.Globalization;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using System.Linq;
@@ -15,7 +17,6 @@
 
 namespace Microsoft.PowerShell.EditorServices
 {
-    using System.Collections;
     using System.Management.Automation;
     using System.Management.Automation.Host;
     using System.Management.Automation.Runspaces;
@@ -322,10 +323,12 @@ await Task.Factory.StartNew<IEnumerable<TResult>>(
                 }
                 catch (RuntimeException e)
                 {
-                    // TODO: Return an error
                     Logger.Write(
                         LogLevel.Error,
-                        "Exception occurred while attempting to execute command:\r\n\r\n" + e.ToString());
+                        "Runtime exception occurred while executing command:\r\n\r\n" + e.ToString());
+
+                    // Write the error to the host
+                    this.WriteExceptionToHost(e);
                 }
             }
 
@@ -522,6 +525,75 @@ private void OnSessionStateChanged(object sender, SessionStateChangedEventArgs e
 
         #region Private Methods
 
+        private void WriteExceptionToHost(Exception e)
+        {
+            const string ExceptionFormat =
+                "{0}\r\n{1}\r\n    + CategoryInfo          : {2}\r\n    + FullyQualifiedErrorId : {3}";
+
+            IContainsErrorRecord containsErrorRecord = e as IContainsErrorRecord;
+
+            if (containsErrorRecord == null || 
+                containsErrorRecord.ErrorRecord == null)
+            {
+                this.WriteError(e.Message, null, 0, 0);
+                return;
+            }
+
+            ErrorRecord errorRecord = containsErrorRecord.ErrorRecord;
+            if (errorRecord.InvocationInfo == null)
+            {
+                this.WriteError(errorRecord.ToString(), String.Empty, 0, 0);
+                return;
+            }
+
+            string errorRecordString = errorRecord.ToString();
+            if ((errorRecord.InvocationInfo.PositionMessage != null) &&
+                errorRecordString.IndexOf(errorRecord.InvocationInfo.PositionMessage, StringComparison.Ordinal) != -1)
+            {
+                this.WriteError(errorRecordString);
+                return;
+            }
+
+            string message = 
+                string.Format(
+                    CultureInfo.InvariantCulture,
+                    ExceptionFormat,
+                    errorRecord.ToString(),
+                    errorRecord.InvocationInfo.PositionMessage,
+                    errorRecord.CategoryInfo,
+                    errorRecord.FullyQualifiedErrorId);
+
+            this.WriteError(message);
+        }
+
+        private void WriteError(
+            string errorMessage,
+            string filePath,
+            int lineNumber,
+            int columnNumber)
+        {
+            const string ErrorLocationFormat = "At {0}:{1} char:{2}";
+
+            this.WriteError(
+                errorMessage +
+                Environment.NewLine +
+                string.Format(
+                    ErrorLocationFormat,
+                    String.IsNullOrEmpty(filePath) ? "line" : filePath,
+                    lineNumber,
+                    columnNumber));
+        }
+
+        private void WriteError(string errorMessage)
+        {
+            ((IConsoleHost)this).WriteOutput(
+                errorMessage,
+                true,
+                OutputType.Error,
+                ConsoleColor.Red,
+                ConsoleColor.Black);
+        }
+
         void powerShell_InvocationStateChanged(object sender, PSInvocationStateChangedEventArgs e)
         {
             SessionStateChangedEventArgs eventArgs = TranslateInvocationStateInfo(e.InvocationStateInfo);