From dfb46a61f6d838c07d2db1d87f5565cb2c84775e Mon Sep 17 00:00:00 2001
From: Victor Nova <lost@losttech.software>
Date: Mon, 1 Jul 2024 15:02:01 -0700
Subject: [PATCH] give users some idea of why we might be unable to reflect
 .NET types to Python for them

---
 src/runtime/InternalPythonnetException.cs |  9 +++++++
 src/runtime/Types/ReflectedClrType.cs     | 31 ++++++++++++++---------
 2 files changed, 28 insertions(+), 12 deletions(-)
 create mode 100644 src/runtime/InternalPythonnetException.cs

diff --git a/src/runtime/InternalPythonnetException.cs b/src/runtime/InternalPythonnetException.cs
new file mode 100644
index 000000000..d0ea1bece
--- /dev/null
+++ b/src/runtime/InternalPythonnetException.cs
@@ -0,0 +1,9 @@
+using System;
+
+namespace Python.Runtime;
+
+public class InternalPythonnetException : Exception
+{
+    public InternalPythonnetException(string message, Exception innerException)
+        : base(message, innerException) { }
+}
diff --git a/src/runtime/Types/ReflectedClrType.cs b/src/runtime/Types/ReflectedClrType.cs
index 3d0aa7e99..df9b26c29 100644
--- a/src/runtime/Types/ReflectedClrType.cs
+++ b/src/runtime/Types/ReflectedClrType.cs
@@ -30,22 +30,29 @@ public static ReflectedClrType GetOrCreate(Type type)
             return pyType;
         }
 
-        // Ensure, that matching Python type exists first.
-        // It is required for self-referential classes
-        // (e.g. with members, that refer to the same class)
-        pyType = AllocateClass(type);
-        ClassManager.cache.Add(type, pyType);
+        try
+        {
+            // Ensure, that matching Python type exists first.
+            // It is required for self-referential classes
+            // (e.g. with members, that refer to the same class)
+            pyType = AllocateClass(type);
+            ClassManager.cache.Add(type, pyType);
 
-        var impl = ClassManager.CreateClass(type);
+            var impl = ClassManager.CreateClass(type);
 
-        TypeManager.InitializeClassCore(type, pyType, impl);
+            TypeManager.InitializeClassCore(type, pyType, impl);
 
-        ClassManager.InitClassBase(type, impl, pyType);
+            ClassManager.InitClassBase(type, impl, pyType);
 
-        // Now we force initialize the Python type object to reflect the given
-        // managed type, filling the Python type slots with thunks that
-        // point to the managed methods providing the implementation.
-        TypeManager.InitializeClass(pyType, impl, type);
+            // Now we force initialize the Python type object to reflect the given
+            // managed type, filling the Python type slots with thunks that
+            // point to the managed methods providing the implementation.
+            TypeManager.InitializeClass(pyType, impl, type);
+        }
+        catch (Exception e)
+        {
+            throw new InternalPythonnetException($"Failed to create Python type for {type.FullName}", e);
+        }
 
         return pyType;
     }