[Python-Dev] PEP 538 warning at startup: please remove it (original) (raw)

Nick Coghlan ncoghlan at gmail.com
Mon Jun 26 00:08:12 EDT 2017

On 12 June 2017 at 22:24, Nick Coghlan <ncoghlan at gmail.com> wrote:

On 12 June 2017 at 18:56, Victor Stinner <victor.stinner at gmail.com> wrote:

Hi,

Nick Coghlan pushed his implementation of his PEP 538: nice! Nice step forward to UTF-8 everywhere ;-) I would prefer to not be annoyed by warning messages about encodings at startup if possible: "Python detected LCCTYPE=C: LCCTYPE coerced to C.UTF-8 (set another locale or PYTHONCOERCECLOCALE=0 to disable this locale coercion behavior)." Note that there's an open issue for this linked from the What's New entry: * https://docs.python.org/dev/whatsnew/3.7.html#pep-538-legacy-c-locale-coercion * https://bugs.python.org/issue30565 I suspect the eventual outcome is going to be dropping that particular warning (since it's been problematic for Fedora's 3.6 backport as well, and the problems are due to the warning itself, not the locale coercion), but I'd prefer to keep the notification at least for a while (potentially even until alpha 1). OTOH, I'm also open to being persuaded otherwise if enough folks are running into problems with it just while working on CPython (I'd still like to turn it back on for alpha 1 even if we turn off in the meantime, though).

Following up here for the sake of folks following this thread, but not all the related issues: with the locale warnings enabled by default, we(/I) couldn't even get CPython's own test suite to pass reliably across the full fleet of stable buildbots.

As a result, https://bugs.python.org/issue30565 was implemented in https://github.com/python/cpython/pull/2260, switching us to an opt-in warning model where you have to set PYTHONCOERCECLOCALE=warn to get the notifications on stderr both when locale coercion triggers and when the interpreter runtime itself is initialized in a locale that would have triggered coercion in the CLI. That then becomes a runtime debugging switch (akin to -X faulthandler or -X tracemalloc) for folks investigating surprising locale-related behaviour in 3.7+, rather than something we do by default.

The original PEP has also been updated with a note indicating that the originally accepted approach was found to be impractical: https://www.python.org/dev/peps/pep-0538/#implementation-notes

Cheers, Nick.

-- Nick Coghlan | ncoghlan at gmail.com | Brisbane, Australia

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