poor exception handling of monkeypatch.setattr on property-decorated attributes

Occasionally, I make the mistake of monkeypatch.setattr the name of a property-decorated attribute rather than the underlying attribute that is referenced by the property. In this situation, pytest fails to monkeypatch-set an attribute that doesn't exist -- makes sense. What doesn't make sense is the exception that is raised.

take, for instance, this basic test module:

import pytest

class MockClass:

    def __init__(self):
        self._name = 'mockymocky'

    @property
    def name(self):
        return self._name

def test_anything(monkeypatch):
    mc = MockClass()
    monkeypatch.setattr(mc, 'name', 'anything')
    assert mc.name == 'anything'

monkeypatch.setattr(mc, 'name', 'anything') raises "INTERNALERROR> IndexError: list index out of range" exception when running a pytest.

Would you please consider creating a more descriptive exception that describes this kind of problem?

Full traceback:

Traceback (most recent call last):
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/main.py", line 90, in wrap_session
    session.exitstatus = doit(config, session) or 0
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/main.py", line 121, in _main
    config.hook.pytest_runtestloop(session=session)
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/vendored_packages/pluggy.py", line 724, in __call__
    return self._hookexec(self, self._nonwrappers + self._wrappers, kwargs)
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/vendored_packages/pluggy.py", line 338, in _hookexec
    return self._inner_hookexec(hook, methods, kwargs)
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/vendored_packages/pluggy.py", line 333, in <lambda>
    _MultiCall(methods, kwargs, hook.spec_opts).execute()
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/vendored_packages/pluggy.py", line 596, in execute
    res = hook_impl.function(*args)
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/main.py", line 146, in pytest_runtestloop
    item.config.hook.pytest_runtest_protocol(item=item, nextitem=nextitem)
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/vendored_packages/pluggy.py", line 724, in __call__
    return self._hookexec(self, self._nonwrappers + self._wrappers, kwargs)
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/vendored_packages/pluggy.py", line 338, in _hookexec
    return self._inner_hookexec(hook, methods, kwargs)
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/vendored_packages/pluggy.py", line 333, in <lambda>
    _MultiCall(methods, kwargs, hook.spec_opts).execute()
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/vendored_packages/pluggy.py", line 595, in execute
    return _wrapped_call(hook_impl.function(*args), self.execute)
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/vendored_packages/pluggy.py", line 253, in _wrapped_call
    return call_outcome.get_result()
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/vendored_packages/pluggy.py", line 278, in get_result
    raise ex[1].with_traceback(ex[2])
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/vendored_packages/pluggy.py", line 264, in __init__
    self.result = func()
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/vendored_packages/pluggy.py", line 596, in execute
    res = hook_impl.function(*args)
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/runner.py", line 65, in pytest_runtest_protocol
    runtestprotocol(item, nextitem=nextitem)
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/runner.py", line 77, in runtestprotocol
    nextitem=nextitem))
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/runner.py", line 121, in call_and_report
    report = hook.pytest_runtest_makereport(item=item, call=call)
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/vendored_packages/pluggy.py", line 724, in __call__
    return self._hookexec(self, self._nonwrappers + self._wrappers, kwargs)
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/vendored_packages/pluggy.py", line 338, in _hookexec
    return self._inner_hookexec(hook, methods, kwargs)
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/vendored_packages/pluggy.py", line 333, in <lambda>
    _MultiCall(methods, kwargs, hook.spec_opts).execute()
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/vendored_packages/pluggy.py", line 595, in execute
    return _wrapped_call(hook_impl.function(*args), self.execute)
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/vendored_packages/pluggy.py", line 249, in _wrapped_call
    wrap_controller.send(call_outcome)
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/skipping.py", line 170, in pytest_runtest_makereport
    rep = outcome.get_result()
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/vendored_packages/pluggy.py", line 278, in get_result
    raise ex[1].with_traceback(ex[2])
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/vendored_packages/pluggy.py", line 264, in __init__
    self.result = func()
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/vendored_packages/pluggy.py", line 596, in execute
    res = hook_impl.function(*args)
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/runner.py", line 227, in pytest_runtest_makereport
    style=item.config.option.tbstyle)
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/python.py", line 715, in _repr_failure_py
    style=style)
  File "/home/florian/.venv/local/lib/python3.4/site-packages/_pytest/main.py", line 410, in _repr_failure_py
    style=style, tbfilter=tbfilter)
  File "/home/florian/.venv/local/lib/python3.4/site-packages/py/_code/code.py", line 412, in getrepr
    return fmt.repr_excinfo(self)
  File "/home/florian/.venv/local/lib/python3.4/site-packages/py/_code/code.py", line 590, in repr_excinfo
    reprtraceback = self.repr_traceback(excinfo)
  File "/home/florian/.venv/local/lib/python3.4/site-packages/py/_code/code.py", line 577, in repr_traceback
    last = traceback[-1]
  File "/home/florian/.venv/local/lib/python3.4/site-packages/py/_code/code.py", line 284, in __getitem__
    val = super(Traceback, self).__getitem__(key)
IndexError: list index out of range

@Dowwie

@Dowwie why close this one

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poor exception handling of monkeypatch.setattr on property-decorated attributes #1270

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poor exception handling of monkeypatch.setattr on property-decorated attributes #1270

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The-Compiler commented on Dec 18, 2015

RonnyPfannschmidt commented on Jan 19, 2016

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