On Fri, Feb 18, 2022 at 7:39 PM Chris Smith <smi...@gmail.com> wrote:
> A concern I have about the policy is that "positional argument names are
> not Public API". I hope this is not correct, because if a function `f(a,
> b)` is changed to `f(b, a)` this would start failing without warning.
The names are different from the order. The name of a positional argument
doesn't matter but the order obviously does.
I'm not even sure that `f(a, b, c=1, d=2)` should be allowed to be changed
> to swap the order of `c` and `d` since the API allows all 4 to be given and
> does not require the defaults to be given. So if `f(1, 2, 3, 4)` started
> returning (silently) the result for `f(1, 2, 4, 3)`, that would be a
> problem.
It depends on the specific keyword argument. In some cases it's not really
something you should ever use without using the keyword name.
It would be good to be more explicit about this by using keyword-only
arguments. If you write
def f(a, b, *, c=1, d=2):
...
Then f(1, 2, 3, 4) is not allowed. You have to write f(1, 2, a=3, b=4). You
can also do a similar thing with / to make things positional only starting
in Python 3.8. Keyword only OTOH has been available ever since we dropped
Python 2.
I think we should use keyword only arguments a lot more, because it makes
the signature future proof against adding more keyword arguments. Making
more things positional only could be good too, although I rarely see people
unnecessarily calling a positional argument as a keyword argument.
I started to do this in https://github.com/sympy/sympy/pull/21803 but some
felt that changing existing signatures was itself a compatibility break (I
disagree, but even if we decide this, it should be possible to make the
change with a custom decorator that just deprecates the old way). Either
way it's a huge undertaking to fix all the signatures in SymPy, but worth
it IMO.
Aaron Meurer
>
> /c
> On Wednesday, January 26, 2022 at 3:38:55 PM UTC-6 Aaron Meurer wrote:
>
>> We are currently in the process of revamping our deprecations policy
>> at https://github.com/sympy/sympy/pull/22900, and we would like any
>> feedback from the community, both users and developers. Our current
>> policy that this would replace is on the wiki
>> https://github.com/sympy/sympy/wiki/Deprecating-policy.
>>
>> In particular, the new policy would have
>>
>> 1. An official period of at least 1 year for all deprecations to last.
>> Previously there was no official period for deprecations, and
>> deprecated functionality was removed more or less whenever we felt
>> like it.
>>
>> 2. Deprecations will still raise a SymPyDeprecationWarning, but the
>> proposed policy is to make the warnings contain much more verbose and
>> helpful messages. In addition, all warnings will be documented in the
>> respective docstrings, listed in a separate "all active deprecations"
>> document in the docs, and listed in the release notes for each release
>> (currently only the last of these is done).
>>
>> 3. The current silly "deprecation removal issue" thing that we (tried)
>> to do will be removed. All documentation for deprecations will be in
>> the documentation.
>>
>> 4. I have added some text to the document going over when backwards
>> compatibility breaks should be made (tl;dr: sparingly), and what does
>> and doesn't require deprecation to change. The document also has
>> developer instructions on how to add a deprecation to the code.
>>
>> One question we have for users is if you are happy with our current
>> SymPyDeprecationWarnings, which are relatively loud by default (they
>> use a warnings filter that always turns them on). Would you prefer
>> more silent warnings, like warnings that are documented but aren't
>> accompanied by a warning printed to the screen?
>>
>> Aaron Meurer
>>
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