[DISCUSSION] Sorting strings in Org mode vs. system locale (was: test-org-table/sort-lines: Failing test on macOS)

[Ihor Radchenko <yantar92@posteo.net>]

Max Nikulin <manikulin@gmail.com> writes:

>> This sounds like something to be adapted to Emacs upstream.
>> I suggested to change `string-collate-lessp' fallback behaviour to use
>> `downcase' when IGNORE-CASE is non-nil. See my last message in
>> bug#59275.
>
> I do not share Eli's position "all or nothing". I prefer graceful 
> degradation and best result achievable with reasonable efforts.

> However either the reason is performance or correctness, both variants 
> are against modification of `string-collate-lessp'. I still think that 
> Org will benefit from a compatibility wrapper with `downcase'.

Unless we have user complaints with real-world use-cases, I am leaning
towards keeping things consistent with Emacs. Including Emacs-wide
fallback for `string-collate-lessp'. This will make our life easier.

Maintaining an Org-specific fallback will (1) cost maintenance time; (2)
may confuse users used to global Emacs behaviour; (3) has no clear
benefit other than our theoretical discussion.

> The only additional consideration is that compare function should be 
> configurable. If a user access same files from Linux and macOS then it 
> may be really annoying to get different order of entries in agenda. For 
> most of Linux users it is better to use more smart 
> `string-collate-lessp'. Some care is required to sort entries obtained 
> from multiple buffers in predictable environment (locale, case 
> conversion table).

I agree. We can introduce a new customization -
`org-string-sort-function' that will be used across Org mode to sort
user text.

It would be even better to allow smart sort function that depends on
document #+language, but I do not see an easy way to implement such
feature - `string-collate-lessp' does accept LOCALE argument, but I have
no idea how to link #+LANGUAGE to locale deterministically.

-- 
Ihor Radchenko // yantar92,
Org mode contributor,
Learn more about Org mode at <https://orgmode.org/>.
Support Org development at <https://liberapay.com/org-mode>,
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