Confusing error message around tmpdir fixture

[asottile]

Simplest reproduction:

import pytest

@pytest.yield_fixture
def tmpdir_factory(tmpdir):
    yield

def test_1(tmpdir):
    pass

$ py.test test.py
============================= test session starts ==============================
platform linux2 -- Python 2.7.6, pytest-2.8.1, py-1.4.30, pluggy-0.3.1
rootdir: /tmp, inifile: 
collected 1 items 

test.py E

==================================== ERRORS ====================================
___________________________ ERROR at setup of test_1 ___________________________
file /tmp/test.py, line 7
  def test_1(tmpdir):
file /tmp/venv/local/lib/python2.7/site-packages/_pytest/tmpdir.py, line 109
  @pytest.fixture
  def tmpdir(request, tmpdir_factory):
file /tmp/test.py, line 3
  @pytest.yield_fixture
  def tmpdir_factory(tmpdir):
        fixture 'tmpdir' not found
        available fixtures: tmpdir_factory, pytestconfig, cache, recwarn, monkeypatch, record_xml_property, capfd, capsys, tmpdir
        use 'py.test --fixtures [testpath]' for help on them.

/tmp/test.py:3
=========================== 1 error in 0.01 seconds ============================

pytest version: 2.8.1

fwiw this breaks my build here: https://travis-ci.org/pre-commit/pre-commit/jobs/83034637

[nicoddemus]

Thanks the report!

The problem is that a new tmpdir_factory was introduced in 2.8 as a builtin fixture, and your fixture is overriding it here because it has the same name. Your fixture uses tmpdir, and the problem is that the builtin tmpdir fixture now requires tmpdir_factory (the builtin), but your fixture overwrote the builtin with your own (which requires tmpdir) hence there's a recursion.

The workaround is to rename your tmpdir_factory fixture to something else, I'm afraid (looking at your code perhaps you can replace your tmpdir_factory implementation with pytest's, they have the same purpose albeit slightly different interfaces).

Not sure how simple it is to fix this in pytest to at least produce a better message, though.

[nicoddemus]

I see you renamed your fixture to tmpdir_factory in pre-commit/pre-commit#270, so I'm closing this for now. 😄