Support Passing a Proxy object to traceback.TracebackExcetion() for "exc_type"

[ericsnowcurrently]

Feature or enhancement

Currently traceback.TracebackException appears to expect the "exc_type" argument to be None or an exception type object. ¹²

In addition to exception types, I'd like to be able to pass in either a str (the type's __qualname__) or an object that has the attributes that TracebackException need in order to do its job.

For exception types the following attributes are especially important for _PyErr_Display():

• __name__
• __qualname__
• __module__

So we would need those. If non-str were passed in then it would need to have those attrs set properly. If a str were passed in then we'd parse out the info and create a types.SimpleNamespace with that info to use instead.

My motivation is propagating exceptions between interpreters. I want to use TracebackException but have it be strictly a snapshot of an exception, whereas right now it actually still holds a reference to exc_type. It also matters when pickling, where you may not want to pickle a user-defined exception type.

Linked PRs

• gh-111922: Allow Using a Minimal Proxy for TracebackException.exc_type #112324

Footnotes

1. https://github.com/python/cpython/blob/6f09f69b7f85962f66d10637c3325bbb2b2d9853/Lib/traceback.py#L722 ↩

2. https://github.com/python/cpython/blob/6f09f69b7f85962f66d10637c3325bbb2b2d9853/Lib/traceback.py#L763 ↩

[iritkatriel]

I want to suggest an alternative which I think is more in the spirit of what TracebackException is supposed to be (a lightweight snapshot): #112333

[ericsnowcurrently]

I'm closing this in favor of gh-112332 (and gh-112333).