Fix crash when event does not have Add method and improve message for some other internal errors (#2409)

lostmsu · web-flow · commit 9ebfbde35eef · 2024-07-02T08:13:03.000+02:00
* not all events have Add method fixes #2405 * give users some idea of why we might be unable to reflect .NET types to Python for them * mentioned event Add method crash fix in changelog
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -22,6 +22,7 @@ This document follows the conventions laid out in [Keep a CHANGELOG][].
 ### Fixed
 
 -   Fixed RecursionError for reverse operators on C# operable types from python. See #2240
+-   Fixed crash when .NET event has no `AddMethod`
 -   Fixed probing for assemblies in `sys.path` failing when a path in `sys.path` has invalid characters. See #2376
 
 ## [3.0.3](https://github.com/pythonnet/pythonnet/releases/tag/v3.0.3) - 2023-10-11
diff --git a/src/runtime/ClassManager.cs b/src/runtime/ClassManager.cs
@@ -290,11 +290,13 @@ internal static void InitClassBase(Type type, ClassBase impl, ReflectedClrType p
 
         internal static bool ShouldBindMethod(MethodBase mb)
         {
+            if (mb is null) throw new ArgumentNullException(nameof(mb));
             return (mb.IsPublic || mb.IsFamily || mb.IsFamilyOrAssembly);
         }
 
         internal static bool ShouldBindField(FieldInfo fi)
         {
+            if (fi is null) throw new ArgumentNullException(nameof(fi));
             return (fi.IsPublic || fi.IsFamily || fi.IsFamilyOrAssembly);
         }
 
@@ -326,7 +328,7 @@ internal static bool ShouldBindProperty(PropertyInfo pi)
 
         internal static bool ShouldBindEvent(EventInfo ei)
         {
-            return ShouldBindMethod(ei.GetAddMethod(true));
+            return ei.GetAddMethod(true) is { } add && ShouldBindMethod(add);
         }
 
         private static ClassInfo GetClassInfo(Type type, ClassBase impl)
diff --git a/src/runtime/InternalPythonnetException.cs 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
@@ -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;
     }
