[Python-Dev] PEP 565: Show DeprecationWarning in __main__

[Guido van Rossum]

OK, in that case I'll just pronounce approval right here. Considered
disagreement is acceptable.

Nick, congrats with PEP 565! Please update the PEP to mark it as approved
with a link to this message as the resolution, and let's get the
implementation into 3.7a4!

On Tue, Dec 12, 2017 at 2:58 PM, Victor Stinner <victor.stinner at gmail.com>
wrote:

> Hi,
>
> 2017-12-12 21:21 GMT+01:00 Guido van Rossum <guido at python.org>:
> > I'm still hoping to accept this PEP, but I don't have time to wrap my
> head
> > around -Xdev ("devmode"?) which appears to be Victor's latest pet
> project.
> > Should PEP 565 be changed to copy with devmode's behavior, or the other
> way
> > around, or should they just ignore each other? It is not clear of me what
> > the status of the mention in PEP 565 of -Xdev is -- normative or
> > informational? I really don't want to have to learn how devmode works in
> > order to be able to accept PEP 565 (or send it back for revision), so I
> am
> > asking you two to let me know.
>
> The warnings filters had a few corner cases. We discussed with Nick to
> fix them to make them simpler. We agreed on these priorities for
> command line options and environment variables:
>
> -b and -bb > -W > PYTHONWARNINGS > -X dev > default filters
>
> In release mode, the default filters became:
>
>     ignore::DeprecationWarning
>     ignore::PendingDeprecationWarning
>     ignore::ImportWarning
>     ignore::ResourceWarning
>
> ignore::BytesWarning is gone. We now rely on the fact the BytesWarning
> should not be emited without -b nor -bb in practice.
>
> It has been implemented in https://bugs.python.org/issue32230 ! (I
> just merged Nick's PR.)
>
>
> Now -X dev behaves again as my initial propopal: for warnings, "-X
> dev" simply behaves  as "-W default". (Previously, I had to hack the
> code to respect -b and -bb options, but I don't think that it's worth
> it to explain that here, it's doesn't matter anymore ;-))
>
> The PEP 565 is still different: it doesn't behaves as "-W default",
> but "-W default::DeprecationWarning:__main__". Only DeprecationWarning
> warnings are shown, whereas -X dev shows DeprecationWarning, but also
> PendingDeprecationWarning, ResourceWarning and ImportWarning.
> Moreover, -X dev shows warnings in all modules, not only __main__.
>
> You may see -X dev as a builtin linter, whereas PEP 565 seems to be
> very specific to one specific issue: display deprecation warnings, but
> only in the __main__ module.
>
> Does it help you to understand the difference?
>
>
> Note: I still dislike the PEP 565, but well, that's just my opinion ;-)
>
> Victor
>



-- 
--Guido van Rossum (python.org/~guido)
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