On Mon, 21 Sep 2015 at 10:15 Serhiy Storchaka <storch...@gmail.com> wrote:
> On 21.09.15 12:05, Nick Coghlan wrote: > > 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. > > If a warning is emitted in library function, user can't do anything with > function's code and should change his code that calls the function. In > this case the warning should point to the line where the function is used. > > If a warning is emitted in user's code, he is able to add explicit > stacklevel=1 if needed. > > stacklevel=2 is correct argument for module level warnings, but as > Nathaniel noted not all packages use it. When your run correctly written > module as script you get the same "sys:1:". And this issue can be solved > in general case. > > not allecause the user wants to get a warning at the place where the > module is imported. > > > 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)). > > This will not fix tons of modules that are not aware of correct stacklevel. > The long-term solution to this is to add a warnings.deprecate_module() function which does the right thing and simply not expose the stacklevel argument to users. We can then consider warnings.warn() more of a power user function and make the stacklevel a keyword-only argument with no default value (although I can already hear Raymond saying "but the Python 2 users" for that part of the idea =).
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