[pytest-dev] [3.1 feature] "assert not raise exception" helper: opinions about the name

[Ronny Pfannschmidt]

Hi all,


my own stance is still to give it a different name,

while experimenting i learned of the fun fact that None is a "valid
exception type"
for except clauses on at least python 2.7
however on python3 it is invalid and a type error,

since the usage patterns of python don't hold such a case,
i'd like to use a distinct building block for expressing it in order to
match the semantics of the language closer

- Ronny

On 04.04.2017 19:19, holger krekel wrote:
> On Tue, Apr 04, 2017 at 15:48 +0000, Bruno Oliveira wrote:
>> On Fri, Mar 31, 2017 at 8:24 AM Bruno Oliveira <nicoddemus at gmail.com> wrote:
>>
>>> Hi all,
>>>
>>> On Fri, Mar 31, 2017 at 7:13 AM Vasily Kuznetsov <kvas.it at gmail.com>
>>> wrote:
>>>
>>> Hi Holger and Ronny,
>>>
>>> I see merit in both of your points. All those "is not None" checks in
>>> between other logic and the proposed "raises unless the argument is None"
>>> semantics of pytest.raises do increase complexity (I'm not qualified to
>>> predict whether or not this increase is significant in terms of further
>>> maintenance though) but at the same time "pytest.raises(None)" API is
>>> convenient in some cases. What if we do something like this:
>>>
>>> ...
>>>
>>> The "is not None" checks are gone from the main logic and both APIs are
>>> available. Or if we would rather not have more than one way to do it, we
>>> can drop "does_not_raise" but otherwise still keep it a separate context.
>>>
>>> Seems like if we can agree on the API, a not-complexity-increasing option
>>> of implementation is possible.
>>>
>>>
>>> Now for the specific case of pytest.raises(None), I believe we can strike
>>> a good balance between a nice user interface and minimal internal impact
>>> like Vasily proposes, unless Ronny or others feel that pytest.raises(None)
>>> is not a good interface for this functionality.
>>>
>> Guys, anything else to add here? I would like to move the implementation
>> forward, either in its current form or changing it to pytest.raises(None).
> i was and am fine with your suggestion!
>
> IMO compared to markers or fixtures ... "pytest.raises" is relatively 
> self-contained side-effect-free code so i don't think it's neccessary
> to get scared about maintanability too much in this case.
>
> cheers, holger
>
>> Ronny, after the discussion here are you still against using
>> ptyest.raises(None), given that we can implement it easily by Vasily's
>> suggested implementation?
>>
>> Cheers,
>> Bruno.