Problem with Popen arguments passed as map

Greetings!

I am having an issue when using the package sorl.thumbnail on a Django project. That package produces thumbnails from images using system installed programs (called engines.)

When sorl.thumbnail makes a Popen call here:

https://github.com/jazzband/sorl-thumbnail/blob/22ccd9781462a820f963f57018ad3dcef85053ed/sorl/thumbnail/engines/convert_engine.py#L57

The arguments that are received in your patched Popen are not being interpreted correctly. This is the suspect of the problem:

https://github.com/getsentry/sentry-python/blob/2c0a2ea96882adf69742bd7e79e588564ff5b85c/sentry_sdk/integrations/stdlib.py#L143

Arguments are handled in such a way that the original popen crashes when trying to access args[0], as the args parameter is interpreted (or actually becomes) an empty list.

In my opinion, the problem arises because in sorl.thumbnail the arguments to Popen are passed to a map function first, so that a map object is what gets passed as arguments. I am not sure what’s the effect of a map object being received in your *a of the patched Popen.

Here’s the relevant part of the traceback I am getting:

File "/mnt/d/Proyectos/ginseng/.venv/lib/python3.6/site-packages/sorl/thumbnail/base.py", line 131, in get_thumbnail
    thumbnail)
  File "/mnt/d/Proyectos/ginseng/.venv/lib/python3.6/site-packages/sorl/thumbnail/base.py", line 164, in _create_thumbnail
    default.engine.write(image, options, thumbnail)
  File "/mnt/d/Proyectos/ginseng/.venv/lib/python3.6/site-packages/sorl/thumbnail/engines/convert_engine.py", line 57, in write
    p = subprocess.Popen(args, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
  File "/mnt/d/Proyectos/ginseng/.venv/lib/python3.6/site-packages/sentry_sdk/integrations/stdlib.py", line 165, in sentry_patched_popen_init
    return old_popen_init(self, *a, **kw)
  File "/usr/lib/python3.6/subprocess.py", line 729, in __init__
    restore_signals, start_new_session)
  File "/usr/lib/python3.6/subprocess.py", line 1248, in _execute_child
    executable = args[0]
IndexError: list index out of range

If I remove the Sentry integration altogether from the Django project, sorl.thumbnail is able to effectively call Popen with the “mapped” arguments, and everything works.

Thanks in advance!

[untitaker]

@WilliamMayor to be clear we will fix the SDK to not change the real-world behavior of subprocess, so if your end goal here is to get a newer version of the SDK working again, just wait for a release. I am just saying that those upstream libraries are also broken in the sense that they use the stdlib in an undocumented way and are unlikely to work on PyPy, and I would apprechiate it if somebody went to those projects and made their maintainers aware. There seem to be multiple of them.

[WilliamMayor]

I experienced this with Django’s collectstatic command running pysassc. I had to downgrade to version 0.9.5 (the last working version I’d used) to get my Heroku deploys to start working again.