I think it's been conclusively shown that we should not change the default. Instead I recommend updating the docs with an example showing when stacklevel=2 is appropriate.
On Mon, Sep 21, 2015 at 2:05 AM, Nick Coghlan <ncogh...@gmail.com> wrote: > On 21 September 2015 at 17:21, Nathaniel Smith <n...@pobox.com> wrote: > > On Sep 21, 2015 12:15 AM, "Victor Stinner" <victor.stin...@gmail.com> > wrote: > >> > >> Would it be too verbose to display two frames or more by default? > >> Maybe depending on the action (ex: only if the warning is emitted only > >> once). > > > > It's not just about how it gets displayed -- the frame that it gets > > "attributed" to is also used when comparing against the warnings filters > to > > determine what action to take. What if stacklevel=1 makes it match a > filter > > with action "ignore", and stacklevel=2 makes it match a filter with > action > > "raise"? > > > > (This is a common example I've encountered in the context of wanting to > set > > up CI tests so that if *my* code uses deprecated functionality then I > want > > to fail the test so I notice, but if some library I'm using uses > deprecated > > functionality internally then that's not my problem. This breaks down > when > > the library makes the common error of issuing DeprecationWarnings with > > stacklevel=1, because that makes python think that they are deprecating > > themselves, not warning that I did something deprecated.) > > As Victor notes, though, that's not the right default for *scripts* > that are issuing deprecation warnings to end users - there, they > really are deprecating themselves. It's also not the right default for > pretty much any warning other than DeprecationWarning - for those, > you're generally wanting to say "we hit this problematic code path", > not report anything about your caller. > > Passing "stacklevel=2" for API deprecations is by no means obvious > though, so perhaps it makes sense to add a > "warnings.warn_deprecated(message)" function that's implemented as: > > def warn_deprecated(message, stacklevel=1): > return warnings.warn(message, DeprecationWarning, > stacklevel=(2+stacklevel)). > > Cheers, > Nick. > > -- > Nick Coghlan | ncogh...@gmail.com | Brisbane, Australia > _______________________________________________ > Python-Dev mailing list > Python-Dev@python.org > https://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: > https://mail.python.org/mailman/options/python-dev/guido%40python.org > -- --Guido van Rossum (python.org/~guido)
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