pythonnet · filmor · Jan 29, 2021 · Jan 21, 2021 · Jan 21, 2021 · Jan 21, 2021
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -39,22 +39,23 @@ or the DLL must be loaded in advance. This must be done before calling any other
 
 ### Fixed
 
--    Fix incorrect dereference of wrapper object in `tp_repr`, which may result in a program crash
--    Fix incorrect dereference in params array handling
--    Fixes issue with function resolution when calling overloaded function with keyword arguments from python ([#1097][i1097])
--    Fix `object[]` parameters taking precedence when should not in overload resolution
--    Fixed a bug where all .NET class instances were considered Iterable
--    Fix incorrect choice of method to invoke when using keyword arguments.
--    Fix non-delegate types incorrectly appearing as callable.
--    Indexers can now be used with interface objects
--    Fixed a bug where indexers could not be used if they were inherited
--    Made it possible to use `__len__` also on `ICollection<>` interface objects
--    Fixed issue when calling PythonException.Format where another exception would be raise for unnormalized exceptions
--    Made it possible to call `ToString`, `GetHashCode`, and `GetType` on inteface objects
--    Fixed objects returned by enumerating `PyObject` being disposed too soon
--    Incorrectly using a non-generic type with type parameters now produces a helpful Python error instead of throwing NullReferenceException ([#1325][i1325])
--    `import` may now raise errors with more detail than "No module named X"
--    Providing an invalid type parameter to a generic type or method produces a helpful Python error
+-   Fix incorrect dereference of wrapper object in `tp_repr`, which may result in a program crash
+-   Fix incorrect dereference in params array handling
+-   Fixes issue with function resolution when calling overloaded function with keyword arguments from python ([#1097][i1097])
+-   Fix `object[]` parameters taking precedence when should not in overload resolution
+-   Fixed a bug where all .NET class instances were considered Iterable
+-   Fix incorrect choice of method to invoke when using keyword arguments.
+-   Fix non-delegate types incorrectly appearing as callable.
+-   Indexers can now be used with interface objects
+-   Fixed a bug where indexers could not be used if they were inherited
+-   Made it possible to use `__len__` also on `ICollection<>` interface objects
+-   Fixed issue when calling PythonException.Format where another exception would be raise for unnormalized exceptions
+-   Made it possible to call `ToString`, `GetHashCode`, and `GetType` on inteface objects
+-   Fixed objects returned by enumerating `PyObject` being disposed too soon
+-   Incorrectly using a non-generic type with type parameters now produces a helpful Python error instead of throwing NullReferenceException
+-   `import` may now raise errors with more detail than "No module named X"
+-   Exception stacktraces on `PythonException.StackTrace` are now properly formatted
+-   Providing an invalid type parameter to a generic type or method produces a helpful Python error
 
 ### Removed
 

diff --git a/src/embed_tests/TestPythonException.cs b/src/embed_tests/TestPythonException.cs
@@ -65,7 +65,21 @@ public void TestPythonExceptionFormat()
             }
             catch (PythonException ex)
             {
-                Assert.That(ex.Format(), Does.Contain("Traceback").And.Contains("(most recent call last):").And.Contains("ValueError: Error!"));
+                // Console.WriteLine($"Format: {ex.Format()}");
+                // Console.WriteLine($"Stacktrace: {ex.StackTrace}");
+                Assert.That(
+                    ex.Format(),
+                    Does.Contain("Traceback")
+                    .And.Contains("(most recent call last):")
+                    .And.Contains("ValueError: Error!")
+                );
+
+                // Check that the stacktrace is properly formatted
+                Assert.That(
+                    ex.StackTrace,
+                    Does.Not.StartWith("[")
+                    .And.Not.Contain("\\n")
+                );
             }
         }
 

diff --git a/src/runtime/pythonexception.cs b/src/runtime/pythonexception.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Linq;
 using System.Runtime.CompilerServices;
 using System.Text;
 
@@ -13,9 +14,9 @@ public class PythonException : System.Exception, IDisposable
         private IntPtr _pyType = IntPtr.Zero;
         private IntPtr _pyValue = IntPtr.Zero;
         private IntPtr _pyTB = IntPtr.Zero;
-        private string _tb = "";
-        private string _message = "";
-        private string _pythonTypeName = "";
+        private readonly string _tb = "";
+        private readonly string _message = "";
+        private readonly string _pythonTypeName = "";
         private bool disposed = false;
         private bool _finalized = false;
 
@@ -44,16 +45,23 @@ public PythonException()
                 }
                 _message = type + " : " + message;
             }
+
             if (_pyTB != IntPtr.Zero)
             {
-                using (PyObject tb_module = PythonEngine.ImportModule("traceback"))
-                {
-                    Runtime.XIncref(_pyTB);
-                    using (var pyTB = new PyObject(_pyTB))
-                    {
-                        _tb = tb_module.InvokeMethod("format_tb", pyTB).ToString();
-                    }
+                using PyObject tb_module = PythonEngine.ImportModule("traceback");
+
+                Runtime.XIncref(_pyTB);
+                using var pyTB = new PyObject(_pyTB);
+
+                using var tbList = tb_module.InvokeMethod("format_tb", pyTB);
+
+                var sb = new StringBuilder();
+                // Reverse Python's traceback list to match the order used in C#
+                // stacktraces
+                foreach (var line in tbList.Reverse()) {
+                    sb.Append(line.ToString());
                 }
+                _tb = sb.ToString();
             }
             PythonEngine.ReleaseLock(gs);
         }
@@ -136,10 +144,7 @@ public override string Message
         /// <remarks>
         /// A string representing the python exception stack trace.
         /// </remarks>
-        public override string StackTrace
-        {
-            get { return _tb + base.StackTrace; }
-        }
+        public override string StackTrace => $"{_tb}===\n{base.StackTrace}";
 
         /// <summary>
         /// Python error type name.