[Twisted-Python] Twisted v21.2.0 breaks Crossbar.io

[Jean-Paul Calderone]

On Tue, Mar 2, 2021 at 3:09 PM Tobias Oberstein <tobias.oberstein at gmail.com>
wrote:

> Hi all,
>
> rgd Twisted v21.2.0, thanks a lot to all involved in this release! the
> release, mypy, more py3, .. +1! really appreciated.
>
> now, fwiw, just wanted to let you know (sorry, too late) about a
> regression with
>
> https://github.com/crossbario/crossbar
>
> that actually originates from
>
> https://github.com/crossbario/autobahn-python/issues/1470
>
> =>
>
> with Twisted v20.3.0 calling
> twisted.internet.protocol.ProcessProtocol.getPeer raises an AttributeError
>
> with Twisted v21.2.0 calling the same method raises an
> NotImplementedError
>
> =>
>
> this fix broke our workaround for the bug now fixed;)
>
> https://github.com/crossbario/autobahn-python/pull/1469/files
>
> and released in:
>
> https://pypi.org/project/autobahn/21.3.1/
> https://pypi.org/project/crossbar/21.3.1/
>
> Cheers,
> /Tobias
>
>
It seems like this change does not actually violate Twisted's compatibility
policy.  This is not to say introducing such regressions is desirable, but
when constructing such work-arounds it might be worth paying
closer-than-average attention to what the policy actually is.

The policy is currently documented at
https://twistedmatrix.com/documents/current/core/development/policy/compatibility-policy.html#new-attributes
(and that anchor takes you to the section that I think allows the change).

Policy aside, this change doesn't seem like much of an improvement to me.
If I were to guess, I would guess the change was made to satisfy some check
Mypy is now being asked to make about Twisted.  If that's the case, it
seems unfortunate that real-world software is suffering so that a synthetic
goal can be achieved.  I do recognize there is a perception that practical
value can come from attending to the errors Mypy reports.  It would
probably benefit everyone if more care were taken to consider the
real-world consequences of changes that are made to satisfy the
non-real-world goalposts set by tools like Mypy.

Jean-Paul



> _______________________________________________
> Twisted-Python mailing list
> Twisted-Python at twistedmatrix.com
> https://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-python
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: </pipermail/twisted-python/attachments/20210302/9243e6b6/attachment.htm>