René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Creating a Python class extending a C# interface with generic return type causes a `System.TypeLoadException: VTable setup of type`","articleBody":"### Environment\r\n\r\n-   Pythonnet version: 3.0.4\r\n-   Python version: 3.10.12\r\n-   Operating System: Ubuntu 22.04 LTS\r\n-   .NET Runtime: Mono 6.12.0.200 (tarball)\r\n\r\n### Details\r\n\r\n-   Describe what you were trying to get done.\r\n\r\nI've stumbled upon an exception when creating a Type in Python from a C# interface that includes a generic return type (example code below)\r\n\r\n-   What commands did you run to trigger this issue? If you can provide a\r\n    [Minimal, Complete, and Verifiable example](http://stackoverflow.com/help/mcve)\r\n    this will help us understand the issue.\r\n\r\n\r\n```c#\r\nnamespace Robin\r\n{\r\n    public interface IRobin\r\n    {\r\n        T? Find\u003cT\u003e() where T : IRobin;\r\n    }\r\n}\r\n```\r\n\r\nConverted to a DLL using: `csc /t:library IRobin.cs`\r\n\r\nThen bug validated with:\r\n\r\n```python\r\nimport sys\r\nimport os\r\nimport pythonnet\r\n\r\nprint(__file__)\r\nsys.path.append(os.path.dirname(os.path.realpath(__file__)))\r\n\r\nimport clr\r\n\r\nclr.AddReference(\"IRobin\")\r\nfrom Robin import IRobin\r\n\r\nprint(pythonnet.get_runtime_info())\r\n\r\nclass A(IRobin):\r\n    __namespace__ = \"mock\"\r\n```\r\n\r\n-   If there was a crash, please include the traceback here.\r\n\r\n```python\r\nTypeError: Failed to create Python type for mock.A\r\n```\r\n\r\nI modified the Pythonnet.dll to console error the C# exception and I get:\r\n\r\n```c#\r\nPython.Runtime.InternalPythonnetException: Failed to create Python type for mock.A ---\u003e System.TypeLoadException: VTable setup of type mock.A failed\r\n  at (wrapper managed-to-native) System.RuntimeType.GetMethodsByName_native(System.RuntimeType,intptr,System.Reflection.BindingFlags,System.RuntimeType/MemberListType)\r\n  at System.RuntimeType.GetMethodsByName (System.String name, System.Reflection.BindingFlags bindingAttr, System.RuntimeType+MemberListType listType, System.RuntimeType reflectedType) [0x0001b] in \u003cd636f104d58046fd9b195699bcb1a744\u003e:0 \r\n  at System.RuntimeType.GetMethodCandidates (System.String name, System.Reflection.BindingFlags bindingAttr, System.Reflection.CallingConventions callConv, System.Type[] types, System.Int32 genericParamCount, System.Boolean allowPrefixLookup) [0x00010] in \u003cd636f104d58046fd9b195699bcb1a744\u003e:0 \r\n  at System.RuntimeType.GetMembers (System.Reflection.BindingFlags bindingAttr) [0x00000] in \u003cd636f104d58046fd9b195699bcb1a744\u003e:0 \r\n  at Python.Runtime.ClassManager.GetClassInfo (System.Type type, Python.Runtime.ClassBase impl) [0x00028] in \u003c2aa3218182dd47ff892dddbce801f07b\u003e:0 \r\n  at Python.Runtime.ClassManager.InitClassBase (System.Type type, Python.Runtime.ClassBase impl, Python.Runtime.ReflectedClrType pyType) [0x00001] in \u003c2aa3218182dd47ff892dddbce801f07b\u003e:0 \r\n  at Python.Runtime.ReflectedClrType.GetOrCreate (System.Type type) [0x00047] in \u003c2aa3218182dd47ff892dddbce801f07b\u003e:0 \r\n   --- End of inner exception stack trace ---\r\n  at Python.Runtime.ReflectedClrType.GetOrCreate (System.Type type) [0x00076] in \u003c2aa3218182dd47ff892dddbce801f07b\u003e:0 \r\n  at Python.Runtime.ReflectedClrType.CreateSubclass (Python.Runtime.ClassBase baseClass, System.Collections.Generic.IList`1[T] interfaces, System.String name, System.String assembly, System.String ns, Python.Runtime.BorrowedReference dict) [0x0001f] in \u003c2aa3218182dd47ff892dddbce801f07b\u003e:0 Traceback (most recent call last):\r\n```\r\n\r\nWith a bit more console out I found the issue is when we try to get the members of the Python class: https://github.com/pythonnet/pythonnet/blob/v3.0.4/src/runtime/ClassManager.cs#L344\r\n","author":{"url":"https://github.com/robin-moss","@type":"Person","name":"robin-moss"},"datePublished":"2024-11-15T15:30:08.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/2511/pythonnet/issues/2511"}