Adjust stacklevel of implprefix warning

[crazymerlyn]

Fixes #166.

[crazymerlyn]

The build is failing due to a recent change in pytest which adds a wrapper for warnings.warn function for python 2 (thus, changing the stack). Not sure what the best solution is here.
Adding a simple if 'stacklevel' in kwargs: kwargs['stacklevel'] += 1 in the wrapper function could work.

[goodboy]

@crazymerlyn thanks for the PR 👍!
@nicoddemus might know the right tweak to make.

[nicoddemus]

Adding a simple if 'stacklevel' in kwargs: kwargs['stacklevel'] += 1 in the wrapper function could work.

Oh indeed, good catch. What do you think @asottile?

[asottile]

Adding a simple if 'stacklevel' in kwargs: kwargs['stacklevel'] += 1 in the wrapper function could work.

Oh indeed, good catch. What do you think @asottile?

oh! I see what you're saying now -- I was wracking my brain to figure out what was meant here.

if isinstance(kwargs.get('stacklevel'), int):
    kwargs['stacklevel'] += 1

might be safer

probably PR that to pytest and we can get it into 3.9.2?

[crazymerlyn]

if isinstance(kwargs.get('stacklevel'), int):
    kwargs['stacklevel'] += 1

might be safer

probably PR that to pytest and we can get it into 3.9.2?

Yeah, that seems better. But while we are on this, I think stacklevel also needs to be changed if it is not present in kwargs. The default value is 1. So, if somebody uses recwarn in python2.7, the warning will present itself at the wrapper function rather than the line causing the warning.
How about this:

if isinstance(kwargs.get('stacklevel'), int):
    kwargs['stacklevel'] += 1
elif 'stacklevel' not in kwargs:
    kwargs['stacklevel'] = 2

[asottile]

ah in that case even easier:

kwargs.setdefault('stacklevel', 1)
kwargs['stacklevel'] += 1

[crazymerlyn]

So, I tried adding this change to a PR but got a few errors with test_deprecated_call_modes and test_can_capture_previously_captured. Not really sure what's going wrong (python apparently uses a c extension for warnings.warn so pdb wasn't much help).

[asottile]

hmm yeah this is probably the __warningregistry__ bits. link your branch? I'll poke at it since I broke this 😭

[nicoddemus]

I'll poke at it since I broke this

Heh, that's all good and part of the game 😁

[crazymerlyn]

@asottile https://github.com/crazymerlyn/pytest/tree/fix_recwarn_stacklevel.

[asottile]

not pretty, but at least this is throwaway :'( pytest-dev/pytest#4192

[asottile]

sorry about the trouble again, thanks for the report! 🎉

[goodboy]

@nicoddemus good to go here yah?

[asottile]

yah!

[edmorley]

Many thanks!