locale.nl_langinfo(locale.ALT_DIGITS) does not work

[serhiy-storchaka]

ALT_DIGITS is a glibc specific item. It is supported by Python (there is an explicit list of supported items), but the result is not correct.

From The GNU C Library Reference Manual:

ALT_DIGITS

The return value is a representation of up to 100 values used to represent the values 0 to 99. As for ERA this value is not intended to be used directly, but instead indirectly through the strftime function. When the modifier O is used in a format which would otherwise use numerals to represent hours, minutes, seconds, weekdays, months, or weeks, the appropriate value for the locale is used instead.

This value is only defined in few locales: az_IR, fa_IR, ja_JP, lzh_TW, my_MM, or_IN, shn_MM.

But Python returns only one digit.

>>> import locale
>>> locale.setlocale(locale.LC_TIME, 'ja_JP')
'ja_JP'
>>> locale.setlocale(locale.LC_CTYPE, 'ja_JP')
'ja_JP'
>>> locale.nl_langinfo(locale.ALT_DIGITS)
'〇'

This is because nl_langinfo(ALT_DIGITS) in C returns a string with embedded null characters.

How should we fix it?

• return a single string with 99 embedded null characters
• return a 100-tuple of strings

What should we return if the value is not defined (in most locales) -- empty string (current behavior), empty tuple or None?

cc @methane

Linked PRs

• gh-124969: Fix locale.nl_langinfo(locale.ALT_DIGITS) #124974
• gh-124969: Skip the test for ALT_DIGITS also on iOS #125177
• [3.13] gh-124969: Fix locale.nl_langinfo(locale.ALT_DIGITS) (GH-124974) #125232
• [3.12] [3.13] gh-124969: Fix locale.nl_langinfo(locale.ALT_DIGITS) (GH-124974) (GH-125232) #125284
• gh-124969: Make locale.nl_langinfo(locale.ALT_DIGITS) returning a string again #125774
• [3.13] gh-124969: Make locale.nl_langinfo(locale.ALT_DIGITS) returning a string again (GH-125774) #125804
• [3.12] gh-124969: Make locale.nl_langinfo(locale.ALT_DIGITS) returning a string again (GH-125774) #125805

[encukou]

@freakboy3742: this fix broke the iOS buildbot. You might have opinions on how to handle this on non-glibc platforms :)

[serhiy-storchaka]

It is interesting that ALT_DIGITS is a FreeBSD extension. And was inherited on Apple platforms. I wonder whether it is not set only for Japanese or for other locales (not installed on buildbots) too? fa_IR, lzh_TW, my_MM, or_IN, shn_MM?

[freakboy3742]

@serhiy-storchaka AFAICT, jp_JP is the only locale in test test set that is defined, and it isn't defining a value for ALT_DIGITS. The others fall back as an unrecognised locale. Whether that can be fixed by installing something else on the buildbot/test machine, I can't say - but I haven't explicitly installed a JP locale on my machine.