[issue32231] -bb option should override -W options

[STINNER Victor]

Change by STINNER Victor :


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stage: needs patch -> resolved
status: open -> closed

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[issue32231] -bb option should override -W options

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:

This looks like a duplicate of issue20361.

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nosy: +serhiy.storchaka
resolution:  -> duplicate
superseder:  -> -W command line options and PYTHONWARNINGS environmental 
variable should not override -b / -bb command line options

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[issue32231] -bb option should override -W options

[Nick Coghlan]

Nick Coghlan  added the comment:

One potential complication here is that embedding applications would inherit 
the requirement to do both:

Py_BytesWarningFlag = 2;

and

PySys_AddWarnOption(L"error::BytesWarning");

to request errors. That's probably OK though, since we're getting into pretty 
esoteric configuration behaviour at that point.

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[issue32231] -bb option should override -W options

[Nick Coghlan]

Nick Coghlan  added the comment:

I'm hesitant to put the *true* default filters in sys.warnoptions, as folks use 
"bool(sys.warnoptions)" as a check for "Were any warning options set via the 
environment or the command line?", and we don't want to invalidate that use 
case.

However, I'm definitely a fan of having the warnings module *only* look at 
sys.warnoptions, and requiring *all* command line options to route their filter 
settings through that channel.

https://bugs.python.org/issue32230 adjusts "-X dev" to work that way, and I'm 
suggesting we do the same here for "-b".

That way, we can fully define the relative ordering of PYTHONWARNINGS, "-X 
dev", "-W", and "-b" inside pymain_add_warnings_options (and only the true 
default filters will be appended by the warnings module itself).

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[issue32231] -bb option should override -W options

[STINNER Victor]

STINNER Victor  added the comment:

IMHO the root issue is that there are different options which set warnings 
filters:

- PYTHONWARNINGS/-W will fill sys.warnoptions
- sys.flags.bytes_warning (-b, -bb) and sys.flags.dev_mode (-X dev, 
PYTHONDEVMODE=1) which change the default filters

vstinner@apu$ ./python -W default -b -c 'import pprint, sys, warnings; 
pprint.pprint(warnings.filters); pprint.pprint(sys.warnoptions)'
[('default', None, , None, 0),
 ('default', None, , None, 0),
 ('default', None, , None, 0)]
['default']

Why default::BytesWarning isn't in sys.warnoptions?

I suggest to experiment to create all filters at once in a single list, rather 
than having sys.warnoptions on one side and init_filters() (Python/_warnings.c) 
on another side.

It was on my TODO list for the PEP 432 :-) Currently, when Python is embedded, 
it's not easy to control filters created by init_filters() which can be an 
issue. I expect a feature like Py_SetPath() to override *all* warnings filters, 
not only "add" filters on top on existing filters, for the specific case of 
embedded Python.

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[issue32231] -bb option should override -W options

[Nick Coghlan]

Nick Coghlan  added the comment:

(From the discussion at https://bugs.python.org/issue32230#msg307721)

Another benefit we'd gain from this approach is that we could easily omit the 
filter entirely in the case where neither -b nor -bb is set: in those 
situations, BytesWarning won't be emitted at all, so we don't really need to 
define a filter for it.

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[issue32231] -bb option should override -W options

[Nick Coghlan]

New submission from Nick Coghlan :

When implementing the "-X dev" mode, Victor was asked to make it behave 
differently from "-Wd", such that "python -bb -X dev" would still raise errors 
for bytes comparisons.

I don't think making "-X dev" and "-Wd" inconsistent with each other is the 
right way to address that request. Instead, I think we should find a way to 
make "-bb" *always* take precedence over any supplied "-W" options.

One way to do that would be to adopt an approach similar to what I've proposed 
for "-X dev" in https://bugs.python.org/issue32230: instead of making the 
warnings module aware of the "-bb" setting, we'd instead adjust the 
initialisation code to inject "error::BytesWarning" into sys.warnoptions 
*after* all of the entries from environment variables and the command line.

--
messages: 307717
nosy: ncoghlan, vstinner
priority: normal
severity: normal
stage: needs patch
status: open
title: -bb option should override -W options
type: enhancement
versions: Python 3.7

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