We ran into an issue recently where our pyo3-based library was causing user code to hang, and it took me a full day and a half to track it down. Once we were able to identify the problem (it was hidden behind a few layers of abstraction - unhandled error in a background thread and then some, see BoundaryML/baml#1214), we realized that the root cause of the issue was that in our pyo3 code, we had a PyModule::from_code(..., file_name = "", ...) call.

It turns out that when a user calls inspect.stack() in a Python context, where one of the stack frames references a variable created in this way, inspect.stack() will actually throw because empty filenames (understandably) are errors.

I wonder if PyModule::from_code should just always return PyErr in this scenario.

Pros:

• safer out-of-the-box behavior (user code is more likely to be compatible with inspect)

Cons:

• would a user ever want to deliberately set the filename to ""?
• is this too much of a backwards-breaking change? since this would cause runtime errors, not build errors on pyo3 upgrade