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Managed exception from Python code is always transformed to PythonException #1443

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tibortakacs opened this issue Apr 16, 2021 · 7 comments
Closed

Managed exception from Python code is always transformed to PythonException #1443

tibortakacs opened this issue Apr 16, 2021 · 7 comments

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@tibortakacs
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tibortakacs commented Apr 16, 2021 •
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Environment

  • Pythonnet version: 3.0.0 preview
  • Python version: 3.8 win32
  • Operating System: Windows
  • .NET Runtime: .NET 5

Summary

If there is a callback from .NET to Python, and the Python code raises a .NET type exception, instead of the corresponding real .NET exception was rethrown on the .NET side (after marshalling), always Python.Runtime.PythonException is thrown.

Details

.NET snippet

class Foo
{
    public static void Bar(Action action)
    {
        try
        {
            action.Invoke();
            Console.WriteLine("No exception.");
        }
        catch (NullReferenceException)
        {
            Console.WriteLine("Null reference caught.");
        }
        catch (Exception ex)
        {
             Console.WriteLine("General exception caught: " + ex.GetType().Type); 
        }
    }
}

Python snippet

# .NET imports
from System import NullReferenceException, Action
from MyProgram import Foo

# Preparation
def call():
    raise NullReferenceException()

action = Action(call)

# Action
Foo.Bar(action)

Expected output:
Null reference caught.

Actual output:
General exception caught: Python.Runtime.PythonException
@tibortakacs tibortakacs changed the title Managed exception from Python code transformed to PythonException Managed exception from Python code is always transformed to PythonException Apr 16, 2021
@lostmsu
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lostmsu commented Apr 16, 2021

In 2.x this is by design.
In 3.x the work is already in progress: #1134

@tibortakacs
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@lostmsu Amazing, thank you. I see great progress has been achieved there.

Is there any workaround in the meantime that you can recommend?
Can I ask whether there is an estimation of merging this back into master? (Just asking this because if it will be available in the near future, I do not redesign our code with a workaround.)

@lostmsu
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lostmsu commented Apr 16, 2021

@tibortakacs you can try simply using the branch from the PR.

@tibortakacs
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@lostmsu Amazing, it works properly, not only in the simplified code but also in the real application. Based on this great progress, is it fair to say that there is a chance that it will be merged back into master in the next few weeks? (I am really sorry if my question seems to be "pushy", I am just more comfortable releasing our application based on the master if possible.)

@lostmsu
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lostmsu commented Apr 16, 2021

A chance, yes. But I can not guarantee you that. I'd probably be more certain about the end of May.

@tibortakacs
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@lostmsu Thank you, looking forward to it. If there any way I can support your work (e.g. I am happy to test it with our application regularly), please let me know.

@lostmsu
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lostmsu commented Sep 23, 2021

Corresponding PR has been merged

@lostmsu lostmsu closed this as completed Sep 23, 2021
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@lostmsu @tibortakacs