When missing the `method` argument of `teardown_method`, getting `INTERNALERROR`

[guyzmo]

Context: I'm using pytest 2.9.2, on Python 3.5, with a bunch of plugins (see outputs).

I have setup a tests module in my project with a test class similar to:

tests/test_project.py:

class TestProject:
    def setup_method(self, method): pass
    def teardown_method(self): pass # oops I forgot the method arg!

    def test_project(self):
        assert True

I ran it, and obtained the following traceback:

Test session starts (platform: linux, Python 3.5.1, pytest 2.9.2, pytest-sugar 0.7.1)
cachedir: .cache
rootdir: …, inifile:
plugins: cov-2.2.1, xdist-1.14, sugar-0.7.1, catchlog-1.2.2, datadir-ng-1.1.0

INTERNALERROR> Traceback (most recent call last):
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/main.py", line 94, in wrap_session
INTERNALERROR>     session.exitstatus = doit(config, session) or 0
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/main.py", line 125, in _main
INTERNALERROR>     config.hook.pytest_runtestloop(session=session)
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/vendored_packages/pluggy.py", line 724, in __call__
INTERNALERROR>     return self._hookexec(self, self._nonwrappers + self._wrappers, kwargs)
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/vendored_packages/pluggy.py", line 338, in _hookexec
INTERNALERROR>     return self._inner_hookexec(hook, methods, kwargs)
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/vendored_packages/pluggy.py", line 333, in <lambda>
INTERNALERROR>     _MultiCall(methods, kwargs, hook.spec_opts).execute()
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/vendored_packages/pluggy.py", line 596, in execute
INTERNALERROR>     res = hook_impl.function(*args)
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/main.py", line 150, in pytest_runtestloop
INTERNALERROR>     item.config.hook.pytest_runtest_protocol(item=item, nextitem=nextitem)
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/vendored_packages/pluggy.py", line 724, in __call__
INTERNALERROR>     return self._hookexec(self, self._nonwrappers + self._wrappers, kwargs)
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/vendored_packages/pluggy.py", line 338, in _hookexec
INTERNALERROR>     return self._inner_hookexec(hook, methods, kwargs)
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/vendored_packages/pluggy.py", line 333, in <lambda>
INTERNALERROR>     _MultiCall(methods, kwargs, hook.spec_opts).execute()
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/vendored_packages/pluggy.py", line 595, in execute
INTERNALERROR>     return _wrapped_call(hook_impl.function(*args), self.execute)
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/vendored_packages/pluggy.py", line 253, in _wrapped_call
INTERNALERROR>     return call_outcome.get_result()
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/vendored_packages/pluggy.py", line 278, in get_result
INTERNALERROR>     raise ex[1].with_traceback(ex[2])
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/vendored_packages/pluggy.py", line 264, in __init__
INTERNALERROR>     self.result = func()
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/vendored_packages/pluggy.py", line 596, in execute
INTERNALERROR>     res = hook_impl.function(*args)
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/runner.py", line 66, in pytest_runtest_protocol
INTERNALERROR>     runtestprotocol(item, nextitem=nextitem)
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/runner.py", line 78, in runtestprotocol
INTERNALERROR>     nextitem=nextitem))
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/runner.py", line 122, in call_and_report
INTERNALERROR>     report = hook.pytest_runtest_makereport(item=item, call=call)
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/vendored_packages/pluggy.py", line 724, in __call__
INTERNALERROR>     return self._hookexec(self, self._nonwrappers + self._wrappers, kwargs)
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/vendored_packages/pluggy.py", line 338, in _hookexec
INTERNALERROR>     return self._inner_hookexec(hook, methods, kwargs)
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/vendored_packages/pluggy.py", line 333, in <lambda>
INTERNALERROR>     _MultiCall(methods, kwargs, hook.spec_opts).execute()
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/vendored_packages/pluggy.py", line 595, in execute
INTERNALERROR>     return _wrapped_call(hook_impl.function(*args), self.execute)
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/vendored_packages/pluggy.py", line 249, in _wrapped_call
INTERNALERROR>     wrap_controller.send(call_outcome)
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/skipping.py", line 226, in pytest_runtest_makereport
INTERNALERROR>     rep = outcome.get_result()
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/vendored_packages/pluggy.py", line 278, in get_result
INTERNALERROR>     raise ex[1].with_traceback(ex[2])
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/vendored_packages/pluggy.py", line 264, in __init__
INTERNALERROR>     self.result = func()
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/vendored_packages/pluggy.py", line 596, in execute
INTERNALERROR>     res = hook_impl.function(*args)
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/runner.py", line 232, in pytest_runtest_makereport
INTERNALERROR>     style=item.config.option.tbstyle)
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/python.py", line 745, in _repr_failure_py
INTERNALERROR>     style=style)
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/main.py", line 408, in _repr_failure_py
INTERNALERROR>     style=style, tbfilter=tbfilter)
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/_code/code.py", line 418, in getrepr
INTERNALERROR>     return fmt.repr_excinfo(self)
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/_code/code.py", line 599, in repr_excinfo
INTERNALERROR>     reprcrash = excinfo._getreprcrash()
INTERNALERROR>   File …/pytest-2.9.2-py3.5.egg/_pytest/_code/code.py", line 395, in _getreprcrash
INTERNALERROR>     entry = self.traceback.getcrashentry()
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/_code/code.py", line 314, in getcrashentry
INTERNALERROR>     return self[-1]
INTERNALERROR>   File "…/pytest-2.9.2-py3.5.egg/_pytest/_code/code.py", line 289, in __getitem__
INTERNALERROR>     val = super(Traceback, self).__getitem__(key)
INTERNALERROR> IndexError: list index out of range


Results (0.18s):
       1 passed

I ran the test again with --fulltraceback and had the traceback telling me that I'm wrong, with no issue (cf that gist).

After some discussion on #pylib with @RonnyPfannschmidt, we figured out it's definitely the traceback pruning that's at fault: the exception is thrown within pytest, so when pruning all pytest stuff, there's nothing left.

So as a solution we could do the following to avoid pruning if the last stack entry is from a file in the pytest lib:

at line 387 of _pytest/main.py:

    if self.config.option.fulltrace:
        style="long"
    else:
        if not 'pytest' in excinfo.tb.tb_frame.f_code.co_filename:
            self._prunetraceback(excinfo)
        tbfilter = False  # prunetraceback already does it
        if style == "auto":
            style = "long"

which will return the full stacktrace, as we're avoiding pruning it altogether. It's ok, but I'm not found of the test itself… it's a bit too Q&D.

or we could do the following version that prunes everything, showing only the last item of the stack, where there's useful information to debug:

at line 387 of _pytest/main.py:

    if self.config.option.fulltrace:
        style="long"
    else:
        from ._code.code import Traceback
        tb = Traceback([excinfo.traceback[-1]])
        self._prunetraceback(excinfo)
        if len(excinfo.traceback) == 0:
            excinfo.traceback = tb
        tbfilter = False  # prunetraceback already does it
        if style == "auto":
            style = "long"

which gives:

―――――――――――――――――――――――――――――――――――――――――――――――― ERROR at teardown of TestProject.test_project ―――――――――――――――――――――――――――――――――――――――――――――――――

>   self.addfinalizer(lambda: fin(self.obj))
E   TypeError: teardown_method() takes 1 positional argument but 2 were given

var/eggs/pytest-2.9.2-py3.5.egg/_pytest/python.py:716: TypeError
 tests/test_project.py   

I'd be happy to submit a PR for solving this… But I guess it needs some discussion on whether either of my suggestions are good to solve the issue or not.

[RonnyPfannschmidt]

i consider keeping the last item a good idea for a starting point

a full pr would also need a test exposing the issue

i would propose at a later point to switch pruning with collapsing, so there would be "collapsed pytest internals" entry
but hats for a new issue

[nicoddemus]

Fixed in current master.