bug#59275: Unexpected return value of `string-collate-lessp' on Mac

[Ihor Radchenko <yantar92@posteo.net>]

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Eli Zaretskii <eliz@gnu.org> writes:

>> > In the strict order of Unicode codepoints?  Use compare-strings.
>> 
>> Thanks for the clarification.
>> After further considerations, it looks like we should still use
>> `string-collate-lessp' on Org side as it yields expected results if libc
>> properly implements the collation.
>
> Is the feature that uses it intended to be used only on glibc platforms
> (which basically means GNU/Linux)?  If not, I'm surprised that you arrived
> at this conclusion.  It is the 180 deg opposite of what I think you should
> have decided.
>
> Once again: locale-specific collation order is inherently unpredictable in
> its results, and should only be used when the locale-specific order is a
> _must_, like when sorting people's names for a telephone directory.

We use string collation for

1. Sorting bibliographies
2. Sorting lists
3. Sorting table lines
4. Sorting tags
5. Sorting headings
6. Sorting entries in agendas
7. As a criterion for agenda/tag filtering when comparison operator is
   used on string property values (11.3.3 Matching tags and properties)

1-6 should follow the locale. I think we had a bug report in the past
where a user got confusing about list sorting being confusing for the
user language conventions.

7 is more debatable.

>> Maybe change
>> 
>>   If your system does not support a locale environment, this function
>>   behaves like `string-lessp'.
>> 
>> to
>> 
>>   Some operating systems do not implement correct collation (in specific
>>   locale environments or at all). Then, this functions falls back to
>>   case-sensitive `string-lessp' and IGNORE-CASE argument is ignored.
>
> Fine with me.

See the attached patch.


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From d9a67e94547ffeb6d8ac8a1202434fff1117af3f Mon Sep 17 00:00:00 2001
Message-Id: <d9a67e94547ffeb6d8ac8a1202434fff1117af3f.1669080246.git.yantar92@posteo.net>
From: Ihor Radchenko <yantar92@posteo.net>
Date: Tue, 22 Nov 2022 09:21:17 +0800
Subject: [PATCH] * src/fns.c (Fstring_collate_lessp): Clarify docstring

Clarify that IGNORE-CASE argument might be ignored when the operation
system does not implement string collation for the specified locale.

See bug#59275.
---
 src/fns.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/fns.c b/src/fns.c
index 035fa12935..e337c0958d 100644
--- a/src/fns.c
+++ b/src/fns.c
@@ -596,8 +596,9 @@ DEFUN ("string-collate-lessp", Fstring_collate_lessp, Sstring_collate_lessp, 2,
 bind `w32-collate-ignore-punctuation' to a non-nil value, since
 the codeset part of the locale cannot be \"UTF-8\" on MS-Windows.
 
-If your system does not support a locale environment, this function
-behaves like `string-lessp'.  */)
+Some operating systems do not implement correct collation (in specific
+locale environments or at all).  Then, this functions falls back to
+case-sensitive `string-lessp' and IGNORE-CASE argument is ignored.  */)
   (Lisp_Object s1, Lisp_Object s2, Lisp_Object locale, Lisp_Object ignore_case)
 {
 #if defined __STDC_ISO_10646__ || defined WINDOWSNT
-- 
2.35.1


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Ihor Radchenko // yantar92,
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