From 3dd91d5521304ec72eabf383179b5f5aa26bec4a Mon Sep 17 00:00:00 2001
From: Andy Jordan <2226434+andyleejordan@users.noreply.github.com>
Date: Fri, 10 Nov 2023 15:21:36 -0800
Subject: [PATCH] When the built-in `$null` was watched its value was incorrect

This fixes the evaluation of `$null` itself and variables that don't
exist such that they display correctly in the watched variables pane of
the debugger. As noted, the issue was that we were doing a string join
even for a single (potentially null) value.

This also fixes the excess quotes bug around a single value.
---
 .../Services/DebugAdapter/DebugService.cs            | 12 ++++++++----
 .../DebugAdapter/Handlers/DebugEvaluateHandler.cs    |  1 +
 .../Debugging/DebugServiceTests.cs                   |  2 +-
 3 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/src/PowerShellEditorServices/Services/DebugAdapter/DebugService.cs b/src/PowerShellEditorServices/Services/DebugAdapter/DebugService.cs
index 43c54c17a..90faceda4 100644
--- a/src/PowerShellEditorServices/Services/DebugAdapter/DebugService.cs
+++ b/src/PowerShellEditorServices/Services/DebugAdapter/DebugService.cs
@@ -527,11 +527,15 @@ public async Task<VariableDetails> EvaluateExpressionAsync(
                 return null;
             }
 
-            // If we didn't write output,
-            // return a VariableDetails instance.
+            // If we didn't write output, return a VariableDetails instance.
             return new VariableDetails(
-                    expressionString,
-                    string.Join(Environment.NewLine, results));
+                expressionString,
+                // If there's only one result, we want its raw value (especially if it's null). For
+                // a collection, since we're displaying these, we want to concatenante them.
+                // However, doing that for one result caused null to be turned into an empty string.
+                results.Count == 1
+                    ? results[0]
+                    : string.Join(Environment.NewLine, results));
         }
 
         /// <summary>
diff --git a/src/PowerShellEditorServices/Services/DebugAdapter/Handlers/DebugEvaluateHandler.cs b/src/PowerShellEditorServices/Services/DebugAdapter/Handlers/DebugEvaluateHandler.cs
index cd91809fd..78c55c1f1 100644
--- a/src/PowerShellEditorServices/Services/DebugAdapter/Handlers/DebugEvaluateHandler.cs
+++ b/src/PowerShellEditorServices/Services/DebugAdapter/Handlers/DebugEvaluateHandler.cs
@@ -22,6 +22,7 @@ internal class DebugEvaluateHandler : IEvaluateHandler
         private readonly IInternalPowerShellExecutionService _executionService;
         private readonly DebugService _debugService;
 
+        // AKA Watch Variables
         public DebugEvaluateHandler(
             ILoggerFactory factory,
             IPowerShellDebugContext debugContext,
diff --git a/test/PowerShellEditorServices.Test/Debugging/DebugServiceTests.cs b/test/PowerShellEditorServices.Test/Debugging/DebugServiceTests.cs
index b6a1aa48d..30b020c30 100644
--- a/test/PowerShellEditorServices.Test/Debugging/DebugServiceTests.cs
+++ b/test/PowerShellEditorServices.Test/Debugging/DebugServiceTests.cs
@@ -529,7 +529,7 @@ await debugService.SetCommandBreakpointsAsync(
             AssertDebuggerStopped(testScript.FilePath, 11);
 
             VariableDetails prompt = await debugService.EvaluateExpressionAsync("prompt", false, CancellationToken.None);
-            Assert.Equal("\"True > \"", prompt.ValueString);
+            Assert.Equal("True > ", prompt.ValueString);
         }
 
         [SkippableFact]