doctest causes a working out of context RuntimeError with request

[alexprengere]

Migrating from Flask 2.1 to 2.2 failed a few unit tests of mine. It looks like we can no longer import flask.request top level in a test file (reproduced across Python 3.7, 3.8, 3.9, 3.10):

from flask import Flask
from flask import request

def test_something():
    assert True

This gives a RuntimeError:

E   RuntimeError: Working outside of request context.
E
E   This typically means that you attempted to use functionality that needed
E   an active HTTP request. Consult the documentation on testing for
E   information about how to avoid this problem.

On my side the fix was simple: importing flask.request outside of the global scope, just when I actually need it (my actual tests create small Flask apps to test a client).

Edit: forgot to mention that this only occurs when pytest is run with --doctest-modules

[davidism]

This used to happen in pallets/flask#1680, but was fixed in Werkzeug #924 a long time ago. Seems it has started happening again.

[davidism]

Running python -m doctest example.py, with just from flask import request in the file, causes the error.

What's happening is that Werkzeug only sets __wrapped__ if the Local wraps a function, but does not set the attribute otherwise. Flask 2.2 started wrapping ContextVar directly instead of a function. Doctest uses inspect.unwrap to access that attribute, which fails with a proxy error instead of an attribute error. This bug was always present with doctest and previous versions, but it was hidden because of the way Flask previously used Local.

Unfortunately, just the presence of __wrapped__ indicates to inspect.unwrap that something is a wrapper. So we can't set it to None, as that would make it present but incorrect.

I really think this is a bug in Python's inspect, it should ignore errors when accessing the attribute, but it's unlikely to get fixed there. The only think we can really do in Werkzeug is to either set the attribute to something incorrect, or see if there's a way to simulate an AttributeError on access.

[davidism]

This was reported in doctest years ago: python/cpython#70186. I think this is an issue with doctest, Sphinx uses inspect.unwrap as well but catches exceptions so that it doesn't fail.

For now, I'll set __wrapped__ to whatever LocalProxy is wrapping, not only if it's wrapping a function.