Fix for vscode-powershell issue 168.

Catch exceptions when calling ToString().

Author: rkeithhill

src/PowerShellEditorServices/Debugging/VariableDetails.cs

@@ -10,6 +10,7 @@
 using System.Linq;
 using System.Management.Automation;
 using System.Reflection;
+using Microsoft.PowerShell.EditorServices.Utility;
 
 namespace Microsoft.PowerShell.EditorServices
 {
@@ -159,44 +160,49 @@ private static string GetValueString(object value, bool isExpandable)
                             entry.Key,
                             GetValueString(entry.Value, GetIsExpandable(entry.Value)));
                 }
-                else if (value.ToString().Equals(objType.ToString()))
+                else
                 {
-                    // If the ToString() matches the type name, then display the type 
-                    // name in PowerShell format.
-                    string shortTypeName = objType.Name;
+                    string valueToString = value.SafeToString();
 
-                    // For arrays and ICollection, display the number of contained items.
-                    if (value is Array)
+                    if (valueToString.Equals(objType.ToString()))
                     {
-                        var arr = value as Array;
-                        if (arr.Rank == 1)
+                        // If the ToString() matches the type name, then display the type 
+                        // name in PowerShell format.
+                        string shortTypeName = objType.Name;
+
+                        // For arrays and ICollection, display the number of contained items.
+                        if (value is Array)
                         {
-                            shortTypeName = InsertDimensionSize(shortTypeName, arr.Length);
+                            var arr = value as Array;
+                            if (arr.Rank == 1)
+                            {
+                                shortTypeName = InsertDimensionSize(shortTypeName, arr.Length);
+                            }
                         }
+                        else if (value is ICollection)
+                        {
+                            var collection = (ICollection)value;
+                            shortTypeName = InsertDimensionSize(shortTypeName, collection.Count);
+                        }
+
+                        valueString = "[" + shortTypeName + "]";
                     }
-                    else if (value is ICollection)
+                    else
                     {
-                        var collection = (ICollection)value;
-                        shortTypeName = InsertDimensionSize(shortTypeName, collection.Count);
+                        valueString = valueToString;
                     }
-
-                    valueString = "[" + shortTypeName + "]";
-                }
-                else
-                {
-                    valueString = value.ToString();
                 }
             }
             else
             {
-                // ToString() output is not the typename, so display that as this object's value
+                // Value is a scalar (not expandable). If it's a string, display it directly otherwise use SafeToString()
                 if (value is string)
                 {
                     valueString = "\"" + value + "\"";
                 }
                 else
                 {
-                    valueString = value.ToString();
+                    valueString = value.SafeToString();
                 }
             }
 

src/PowerShellEditorServices/PowerShellEditorServices.csproj

@@ -120,6 +120,7 @@
     <Compile Include="Utility\AsyncLock.cs" />
     <Compile Include="Utility\AsyncQueue.cs" />
     <Compile Include="Utility\AsyncContext.cs" />
+    <Compile Include="Utility\Extensions.cs" />
     <Compile Include="Utility\Logger.cs" />
     <Compile Include="Utility\ThreadSynchronizationContext.cs" />
     <Compile Include="Utility\Validate.cs" />

src/PowerShellEditorServices/Utility/Extensions.cs

@@ -0,0 +1,34 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using System;
+
+namespace Microsoft.PowerShell.EditorServices.Utility
+{
+    internal static class ObjectExtensions
+    {
+        /// <summary>
+        /// Extension to evaluate an object's ToString() method in an exception safe way. This will
+        /// extension method will not throw.
+        /// </summary>
+        /// <param name="obj">The object on which to call ToString()</param>
+        /// <returns>The ToString() return value or a suitable error message is that throws.</returns>
+        public static string SafeToString(this object obj)
+        {
+            string str;
+
+            try
+            {
+                str = obj.ToString();
+            }
+            catch (Exception ex)
+            {
+                str = $"<Error converting poperty value to string - {ex.Message}>";
+            }
+
+            return str;
+        }
+    }
+}