Pytest Fails to Run When Passing Long Command Line Arguments

[iandonnelly]

I am seeing an issue when passing a very long command-line argument to pytest. It fails to run with the following error:

INTERNALERROR>   File "/venv/lib/python3.11/site-packages/_pytest/main.py", line 333, in pytest_collection
INTERNALERROR>     session.perform_collect()
INTERNALERROR>   File "/venv/lib/python3.11/site-packages/_pytest/main.py", line 638, in perform_collect
INTERNALERROR>     fspath, parts = resolve_collection_argument(
INTERNALERROR>                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
INTERNALERROR>   File "/venv/lib/python3.11/site-packages/_pytest/main.py", line 889, in resolve_collection_argument
INTERNALERROR>   File "/venv/lib/python3.11/site-packages/_pytest/main.py", line 889, in resolve_collection_argument
INTERNALERROR>     if not fspath.exists():
INTERNALERROR>            ^^^^^^^^^^^^^^^
INTERNALERROR>   File "/usr/local/lib/python3.11/pathlib.py", line 1235, in exists
INTERNALERROR>     self.stat()
INTERNALERROR>   File "/usr/local/lib/python3.11/pathlib.py", line 1013, in stat
INTERNALERROR>     return os.stat(self, follow_symlinks=follow_symlinks)
INTERNALERROR>            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
INTERNALERROR> OSError: [Errno 36] File name too long: '/pwd/tests/very,long,comma-seperated,value,for,long_list'

Pytest version:
Tested with 7.3.2 and 7.4.1

pip list output:

--------------------- ---------
allure-pytest         2.13.2
allure-python-commons 2.13.2
ansi2html             1.8.0
attrs                 23.1.0
boto3                 1.28.40
botocore              1.31.40
certifi               2023.7.22
chardet               5.2.0
charset-normalizer    3.2.0
click                 8.1.3
contourpy             1.0.7
cycler                0.11.0
datadog               0.45.0
execnet               1.9.0
filelock              3.12.0
fonttools             4.39.4
gitdb                 4.0.10
GitPython             3.1.31
idna                  3.4
iniconfig             2.0.0
Jinja2                3.1.2
jmespath              1.0.1
kiwisolver            1.4.4
markdown-it-py        2.2.0
MarkupSafe            2.1.3
matplotlib            3.7.1
mdurl                 0.1.2
numpy                 1.24.3
packaging             23.1
pandas                1.5.3
Pillow                9.5.0
pip                   22.3.1
pluggy                1.0.0
py                    1.11.0
Pygments              2.15.1
pyparsing             3.0.9
pytest                7.4.1
pytest-html           4.0.0
pytest-metadata       2.0.4
pytest-xdist          3.3.1
python-dateutil       2.8.2
pytz                  2022.7.1
requests              2.31.0
rich                  13.3.5
s3transfer            0.6.2
setuptools            65.5.0
six                   1.16.0
smmap                 5.0.0
urllib3               1.26.16

Example usage:

conftest.py:

import pytest

def pytest_addoption(parser):
    parser.addoption("--long-list", dest="long_list", action="store", default="all", help="List of things")

@pytest.fixture(scope="module")
def specified_feeds(request):
    list_string = request.config.getoption("--long-list")
    return list_string.split(',')

Invocation:
pytest /test_my_thing.py --long-list a,b,c,d,e,f

Note: the actual length of the string passed to --long-list is 396 characters

This seems to be similar to #10169

[iandonnelly]

@nicoddemus Tagging you since this is similar to a bug you closed.

[nicoddemus]

@iandonnelly

Note: the actual length of the string passed to --long-list is 396 characters

So the path that appears in the message ('/pwd/tests/very,long,comma-seperated,value,for,long_list') is also very long, correct?

Seems indeed like we need to also surround that exists call with a try/except then.

[iandonnelly]

Exactly, that's my thought as well.

[iandonnelly]

@nicoddemus Now I'm just getting an error that the file or directory isn't found. This command line argument is just a a string that represents a CSV list --arg=a,b,c,word,whatever,pretty_long123,list

The error message is ERROR: file or directory not found: a,b,c,word,whatever,pretty_long123,list

[nicoddemus]

Now I'm just getting an error that the file or directory isn't found.

What changed? Did you try the recently released 7.4.2 version?

[iandonnelly]

@nicoddemus I grabbed from your dev branch, just tried 7.4.2 though and it's the same error I described above. What's the code path look like for parsing command-line arguments? It's correct that that argument isn't a path but why doesn't it just forward the argument as a string?

[nicoddemus]

@iandonnelly can you post the full traceback?

[iandonnelly]

There's no traceback for this, I think the argument just isn't being successfully parsed by pytest. I'll try stepping through the code Monday and see if I can figure out why.

[nicoddemus]

Thanks!

[iandonnelly]

@nicoddemus Sorry for the delay, I figured out what was going on. Our --long-list value had a space in it so pytest was reading it as two arguments (correctly) and there is no file present for that second argument. I think everything is working as expected now and I think handling the OSError is a real improvement anyway so I think we're all ok now.

[nicoddemus]

Nice, thanks for the follow up!