From fcf3130ff6f40b0160f26b093e665a6de4e49597 Mon Sep 17 00:00:00 2001
From: PaddiM8 <hi@bakk.dev>
Date: Sun, 17 Nov 2024 22:01:55 +0100
Subject: [PATCH] Catch exceptions from lazily evaluated code when stringifying
 evaluation result for REPL

---
 src/ShellSession.cs                           | 30 +++++++++++++++++--
 src/Std/DataTypes/RuntimeList.cs              |  2 +-
 .../RuntimeObjectJsonConverter.cs             |  8 ++---
 src/Vm/InstructionExecutor.cs                 | 10 ++++++-
 4 files changed, 41 insertions(+), 9 deletions(-)

diff --git a/src/ShellSession.cs b/src/ShellSession.cs
index 8918a674..c09e4472 100644
--- a/src/ShellSession.cs
+++ b/src/ShellSession.cs
@@ -7,6 +7,8 @@
 using System.Reflection.Metadata.Ecma335;
 using System.Text;
 using Elk.Analysis;
+using Elk.Exceptions;
+using Elk.Lexing;
 using Elk.Parsing;
 using Elk.Scoping;
 using Elk.Std.DataTypes;
@@ -126,9 +128,11 @@ public void RunCommand(
         }
         else
         {
-            resultBuilder.AppendLine(
-                evaluationResult.Value.ToString() ?? ""
-            );
+            var evaluationResultValue = GetEvaluationResultValue(evaluationResult);
+            if (evaluationResultValue.isError)
+                textWriter = Console.Error;
+
+            resultBuilder.AppendLine(evaluationResultValue.value);
         }
 
         if (!printReturnedValue && !evaluationResult.Diagnostics.Any())
@@ -151,6 +155,26 @@ public void RunCommand(
         Console.ResetColor();
     }
 
+    private (string value, bool isError) GetEvaluationResultValue(EvaluationResult evaluationResult)
+    {
+        try
+        {
+            var value = evaluationResult.Value?.ToString() ?? "";
+
+            return (value, isError: false);
+        }
+        catch (RuntimeException ex)
+        {
+            var diagnostic = new DiagnosticMessage(ex.Message, ex.StartPosition ?? TextPos.Default, ex.EndPosition ?? TextPos.Default)
+            {
+                StackTrace = ex.ElkStackTrace,
+            };
+            var value = diagnostic.ToString(includePosition: false).Trim();
+
+            return (value, isError: true);
+        }
+    }
+
     public void RunFile(string filePath, IEnumerable<string>? arguments)
     {
         arguments ??= new List<string>();
diff --git a/src/Std/DataTypes/RuntimeList.cs b/src/Std/DataTypes/RuntimeList.cs
index b634f69a..d83830da 100644
--- a/src/Std/DataTypes/RuntimeList.cs
+++ b/src/Std/DataTypes/RuntimeList.cs
@@ -97,7 +97,7 @@ public override string ToString()
         var totalIndentationLength = 3 * Values.Count;
 
         return json.Length - totalIndentationLength < lineLimit
-            ? $"[{string.Join(", ", Values.Select(x => x.ToDisplayString()))}]"
+            ? $"[{string.Join(", ", Values.Select(x => x?.ToDisplayString()))}]"
             : json;
     }
 }
\ No newline at end of file
diff --git a/src/Std/Serialization/RuntimeObjectJsonConverter.cs b/src/Std/Serialization/RuntimeObjectJsonConverter.cs
index 2dbb197d..af68cc7a 100644
--- a/src/Std/Serialization/RuntimeObjectJsonConverter.cs
+++ b/src/Std/Serialization/RuntimeObjectJsonConverter.cs
@@ -73,11 +73,11 @@ private JValue BuildValue(RuntimeObject value)
     {
         return value switch
         {
-            RuntimeBoolean boolean => new(boolean.IsTrue),
-            RuntimeFloat floatValue => new(floatValue.Value),
-            RuntimeInteger integerValue => new(integerValue.Value),
+            RuntimeBoolean boolean => new JValue(boolean.IsTrue),
+            RuntimeFloat floatValue => new JValue(floatValue.Value),
+            RuntimeInteger integerValue => new JValue(integerValue.Value),
             RuntimeNil => JValue.CreateNull(),
-            _ => new(value.ToString() ?? ""),
+            _ => new JValue(value?.ToString() ?? ""),
         };
     }
 
diff --git a/src/Vm/InstructionExecutor.cs b/src/Vm/InstructionExecutor.cs
index f7eb346c..74689207 100644
--- a/src/Vm/InstructionExecutor.cs
+++ b/src/Vm/InstructionExecutor.cs
@@ -190,12 +190,20 @@ private void ExecuteCurrentPage()
                     throw;
 
                 var exceptionFrame = _context.ExceptionStack.Pop();
-                while (_currentPage != exceptionFrame.Page)
+                while (_callStack.Any() && _currentPage != exceptionFrame.Page)
                 {
                     ex.ElkStackTrace.Add(CreateTrace(_currentPage.Name));
                     PopFrame();
                 }
 
+                // If the current context doesn't have the exception frame,
+                // add it back and throw, to let the parent context handle it
+                if (_currentPage != exceptionFrame.Page)
+                {
+                    _context.ExceptionStack.Push(exceptionFrame);
+                    throw;
+                }
+
                 while (_stack.Count > exceptionFrame.StackSize)
                     _stack.PopObject();